eletrolito ceramico 5

Journal of Power Sources 162 (2006) 3040

Electrolytes for solid oxid

ore Lane 20006

Abstract

The high polytolerance to t of sresponse to FCsrequirement t, whreducing the te malow ohmic l pedlanthanum g the celectrode ma 2006 Else

Keywords: So

1. Introduction

Solid oxide fuel cells (SOFCs) can provide efficient and cleanenergy conversion in a variety of applications ranging from smallauxiliary pmajor advafuel cells (the fuel [3ity, thus lesfuel flexibiture, whichthe rates ofing thermamaterials toimplementare materiaof this pape

The keyionic condtle or no elecontrol of t

Tel.: +1 3E-mail ad

charge carriers is critical. Various approaches for controllingthese transport properties through structure and composition ofthe electrolyte material have been recently reviewed [17]. Theelectrolyte material must also be chemically and mechanically

0378-7753/$doi:10.1016/jower units to large scale power plants [16]. Thentage of SOFCs over polymer electrolyte membranePEMFCs) is their superior tolerance to impurities in9], which allows for their operation using lower qual-s costly and more widely available, fuel. The superiorlity is due primarily to the higher operating tempera-increases reaction rates in the fuel, but also increasesundesired reactions and creates thermal stresses dur-l cycling. Thus, the development and fabrication ofmeet these requirements is a major challenge for the

ation of cost effective SOFCs [1016]. While therels challenges in all fuel cell components, the focusr is on materials for use as the solid electrolyte.requirement for the solid electrolyte is that it has gooduction to minimize cell impedance, but also has lit-ctronic conduction to minimize leakage currents, so

he concentration and mobility of ionic and electronic

34 844 3405; fax: +1 334 844 3400.dress: [email protected].

(e.g. thermal expansion) compatible with other fuel cell com-ponents. This compatibility extends to fabrication processes,since some processes may need to be performed with multi-ple components present, which limit the range of parameters(e.g. temperature or pressure) to those acceptable for all compo-nents. A major impetus for the development of new electrolytematerials is in reducing the operating temperature to 500800 Cfor intermediate temperature solid oxide fuel cells (IT-SOFCs).Such an intermediate operating temperature will relax some ofthe requirements related to high-temperatures operation, whilemaintaining a sufficiently high temperature to retain good fuelflexibility. The focus of this paper is on comparison of the trans-port properties of electrolyte materials for solid oxide fuel cells,but other issues, such as compatibility with electrode materials,will also be discussed.

2. Stabilized zirconia

The most common solid electrolyte material used in solidoxide fuel cells is yttria-stabilized zirconia (YSZ). Yttria is

see front matter 2006 Elsevier B.V. All rights reserved..jpowsour.2006.06.062Jeffrey W. FergusAuburn University, Materials Research and Education Center, 275 Wilm

Received 12 June 2006; received in revised form 20 JuAvailable online 27 July 2

operating temperature of solid oxide fuel cells (SOFCs), as compared toimpurities in the fuel, but also creates challenges in the developmen

these challenges, intermediate temperature solid oxide fuel cells (IT-SOs, which will extend useful lifetime, improve durability and reduce cosoperating temperature of SOFCs is the development of solid electrolyosses during operation. In this paper, solid electrolytes being develoallate-based materials, are reviewed and compared. The focus is onterials, are also discussed.vier B.V. All rights reserved.

lid oxide fuel cells; Electrolytes; Zirconia; Ceria; Gallatese fuel cells

boratories, Auburn, AL 36849, United States06; accepted 21 June 2006

mer electrolyte membrane fuel cells (PEMFCs), improvesuitable materials for the various fuel cell components. In) are being developed to reduce high-temperature materialile maintaining good fuel flexibility. A major challenge interials with sufficient conductivity to maintain acceptably

for solid oxide fuel cells, including zirconia-, ceria- andonductivity, but other issues, such as compatibility with

J.W. Fergus / Journal of Power Sources 162 (2006) 3040 31

Fig. 1. Conductivity of yttria and scandia stabilized zirconia in air at 1000 C[1821].

added to stabilize the conductive cubic fluorite phase, as wellas to increaincrease thconductivit8 mole% adecrease atdefects, whconductivitdopant forhigher condthe conducare shownrespectivelof the rangis includedductivity ofof interest

The higmismatch ibetween Zassociation[21,3840]to increase

Fig. 2. C

Fig. 3. Conduof YSZ condu

tivity of Sc. Thion eacedher srmsohedre isn twd bydopirbiumingses ited tch hae traen shy [2

se insuchZ, ws that, of the t phase may contribute to the higher conductiv-se the concentration of oxygen vacancies, and thuse ionic conductivity. Fig. 1 [1821] shows that they of YSZ increases for yttria additions of up to aboutnd then decreases for higher yttria contents. Thehigher dopant contents is due to association of pointich leads to a reduction in defect mobility and thusy. A promising, although though less widely used,zirconia is scandia, which, as shown in Fig. 1, has auctivity than YSZ. The temperature dependences of

tivities of YSZ and scandia-stabilized zirconia (ScSZ)in Fig. 2 [18,19,2230] and Fig. 3 [20,27,3137],

y. To aid in comparison of the two dopants an outlinee of conductivities for YSZ from Fig. 2 (gray lines)in Fig. 3 (solid black lines) and shows that the con-ScSZ is higher than that of YSZ in the temperatures

for SOFCs.her conductivity of ScSZ is attributed to the smallern size between Zr4+ and Sc3+, as compared to thatr4+ and Y3+, leading to a smaller energy for defect, which increases mobility and thus conductivity. The activation energy for conduction in ScSZ tendswith decreasing temperature, such that the conduc-

500 Cmigratis replfor higtransforhombso thelines iavoideby co-or ytte

Durdecreaattribut, whit phashas betroscopdecreaScSZ,of ScSsame a

amounonductivity of yttria-stabilized zirconia in air [18,19,2230].

ity of ScSZcan be impco-doping

Grain b[27,29,46],with decreaSOFCs. Fodifferent mgrain bounto 040%[27]. Grainnano-structboundary asizes less thhigher thanctivity of scandia-stabilized zirconia in air [20,27,3137]. Rangectivities from Fig. 2.

SZ is similar or even lower than that of YSZ belowis is consistent with the observed increase in thenergy of co-doped zirconia at 380560 C as yttriawith scandia [41]. Another issue with ScSZ is thatcandia contents (e.g. 1012 mole%), the cubic phaseto a rhombohedral phase at lower temperatures. Theral phase has a lower conductivity [20,31,34,36,42],a decrease in conductivity as indicated by broken

o of the curves in Fig. 3. The phase change can belimiting the scandia content to 8 mole% [20,31] or

ng with other oxides, such as those of bismuth [32][36].

operation, aging of both YSZ and ScSZ can lead ton conductivity [21,31,43]. Aging in ScSZ has beeno the disappearance of a distorted fluorite phase [20],s a higher conductivity than the cubic phase [44]. Thensforms to a tetragonal phase, the amount of whichown, with X-ray diffraction [43] and Raman spec-1], to increase during aging. The magnitude of theconductivity during aging is larger for YSZ than forthat, in one study [21], after 5000 h, the conductivityhich was initially about twice that of YSZ, was thet of YSZ. This suggests that the presence, or largerrelative to that of YSZ. The aging behavior in ScSZroved by increasing the scandia content [21] or bywith indium oxide [45].oundary conduction is also important in YSZand since the grain boundary contribution increasessing temperature, it is particularly important for IT-r example, for YSZ materials produced by severalethods, the fraction of the total resistance due to

dary resistance is negligible at 900 C, but increasesat 700 C, and then further to 1065% at 500 C

boundary transport becomes especially important forured materials due to their high proportion of grainrea. For example, processing YSZ to produce grainan 10 nm resulted in conductivities which were 50%those of materials with larger grain sizes [23]. Thus,

32 J.W. Fergus / Journal of Power Sources 162 (2006) 3040

Fig. 4. Condu31,4953]. Ratively.

the benefitsperatures mresistance,

The mec[47] than thin a SOFCchemical plong-life Swith the adniobates [3tivity, so thany resultin

The conare shownranges of corepresentedresulting inbium, whicAlso show(3% yttriathat are compartially stties due toparticles to

Co-dopiproperties.to a reductimina, whicical properdecrease [4ing level. Tto the alumeffects haveNiobium aassociationextend theoccurs, indtion [51]. Tto increase

There are several potential compatibility issues for solid elec-trolytes in SOFCs, since the solid electrolyte is in contact with

ectrog thegenelyterxM

t inlorex 0]. T

s in aon bproced toyer,imenitieslyteceptM [6fro

tratis thea2Zr

t witquir

Theen shlytesLS

rmoequilehav,89,1iumgadma

ion.add

encyctivity of fully- and partially-stabilized zirconia in air [18,19,29nges of YSZ and ScSZ conductivities from Figs. 2 and 3, respec-

of small particle sizes in reducing processing tem-ust be balanced against increased grain boundary

particularly at lower operating temperatures.hanical properties of ScSZ are similar [31] or betterose of YSZ. Although the strength of an electrolyteis of secondary importance as compared to electro-

roperties, it is important for the production of reliableOFCs. The strength and toughness can be improveddition of oxide dispersants, such as alumina [48] or0]. However, such additions typically reduce conduc-e benefits in improved strength must be balanced withg increases in cell impedance.ductivities of zirconia stabilized with other dopantsin Fig. 4 [18,19,2931,4953]. For comparison, thenductivities for YSZ and ScSZ from Figs. 2 and 3 arewith black and gray lines, respectively. The dopantthe highest conductivity among those shown is ytter-h has conductivities comparable to ScSZ and YSZ.

n are some examples of partially stabilized zirconiaor 3% ytterbia), some of which have conductivitiesparable to fully stabilized zirconia. The advantage of

abilized zirconia is the improved mechanical proper-toughening from the transformation of the tetragonal

both elAmonrial iselectroLa1xScontenpyroch(0.3 [7783tions iReactiduringobservtion lais detrductivelectroally acand LSganeseconcen

exceedform Lto startime revalue.has beelectroin YSZby thenot inThe b[76,83as calcdopedyttriumformat

Thea tendthe monoclinic phase.ng can also be used to improve the electrochemicalFor example, the addition of calcium to YSZ can leadon in the activation energy for conduction [54]. Alu-h as mentioned above can be used to improve mechan-ties, has been shown to both increase [48,55,56] and8,57] the conductivity of YSZ, depending on the dop-he beneficial effects of alumina have been attributedina scavenging silica [55], while the detrimentalbeen attributed to increasing defect association [57].

dditions have also been shown to increase defect[58,59], while ceria additions have been shown toyttria content at which a decrease in conductivityicating a decrease in the amount of defect associa-he addition of bismuth oxide to ScSZ has been shownthe conductivity of ScSZ [32].

rial, La1xLa2Zr2O7[6972,109YSZ, and Stance [117,The reactioby inhibitinsimilarly [6to LSC. Anot typicallexpected, Lof other laLSC, but tdue to thecathode mform La2Zdes, the sealant and, in some cases, the interconnect.se, for YSZ, chemical reaction with the cathode mate-rally of greatest concern. The most common SOFCcathode combination is a YSZ electrolyte with anO3 (LSM) cathode. Depending on the strontiumthe LSM, the YSZ and LSM can react to form theLa2Zr2O7 (x 0.2) [6080], the perovskite SrZrO3.4) [7781], or both La2Zr2O7 and SrZrO3 (x 0.5)

he stability of both phases at intermediate composi-greement with thermodynamic calculations [84,85].etween YSZ and LSM is typically only a problemessing at high temperatures, but La2Zr2O7 has beenform during cell operation at 900 C [86]. The reac-

whether formed during processing or cell operation,tal to fuel cell performance [74], because the con-of the reaction products are lower than those of theand electrode materials [67,68,8688]. The gener-

ed reaction mechanism for the reaction between YSZ0,61,65,8890] is that preferential diffusion of man-

m LSM into the YSZ leads to an increase in theon of La2O3 in the LSM. Once the concentrationsolubility limit in LSM, La2O3 reacts with YSZ to

2O7. Thus, one approach to inhibiting this reaction ish a higher manganese content, which will extend theed to decrease the manganese content to the criticaluse of A-site deficient (i.e. lanthanum deficient) LSMown to suppress La2Zr2O7 formation between YSZand LSM electrodes [64,65,74,76,77,88,9196] andM composites [9799]. The approach is supported

dynamic calculations indicating that La2Zr2O7 isibrium with lanthanum-deficient LSM [84,100,101].ior of other manganites is similar to that of LSM02108], although some of these materials, such

-doped lanthanum manganite [76,83,89], strontium-olinium manganate [83,105] and strontium-dopednganate [106], have a weaker tendency for pyrochlore

ition of cobalt to LSM increases reactivity [107,108],that is continued in another SOFC cathode mate-

SrxCoO3 (LSC). Like LSM, LSC reacts to formand/or SrZrO3, depending on strontium content114]. LSC reacts more strongly than LSM withrZrO3 [115,116], as well as increases in cell resis-

118], have been observed during fuel cell operation.n between LSC and YSZ can also affect fabricationg sintering [119]. Other lanthanide cobaltites behave972,107], but some less strongly [120] as comparednother cathode material La1xSrxFeO3 (LSF) doesy react with YSZ [6972,113,121,122]. As might bea1xSrxCo1yFeyO3,(LSCF), and cobaltite ferrites

nthanide and rare-earth elements, react similarly too a lesser extent [6972,107,123126], presumablylower cobalt oxide activity. Finally, another SOFCaterial, LaNi1xFexO3 (LNF), reacts with YSZ tor2O7 [70,127130].

J.W. Fergus / Journal of Power Sources 162 (2006) 3040 33

Fig. 5. Conduand ScSZ con

3. Doped

Like zirmon electrceria has atures, anddisadvantagtial pressurincrease cotivity occucerium is gity of the m(CGO) [37Fig. 2) andductivitiesScSZ. Likedopant conand then detivity for 0low temperperature, soof conductare similar,bility thanPerformancis importanused.

In additother dopa[38,135,15163]. Fig. 6conductivitlower ranggray line).typically loco-dopingthe additioium (replac[164]. Ce1as benefits

Cond]. Ran

160]eporh the[166with8]. Fto lotivitanc

e tonefitwithimp

t inof cef eitdomnismtribucerin, zals ins deshougis inctivity of Ce1xGdxO2x/2 in air [37,136141]. Ranges of YSZductivities from Figs. 2 and 3, respectively.

ceria

conia, ceria forms the fluorite structure and is a com-olyte material for SOFCs. As compared to zirconia,

higher conductivity, particularly at low tempera-a lower polarization resistance [131]. The primarye of ceria is electronic conduction at low oxygen par-

es [37,38,131,132]. Like zirconia, ceria is doped tonductivity, and, also like zirconia, the highest conduc-rs for ions with the lowest size mismatch, which foradolinium and samarium [133135]. The conductiv-ost widely used ceria-based electrolyte, Ce1xGdxO2,136141], is compared with those of YSZ (fromScSZ (from Fig. 3) in Fig. 5. Below 600 C, the con-of CGO are consistently higher than those of YSZ orzirconia, the conductivity increases with increasing

centration to a maximum (e.g. 0.200.25 Gd [141])creases. There is a report [142] of very high conduc-.6 Gd, but the sample in that study was deposited asature, and not subsequently treated at a higher tem-the stability of the structure is not certain. The range

ivities in Fig. 5 for Ce0.9Gd0.1O2 and Ce0.8Gd0.2O2and Ce0.9Gd0.1O2 has been shown to have better sta-Ce0.8Gd0.2O2 at low oxygen partial pressure [136].e of the electrolyte at low oxygen partial pressures

Fig. 6.160,161

cium [been rthrougability

As[46,16to leadconducperformceptiblany beanced

Theevidenlayersthose otion ismechawas atabove,additiomateriCe4+ i

Altsurest [131,135,137,143,144], so both compositions are

ion to gadolinium and samarium [26,135,145154],nts for ceria include lanthanum [155157], yttrium8160], ytterbium [161] and neodymium [153,162,

[26,135,145151,155,156,160,161] shows that theies of Ce1xSmxO2 (CSO) are similar to, but in thee of, the conductivities of CGO (represented by theThe conductivities of ceria with the other dopants arewer than those of CGO or CSO. As with zirconia,can be used for improving properties. For example,n of praseodymium (replaces cerium) and samar-es gadolinium) increases the conductivity of CGOxYxO2 (CYO) is particularly amenable to co-dopingof co-doping of yttria with samarium [147], cal-

ceria with chas been shincluding aLSM, LSCof this excinterlayersreaction [1but CSO ostability ofbetween biity of CGO[181183],When usedinterface at[70,72,117uctivity of Ce1xMxO2x/2 in air [26,135,145151,155,156,ge of CGO conductivities from Fig. 5.

, lithium + cesium [160] and dysprosium [165] haveted. Dopants can also indirectly improve propertiesir effects on processing, such as improving sinter-,167].zirconia, grain boundary conduction is important

or example, reduction of grain size has been shownwer total conductivity of CSO [148] and higher holey in CGO [163], both of which are detrimental toe. In addition, small grained materials are more sus-

reduction in low oxygen partial pressures [37]. Thus,s of reduced grain sizes in processing must be bal-possible detrimental effects on materials properties.ortance of interfaces on transport properties is alsoa nanostructured material consisting of alternatingria and zirconia, which has a conductivity higher thanher of the two constituents indicating that the conduc-inated by the interfacial layers [169]. Although theis not completely understood, the high conductivity

ted to strain enhancing ionic mobility. As mentioneda additions can be used as a co-dopant with yttria. Inirconiaceria solutions can be used as SOFC anode

which the electronic conduction due to reduction ofirable [170].h the stability of ceria in low oxygen partial pres-ferior to that of zirconia, the chemical stability of

athode materials is superior to that of zirconia. CGOown to be stable with a wide variety of electrodes,ll the common cathode materials discussed above,, LSF, LSCF, LNF [6972,123,171,172]. Becauseellent stability with cathode materials, ceria-basedare applied between YSZ and the cathode to prevent14,117,121,173179]. CGO is most commonly used,r CYO are also effective. One exception to the goodceria is that an unidentified phase has been observedsmuth-doped ceria and LSCF [180]. The good stabil-has led to its use in composites cathodes with LSMwhich improves oxygen transport in the cathode.as an interlayer between YSZ and the cathode, thewhich interaction occurs is the YSZceria interface

,121,178,184,185]. Since both phases form the same

34 J.W. Fergus / Journal of Power Sources 162 (2006) 3040

Fig. 7. Conductivity of La0.9Sr0.1Ga0.8Mg0.2O3 in air [26,145,187193].Ranges of YSZ, ScSZ and CGO conductivities from Figs. 2, 3 and 5, respectively.

cubic fluorite structure, interdiffusion can occur and results inthe formation of a region with low conductivity due to orderingof cations.

4. Strontiu

The peand magnduce a maductivityLa0.9Sr0.1Gwith the ra(from Fig. 3The conducand similarnot have anCGO for uof LSGM d27 differenwas for La0[187]. Fig.ties of seve(including

Fig. 8. ConduRange of La0

Fig. 9. Conductivity of La1xSrx(Ga0.8Mg0.2)1y(Co or Fe)yO3 in air [190].

in the same range as those for La0.9Sr0.1Ga0.8Mg0.2O3 in Fig. 7,but there are a few values above and below this range. For com-parison wi

ig. 7this

ofis

0,19th d

raturoth dentae hol, paeme

700.05

ity wl addpedat bye larse inthem/magnesium-doped lanthanum gallate

rovskite, LaGaO3, can be doped with strontiumesium, La1xSrxGa1yMgyO3 (LSGM), to pro-terial with good low-temperature oxygen-ion con-[186]. The conductivities of one composition,a0.8Mg0.2O3, from several sources are shown, alongnges of conductivities of YSZ (from Fig. 2), ScSZ) and CGO (from Fig. 5), in Fig. 7 [26,145,187193].tivity of LSGM is higher than those of YSZ and ScSZto or lower than that of CGO. However, LSGM doeseasily reducible ion, like Ce4+, and thus is superior to

se in low oxygen partial pressures. The conductivityepends on dopant concentration and comparison of

t compositions indicated the maximum conductivity.8Sr0.2Ga0..85Mg0.15O3 and La0.8Sr0.2Ga0.8Mg0.2O38 [187,189191,194200] compares the conductivi-ral LSGM compositions. Most of these conductivitiesthe maximum values reports by Liu et al. [187]) are

from Ffall in

OneLSGM[26,19that botempeever, bdetrimthat thdopingimprovple, atfrom 0ductivoptimaing imcurren

has thincreaFe hasctivity of La1xSrxGa1yMgyO3 in air [187,189191,194200]..9Sr0.1Ga0.8Mg0.2O3 conductivities from Fig. 7. Fig. 10. Condth other materials in subsequent figures, the rangewill be used to represent LSGM, since most values

range.the approaches to increasing the conductivity ofto add transition metal dopants, such as cobalt9,201,202] and iron [26,190,203]. Fig. 9 [190] showsopants increase the conductivity, especially at lowes, with cobalt being more effective than iron. How-opants also decrease the hole conductivity, which is

l to fuel cell performance. Fig. 10 [199,201] showse contribution in cobalt-doped LSGM increases withrticularly at higher temperatures, but the marginalnt decreases with increasing dopant level. For exam-

800 C, when the cobalt concentration is increasedto 0.10, there is a significant increase in hole con-ith very little change in ionic conductivity. Thus, theition of dopant depends on a balance between reduc-nce by increasing dopant level and reducing leakagedecreasing dopant level. For example, while 0.4 Fegest oxygen permeation rate [204], because of thehole conductivity with increasing iron content, 0.2largest improvement in power density, [205]. Otheructivity of La0.8Sr0.2Ga0.85yMg0.15CoyO3 in air [199,201].

J.W. Fergus / Journal of Power Sources 162 (2006) 3040 35

parameters may need to be adjusted when doping the LSGMelectrolyte. For example, the electrolyte thickness for optimalefficiency iBy balancidoped LSGhas also besimilarly tometals hasorite basedCGO [136,added to CAdditions othe electrodCGO [126]

The reacthat of zircmaterials foing a separinterdiffusisome diffuever, the mwhich is tnot the maj[215217])LSCF [217Since smalcial to elecformed at tnecessarilyexcessive ities of bothprevent coba resistive pfuel cell pe

The mosinteractionYSZ electrtive phaseanode [186including povskite cata new phas(La,Sr)(Cr,resistive phsintering tithe processformation oso one ofopment ofsingle-phas

5. Other e

The exisovskite strexample, amon dopan

CondGO a

ed wariumwhiatur

thane ata0.1Gin Fs, in

re ox

mat, L

lytesalumotenton-cnvesvantrted

vapo3, wf safor u

iumyttria co-doped barium cerate is particularly high.proton-conducting oxides for potential use in solid oxidells include BaSc0.5Zr0.5O3 [233], (La,Pr)0.9Ba1.1GaO3.95nd Nd0.9Ba1.1GaO3.95 [237].

muth oxide has high ionic conductivity, but decomposesoxygen partial pressures, which prevents it from being

n solid oxide fuel cells. One approach to overcomingitation is to combine doped bismuth oxide with a ceria-

electrolyte, such that the ceria is at the anode and theh oxide is at the cathode [149,150,238]. If the thick-are selected appropriately, the bismuth oxide will remainits decomposition oxygen partial pressure and the elec-conduction in the ceria will be blocked by the bismuthBismuth oxide can also be doped to stabilize the conduc-ase to lower oxygen partial pressures and temperatures.nductivity of one such phase, Bi3Nb0.1Zr0.9O6.55 [239] isncreases with increasing cobalt dopant level [206].ng these parameters, efficient fuel cells with cobalt-M electrolyte have been produced [207,208]. Nickel

en used as a dopant for LSGM [209,210] and behavescobalt. A similar approach of doping with transitionbeen used to improve the performance of cubic flu-electrolytes. For example, cobalt has been added to139], CSO [211] and YSZ [212], and iron has beenGO [138] to improve processing and conductivity.f iron and cobalt introduced through interaction withe materials have been shown to enhance sintering of.

tion of LSGM with SOFC cathodes is different fromonia or ceria, because most of the common cathoderm the perovskite structure. Thus, rather than form-ate phase, the interaction typically occurs throughon. For example, when used with an LSM cathode,sion of manganese into LSGM occurs [213]. How-ost common diffusing species is cobalt [213221],

he primary diffusing species even if the cobalt isor species in the cathode (e.g. (Ln,Sr)Mn0.8Co0.2O3. Interdiffusion also occurs between LSGM and,222,223] and lanthanum nickelate [224] cathodes.l amounts of cobalt, iron and nickel can be benefi-trolyte performance, and no highly resistive layer ishe electrolytecathode interface, interdiffusion is notdetrimental to fuel cell performance. Nonetheless,

nterdiffusion would eventually degrade the proper-components, so a ceria layer has been applied to

alt diffusion from LSC into LSGM [225]. However,hase can form between CGO and LSGM and degraderformance [226,227].t common anode material is a nickel-YSZ cermet, soanodeelectrolyte interaction is not a problem witholytes. However, for a LSGM electrolyte, a resis-can form between the LSGM and a Ni-containing]. Alternative anode materials are being developed,erovskite oxides, which could, as in reaction with per-hode, result in interdiffusion rather than formation ofe. For example, interdiffusion between LSGM and aMn)O3 anode material during processing can lead toase. Such degradation can be avoided by limiting theme and temperature [228]. However, restrictions oning conditions can be a problem for LSGM, becausef a single-phase perovskite structure can be difficult,

the challenges for LSGM electrolytes is the devel-cost-effective processes for fabricating the desirede microstructures.

lectrolytes

tence of two differently-sized cation sites in the per-ucture expands the range of possible dopants. Forlthough strontium and magnesium are the most com-ts for lanthanum gallate, the lanthanum site can also

Fig. 11.ScSZ, C

be dopwith bangle,temperlowerthe casLa0.9Bshownovskiterials atrolytegalliumelectroity ofother p

Probeen ithe adtranspowaterBaCeOthose o[236],neodymOtherfuel ce[237] a

Bisat lowused ithis limbasedbismutnesses

abovetronicoxide.tive phThe couctivity of perovskite oxides in air [192,229233]. Ranges of YSZ,nd LSGM conductivities from Figs. 2, 3, 5 and 7, respectively.

ith barium [191,192] or gadolinium [229]. Doping, rather than strontium, affects the octahedral tilt

ch reduces the activation energy, such that at highes the conductivity of La0.9Ba0.1Ga0.8Mg0.2O2.85 isthat of La0.9Sr0.1Ga0.8Mg0.2O2.85, but the reverse islower temperatures [191,192]. The conductivity ofa0.8Mg0.2O2.85 and other perovskite materials are

ig. 11 [192,229233]. Other lanthanum-based per-cluding LaScO3-, LaInO3- and LaYO3-based mate-ygen ion conductors [38] and thus potential elec-

erials. Due to the lower cost of aluminum relative toaAlO3-based materials are particularly attractive as

for solid oxide fuel cells [230]. Although the stabil-inates is very good, their conductivity is lower thantial materials (e.g. La0.9Ba0.1Al0.9Y0.1O3 in Fig. 11).onducting or mixed-ion-conducting oxides have

tigated as electrolytes in fuel cells [234]. One ofages of such fuel cells is that, since hydrogen isthrough the electrolyte, the fuel is not diluted withr. The most common proton-conducting oxide ishich has been doped with various oxides, including

marium [231], neodymium [232,235] and ytterbiumse in SOFCs. Fig. 11 shows that the conductivity of

36 J.W. Fergus / Journal of Power Sources 162 (2006) 3040

Fig. 12. CondCGO and LSG

shown in F-Bi2O3, bbe evaluate

Also shstructure basium. The cwith increastitial cond[240242]the oxygen

AnotherLa2Mo2O9good condudramaticallelectronic cbe a proble

Anothertrolyte matthis structuthe same stgests thatthe most htitanates anabove, La2different elNonethelesinvestigate

6. Conclu

The twoin IT SOFChas the higmaterials, bsures. LSGwith the andesigns withe differereduce cosdepends on

anode supported), and compatibility (chemical and mechanical)depends on the materials used for other components, so these

, mumat

nce

.Q. M.C. W

. Sing.C. Si.Q. M.A.J.. Tu,. Sasa

eram.

. Lam(3) (2.C.H..C.H..C.H.. Tiet4654. Yok1713.P.S. B.Q. Mciencaster,.R. Hochem.W. SM. Dochem.P.S. B000). Nomtate Io. Guo3 (200. Xinlloys. Hae59.H. JoOFC. Ishihrocee. Yamuctivity of various oxides in air [239244]. Ranges of YSZ, ScSZ,M conductivities from Figs. 2, 3, 5 and 7, respectively.

ig. 12. The phase is stable to lower temperatures thanut the low oxygen partial pressure stability needs tod.own in Fig. 12 are three materials with the apatitesed on doping La10Si6O27 with aluminum or magne-onductivity of materials with this structure increasessing oxygen stoichiometry, which suggests an inter-uction mechanism [38]. The three examples in Fig. 12illustrate this trend as the conductivity increases ascoefficient increases from 26 to 26.1 to 26.75.class of solid electrolytes are materials based on

. The two examples shown in Fig. 12 [243,244] havectivity at 600700 C, but the conductivity decreasesy with decreasing temperature. The possibility ofonduction at low oxygen partial pressures may alsom.structure that has been investigated for potential elec-erials is the pyrochlore structure. The similarity ofre with the cubic fluorite structure (i.e. essentiallyructure with one oxygen missing per unit cell) sug-it may be a good oxygen ion conductor. However,ighly conductive materials with the pyrochlore ared thus exhibit electronic conduction. As mentionedZr2O7 forms from the reaction of YSZ and severalectrodes and has a low conductivity relatively to YSZ.

factorstrolyte

Refere

[1] N[2] M[3] P[4] S[5] N[6] M[7] H[8] K

c

[9] P3

[10] B[11] B[12] B[13] F

4[14] H

1[15] S[16] N

Sc

[17] Str

[18] D[19] J.

tr[20] S

(2[21] K

S[22] X

5[23] X

A[24] C

2[25] J.

S[26] T

P[27] Ks, electrolytes with the pyrochlore structure are beingd for use in SOFCs [245,246].

sions

most widely used alternatives to YSZ as electrolytess are doped ceria and doped lanthanum gallate. Ceriahest conductivity and the best stability with cathodeut suffers from stability in low oxygen partial pres-

M has higher conductivity than YSZ, but is less stableode and more difficult to prepare than YSZ. Fuel cellth layered structures can combine the advantages ofnt materials, but simple structures are preferred tot and improve reliability. The required conductivitythe fuel cell design (e.g. electrolyte-supported versus

Society[28] M. Bec

ety Pro[29] X. Guo[30] T.-H. Y[31] O. Yam

Y. Nak[32] S. Sara[33] C. Hae

(2005)[34] D.-H. P

Hilpertpp. 947

[35] J.T.S. I2005-0

[36] R. Chib[37] M. Mo

ety Prost be considered in the selection of the optimal elec-erial for a particular application.

s

inh, J. Am. Ceram. Soc. 76 (3) (1993) 563588.illiams, Fuel Cells 1 (2) (2001) 8791.

h, N.Q. Minh, Int. J. Appl. Ceram. Technol. 1 (1) (2004) 515.nghal, Solid State Ionics 152153 (405) (2003) 405410.inh, Solid State Ionics 174 (2004) 271277.Cropper, J. Power Sources 131 (2004) 5761.U. Stimming, J. Power Sources 127 (12) (2004) 284293.ki, K. Watanabe, K. Shiosaki, K. Susuki, Y. Teraoka, J. Electro-13 (2004) 669675.p, J. Tachtler, O. Finkenwirth, S. Mukerjee, S. Shaffer, Fuel Cells003) 146152.Steele, J. Mater. Sci. 36 (2001) 10531068.Steele, A. Heinzel, Nature 414 (6861) (2001) 345352.Steele, Solid State Ionics 134 (1/2) (2000) 320.

z, Mater. Sci. Forum 426432 (Pt 5 THERMEC2003) (2003)470.okawa, H. Sakai, T. Horita, K. Yamaji, Fuel Cells 1 (2) (2001)1.adwal, K. Foger, Mater. Forum 21 (1997) 187224.inh, in: S.P.S. Badwal, M.J. Bannister, R.H.J. Hannink (Eds.),

e and Technology of Zirconia V, Technomic Publishing Co., Lan-PA, 1993, pp. 652663.ui, J. Roller, X. Zhang, C. Dece`s, Y. Xie, R. Maric, D. Gosh, Elec-

ical Society Proceedings, 2005-07, SOFC IX, 2005, pp. 964977.trickler, W.G. Carlson, J. Am. Ceram. Soc. 47 (3) (1964) 122127.ixon, L.D. LaGrange, U. Mergen, C.F. Miller, J.T. Porter, J. Elec-

. Soc. 110 (4) (1963) 276280.adwal, F.T. Ciacchi, D. Milosevic, Solid. State Ionics 136137

9199.ura, Y. Mizutani, M. Kawai, Y. Nakamura, O. Yamamoto, Solidnics 132 (2000) 235239., E. Vasco, S. Mi, K. Szot, E. Wachsman, R. Waser, Acta Mater.5) 51615166.

, Z. Lu, Z. Ding, X. Huang, Z. Liu, X. Sha, Y. Zhang, W. Su, J.Compd., in press.ring, A. Roosen, H. Schichl, Solid State Ionics 176 (2005) 253

o, G.M. Choi, Electrochemical Society Proceedings, 2005-07,IX, 2005, pp. 10511056.ara, M. Enoki, J.W. Yan, H. Matsumoto, Electrochemical Society

dings, 2005-07, SOFC IX, 2005, pp. 11171126.ahara, C.P. Jacobson, S.J. Visco, L.C. De Jonghe, ElectrochemicalProceedings, 2003-07, SOFC VII, 2003, pp. 187195.

ker, A. Weber, A.C. Muller, E. Ivers-Tifee, Electrochemical Soci-ceedings, 2003-07, SOFC VII, 2003, pp. 222228., J. Maier, J. Electrochem. Soc. 148 (3) (2001) E121E126.eh, W.-C. Hsu, C.C. Chou, J. Phys. IV France 128 (2005) 213219.amoto, Y. Arati, Y. Takeda, N. Imanishi, Y. Mizutani, M. Kawai,

amura, Solid State Ionics 124 (1995) 137142.t, N. Sammes, A. Smirnova, J. Power Sources, in press.ring, A. Roosen, H. Schichl, M. Schnoller, Solid State Ionics 176261268.eck, R.-H. Song, J.-H. Kim, T.-H. Lim, D.-R. Shin, D.-H. Jung, K., Electrochemical Society Proceedings, 2005-07, SOFC IX, 2005,953.

rvine, T. Politova, A. Kruth, Electrochemical Society Proceedings,7, SOFC IX, 2005, pp. 941946.a, T. Ishii, F. Yoshimura, Solid State Ionics 91 (1996) 249256.

gensen, D. Lybye, K. Kammer, N. Bonanos, Electrochemical Soci-ceedings, 2005-07, SOFC IX, 2005, pp. 10681074.

J.W. Fergus / Journal of Power Sources 162 (2006) 3040 37

[38] V.V. Kharton, F.M.B. Marques, A. Atkinson, Solid State Ionics 174 (2004)135149.

[39] J.W. Fergus, J. Mater. Sci. 38 (21) (2003) 42594270.[40] R. Porn

Phys. 9[41] M. Ku

4846.[42] M. Wel

Solid S[43] A.C. M

Society[44] L.J. Ga[45] J. Kond

149 (8)[46] X. Guo[47] M.M. S

chemic[48] M. Mo

State Io[49] H.A. Jo[50] D.K. H[51] J.-H. L

State Io[52] I.Yu. P

IX, 200[53] E. Djur

ings, 20[54] M.M. B[55] D. Lyb

Procee[56] N.H. M

D. Sto2003, p

[57] X. Guo[58] Z. Wan

12751[59] Z. Wan

(2000)[60] D. Kus

State Io[61] A. Kha[62] H.-K. L[63] D.M. T

Conf. S29930

[64] M.J.L.Acta 40

[65] C. ClauIonics

[66] A. MittElectro17th, R

[67] C. Bru17718

[68] G. Chio[69] J.M. R

State Io[70] J.M. R

ceeding[71] J.M. R

11611[72] J.M. Ra

A1518[73] Y. Ji, J.[74] S.P.S. B[75] S.P. Jia

18651

[76] G. Stochniol, S. Broel, A. Naoumidis, H. Nickel, Fresnius J. Anal. Chem.355 (1996) 697700.

[77] G. Stochniol, E. Syskakis, A. Naoumidis, J. Am. Ceram. Soc. 78 (4)995). Kle. Wii. Wiikoulsenroc. Renma. Wiirande. Gruhem.. Norhys. C.Y. Teram.. Yokannisechno.M.ium +H, 19.Y. L.A. Spng. Pe. Mitt. Taim) (19A.M.0331. Weers-Teramiation.P. Jia002)

.P. Jiaci. 35.P. Jia.P.S. B.G.E.eeding. Tsep.C. PaOFC. Bon. Mo

ochem7th, R. Wan76 (35. Yok) (19. Yok003)-P. Zhhem..-L. W999). An,. Take.B. P

8102.-J. H12.prasertsuk, P. Ramanarayanan, D.B. Musgrave, F.B. Prinz, J. Appl.8 (2005) 1062513-11062513-8.rumada, H. Hara, E. Iguchi, Acta Mater. 53 (2005) 4839

ler, F. Khelfaoui, M. Kilo, M.A. Taylor, C. Argirusis, G. Borchardt,tate Ionics 175 (2004) 329333.uller, A. Weber, D. Herbstritt, E. Ivers-Tiffee, ElectrochemicalProceedings, 2003-07, SOFC VII, 2003, pp. 196199.

uckler, K. Sasaki, Solid State Ionics 75 (1995) 203210.oh, H. Shiota, Y. Tomii, Y. Ito, K. Kawachi, J. Electrochem. Soc.(2002) J59J72., R. Waser, Prog. Mater. Sci. 51 (2006) 151210.eabaugh, M.J. Day, K. Sabolsky, S. Ibanez, S.L. Swartz, Electro-al Society Proceedings, 2005-07, SOFC IX, 2005, pp. 10371044.ri, T. Abe, H. Itoh, O. Yamamoto, Y. Takeda, T. Kawahara, Solidnics 74 (1994) 157164.hansen, J.G. Cleary, J. Electrochem. Soc. 111 (1) (1964) 100103.ohnke, J. Phys. Chem. Solids 41 (1980) 777784.ee, S.M. Yoon, K.-K. Kim, J. Kim, H.-W. Lee, H.-S. Song, Solidnics 144 (2001) 175184.

rokhorov, Electrochemical Society Proceedings, 2005-07, SOFC5, pp. 9981001.ado, F. Boulch, L. Dessemond, Electrochemical Society Proceed-03-07, SOFC VII, 2003, pp. 160168.ucko, Mater. Sci. Poland 24 (1) (2006) 3944.

ye, Y.-L. Liu, M. Mogensen, S. Linderoth, Electrochemical Societydings, 2005-07, SOFC IX, 2005, pp. 954963.enzler, R. Hansch, R. Fleck, G. Bla, H.P. Buchkremer, H. Schichl,

ver, Electrochemical Society Proceedings, 2003-07, SOFC VII,p. 238245., Phys. Stat. Sol. (a) 183 (2) (2001) 261271.g, Z.Q. Chen, S.J. Wang, X. Guo, J. Mater. Sci. Let. 19 (2000)278.g, Z.Q. Chen, J. Zhu, S.J. Wang, X. Guo, Rad. Phys. Chem. 58697701.cer, J. Holc, M. Hrovat, S. Bernik, S. Samardzija, D. Kolar, Solidnics 78 (1995) 7985.ndkar, S. Elangovan, M. Liu, Solid State Ionics 52 (1994) 5768.ee, Mater. Chem. Phys. 77 (3) (2003) 639646.ericker, J.B. Bilde-Srensen, B. Kindl, W.M. Stobbs, Inst. Phys.er 119 (1991) 299302, Electon Microscopy and Analysis (1991)2.stergaard, C. Clausen, C. Bagger, M. Mogensen, Electrochimica

(12) (1995) 19711981.sen, B. Bagger, J.B. Bilde-Srensen, A. Horsewell, Solid State

7071 (1994) 5964.erdorfer, L.J. Gauckler, in: F.W. Poulsen (Ed.), High Temperaturechemistry: Ceramics and Metals, Proc. Ris Int Symp. Mater. Sci.,is National Lab, Roskilde, Denmark, 1996, pp. 357362.gnoni, U. Ducati, M. Scagliotti, Solid State Ionics 76 (1995)2.delli, M. Scagliotti, Solid State Ionics 73 (1994) 265271.

alph, C. Rossignol, R. Kumar, Proc. Electrochem. Soc. 26 (Solid-nic Devices III) (2003) 134144.

alph, J.T. Vaughey, M. Krumpelt, Electrochemical Society Pro-s, 2001-16, SOFC VII, 2001, pp. 466475.

alph, A.C. Schoeler, M. Krumpelt, J. Mater. Sci. 36 (5) (2001)172.lph, C. Rossignol, R. Kumar, J. Electrochem. Soc. 150 (11) (2003)

A1522.A. Kilner, M.F. Carolan, Solid State Ionics 176 (2005) 937943.adwal, Solid State Ionics 143 (2001) 3946.ng, J.P. Zhang, K. Foger, J. Eur. Ceram. Soc. 23 (11) (2003)873.

(1[78] K

K[79] K

PPD

[80] KG

[81] HC

[82] KP

[83] HC

[84] HBT

[85] Hn

O[86] H[87] S

E[88] A[89] H

(2[90] J.

3[91] A

IvCN

[92] S(2

[93] SS

[94] SS

[95] Fc

[96] T[97] S

S[98] N

Mtr1

[99] Z1

[100] H(9

[101] H(2

[102] J.C

[103] T(1

[104] K[105] Y

M2

[106] T2929932.veland, M.-A. Einarsrud, C.R. Schmidt, S. Shamsili, S. Faaland,k, T. Grande, J. Am. Ceram. Soc. 82 (3) (1999) 729734., C.R. Schmidt, S. Shamsili, M.-A. Einarsrud, T. Grande, in: F.W.(Ed.), High Temperature Electrochemistry: Ceramics and Metals,is Int Symp. Mater. Sci., 17th, Ris National Lab, Roskilde,

rk, 1996, pp. 491496.k, C.R. Schmidt, S. Faaland, S. Shamsili, M.-A. Einarsrud, T., J. Am. Ceram. Soc. 82 (3) (1999) 721728.bmeier, A. Naoumidis, G. Stochniol, A. Tsoga, Fresnius J. Anal.353 (1995) 393398.d-Varhaug, S.J. Andersen, K. Wiik, R. Hier, . Johannesen, Inst.onf. Ser 119 (Electon Microscopy and Analysis) (1991) 295298.

u, W.Y. Sun, Y.J. Yang, Z.Y. Lu, D.Q. Wang, T.L. Wen, J. Eur.Soc. 20 (1415) (2000) 24212425.

okawa, N. Sakai, T. Kawada, M. Dokiya, in: S.P.S. Badwal, M.J.ter, R.H.J. Hannink (Eds.), Science and Technology of Zirconia V,mic Publ. Co, Lancaster, PA, 1993, pp. 752763.Ondik, H.F. McMurdie (Eds.), Phase Diagrams for Zirco-Zirconia Systems, The American Ceramic Society, Westerville,98, p. 342, Figure, Zr-474.

ee, S.M. Oh, Solid State Ionics 90 (1996) 133140.eakman, R.D. Carneim, E.A. Payzant, T.R. Armstrong, J. Mater.rf. 13 (3) (2004) 303308.erdorfer, L.J. Gauckler, Solid State Ionics 111 (1998) 185218.atsu, K. Wada, H. Kaneko, H. Yamamura, J. Am. Ceram. Soc. 75

92) 401405.van Roosmalen, E.H.P. Cordfunke, Solid State Ionics 5 (1992)2.

ber, R. Maenner, B. Jobst, M. Schiele, H. Cerva, R. Waser, E.ifee, in: F.W. Poulsen (Ed.), High Temperature Electrochemistry:cs and Metals, Proc. Ris Int Symp. Mater. Sci., 17th, Risal Lab, Roskilde, Denmark, 1996, pp. 473478.ng, Electrochem. Soc. Proc. Vol. 26 (Solid-State Ionic Devices III)145154.ng, J.P. Zhang, Y. Ramprakash, D. Milosevic, K. Wilshier, J. Mater.(2000) 27352741.

ng, J.G. Love, J.P. Zhang, M. Hoang, Y. Ramprakash, A.E. Hughes,adwal, Solid State Ionics 121 (1999) 110.

Jones, P.A. Connor, J.T.S. Irvine, Electrochemical Society Pro-s, 2005-07, SOFC IX, 2005, pp. 15711577.in, S.A. Barnett, Solid State Ionics 93 (1997) 207217.ulson, V.I. Birss, Electrochemical Society Proceedings, 2003-07,VIII, 2003, pp. 498508.anos, C.C. Appel, in: F.W. Poulsen, N. Bonanos, S. Linderoth,gensen, B. Zachau-Christiansen (Eds.), High Temperature Elec-istry: Ceramics and Metals, Proc. Ris Int. Symp Mater. Sci.,

is National Lab, Roskilde, Denmark, 1996, pp. 181186.g, M. Cheng, Y. Dong, M. Zhang, H. Zhang, Solid State Ionics36) (2005) 25552561.

okawa, N. Sakai, T. Kawada, M. Dokiya, J. Electrochem. Soc. 13891) 27192727.okawa, Proc. Electrochem. Soc. 26 (Solid-State Ionic Devices III)115.ang, S.-P. Jiang, J.G. Love, K. Foger, S.P.S. Badwal, J. Mater.

8 (1998) 27872794.en, H. Tu, Z. Xu, O. Yamamoto, Solid State Ionics 121 (14)

2530.K.L. Reifsnider, C.Y. Gao, J. Power Sources 158 (2006) 254262.da, H.Y. Tu, H. Sakaki, S. Watanabe, N. Imanishi, O. Yamamoto,hillipps, N.M. Sammes, J. Electrochem. Soc. 144 (8) (1997)816.uang, Y.-S. Huang, Mater. Sci. Eng. B B103 (3) (2003) 207

38 J.W. Fergus / Journal of Power Sources 162 (2006) 3040

[107] H.Y. Tu, X.H. Lu, T.L. Wen, Y. Takeda, T. Ichikawa, N. Imanishi, O.Yamamoto, J. Australasian Ceram. Soc. 35 (12) (1999) 16.

[108] H.Y. Tu, M.B. Phillipps, Y. Takeda, T. Ichikawa, N. Imanishi, N.M.Samme2091.

[109] J. Fleig[110] K.C. W[111] L.J. Ga

J.L. Ru[112] F.M. Fi

Ionics[113] S.P. Si

Ionics[114] H.J. Hw

ceeding[115] M. Sas

Phys. C[116] R. Zhe

140 (2)[117] S. Char

(1999)[118] Y. Ohn

Monmand Tecpp. 724

[119] T.J. AA515

[120] K.T. Le[121] C. Ros

(14) ([122] M.D. A

(2004)[123] L. Qiu,

158 (1[124] H.Y. T

(1999)[125] J.Y. Ki

Ceram[126] H. Fuk

Procee[127] R.N. B

(1) (20[128] J. Knud

(2005)[129] H. Oru

(9) (20[130] H. Oru

ings, 2[131] B. Dal

Mogen[132] R.S. G

2003, p[133] K. Sch[134] D.A. A

Johans[135] H. Yah[136] V.V. K

Kovaleques, J

[137] S. Wan147 (10

[138] T.S. Zh[139] E. Jud,[140] A. Sin

Siiracu(2004)

[141] D.J. Se41 (200

[142] E. Gourba, A. Ringuedem, N. Cassir, J. Paivasaari, J. Niinisto, M. Putko-nen, L. Niinisto, Electrochemical Society Proceedings, 2003-07, SOFCIX, 2003, pp. 267274.

. Wan998).-D. Zolid Siffusi. Xu,ompd. Yah2753. Shapres

. Jasin-Y. Pa4022-Y. Pa7, SO.-P. Fpres. La

997.. Sam2863. Hiraukudo. Sud1611. Sharess.. Shim005). Harater.. Yuglectro6126. Ma

lectro5326.J. Ho3864. YasMizu. Saktate Io. Torr8368.K. Tarocee. Yos. Mo006). Tsc. Thevanan

005, p. Sakrito,06.. Wal996). Dus. Kawizusa

005, p. Mais, O. Yamamoto, J. Electrochem. Soc. 146 (6) (1999) 2085

, Annu. Rev. Mater. Res. 33 (2003) 361382.incewicz, J.S. Cooper, J. Power Sources 140 (2005) 280296.uckler, D. Beckel, B.E. Buergler, E. Jud, U.P. Muecke, M. Prestat,pp, J. Richter, Chimia 58 (12) (2004) 837850.gueiredo, J.A. Labrincha, J.R. Frade, F.M.B. Marques, Solid State101103 (1997) 343349.mner, J.P. Shelton, M.D. Anderson, J.W. Stevenson, Solid State161 (2003) 118.

ang, J.-W. Moon, Y. Lim, S. Lee, Electrochemical Society Pro-s, 2005-07, SOFC IX, 2005, pp. 16521657.e, D. Ueno, K. Yashiro, A. Kaimai, T. Kawada, J. Mizusaki, J.hem. Solids 66 (2005) 343348.

ng, X.M. Zhou, S.R. Wen, T.-L. Wen, C.X. Ding, J. Power Sources(2005) 217225.ojrochkul, K.L. Choy, B.C.H. Steele, Solid State Ionics 121 (14)107113.o, M. Hata, Y. Kaga, K. Tsukamoto, F. Uchiyama, T. Okuo, A.a, in: S.P.S. Badwal, M.J. Bannister, R.H.J. Hannink (Eds.), Sciencehnology of Zirconia V, Technomic Publ. Co., Lancaster, PA, 1993,732.rmstrong, J.G. Rich, J. Electrochem. Soc. 153 (3) (2006)A520.e, A. Manthiram, J. Electrochem. Soc. 153 (4) (2006) A794A798.

signol, J.M. Ralph, J.-M. Bae, J.T. Vaughey, Solid State Ionics 1752004) 5961.nderson, J.W. Stevenson, S.P. Simner, J. Power Sources 129 (2)188192.T. Ichikawa, A. Hirano, N. Imanishi, Y. Takeda, Solid State Ionics2) (2003) 5565.

u, Y. Takeda, N. Imanishi, O. Yamamoto, Solid State Ionics 117277281.m, N.L. Canfield, L.A. Chick, K.D. Meinhardt, V.L. Sprenkle,. Eng. Sci. Proc. 26 (4) (2005) 129138.unaga, C. Arai, C.-J. Wen, K. Yamada, Electrochemical Societydings, 2001-16, SOFC VII, 2001, pp. 449457.asu, F. Tietz, E. Wessel, D. Stover, J. Mater. Process. Technol. 14704) 8589.sen, P.B. Briehling, N. Bonanos, Solid State Ionics 176 (1718)15631569.i, K. Watanabe, R. Chiba, M. Arakawa, J. Electrochem. Soc. 15104) A1412A1417.i, K. Watanabe, M. Arakawa, Electrochemical Society Proceed-003-07, SOFC VIII, 2003, pp. 571579.slet, P. Blennow, P.V. Hendriksen, N. Bonanos, D. Lybye, M.sen, J. Solid State Electrochem. 10 (2006) 547561.ordon, Electrochemical Society Proceedings, 2003-07, SOFC VII,p. 141152.

warz, Proc. Natl. Acad. Sci. U.S.A. 103 (10) (2006) 3497.ndersson, S.I. Simak, N.V. Skorodumova, I.A. Abrikosov, B.

son, Proc. Natl. Acad. Sci. U.S.A. 103 (10) (2006) 35183521.iro, K. Eguchi, H. Arai, Solid State Ionics 36 (12) (1989) 7175.harton, F.M. Figueiredo, L. Navarro, E.N. Naumovich, A.V.vsky, A.A. Yaremchenko, A.P. Viskup, A. Carneiro, F.M.B. Mar-.R. Frade, J. Mater. Sci. 36 (2001) 11051117.g, T. Koyabashi, M. Dokiya, T. Hashimoto, J. Electrochem. Soc.) (2000) 36063609.ang, J. Ma, L.H. Luo, S.H. Chan, J. Alloys Compd., in press.L.J. Gauckler, J. Electroceram. 15 (2005) 159166.

, Yu. Dubitsky, A. Zaopo, A.S. Arico`, L. Gullo, D. La Rosa, S.sano, V. Antonucci, C. Oliva, O. Ballabio, Solid State Ionics 175361366.o, K.O. Ryu, S.B. Park, K.Y. Kim, R.-H. Song, Mater. Res. Bull.6) 359366.

[143] S(1

[144] XSD

[145] DC

[146] H5

[147] Xin

[148] P[149] J.

2[150] J.

0[151] Y

in[152] W

2[153] S

6[154] Y

F[155] E

1[156] X

p[157] T

(2[158] H

M[159] H

E2

[160] ME2

[161] S6

[162] KJ.

[163] NS

[164] T6

[165] SP

[166] H[167] M

(2[168] A[169] S

th2

[170] NB5

[171] D(1

[172] V[173] T

M2

[174] Ag, H. Inaba, M. Dokiya, T. Hashimoto, Solid State Ionics 1077379.hou, W. Huebner, H.U. Anderson, Diffusion and Defect Data tate Data, Pt. A: Defect and Diffusion Forum 242244 (Defectson Ceramics) (2005) 277289.X. Liu, D. Wang, G. Yi, Y. Gao, D. Zhang, W. Su, J. Alloys

., in press.iro, Y. Eguchi, K. Egushi, H. Arai, J. Appl. Electrochem. 18 (1988)1.

, Z. Lu, X. Huang, J. Miao, L. Ja, X. Xin, W. Su, J. Alloys Compd.,s.ski, Solid State Ionics, in press.rk, H. Yoon, E.D. Wachsman, J. Am. Ceram. Soc. 88 (9) (2005)408.rk, E.D. Wachsman, Electrochemical Society Proceedings, 2003-FC VII (2003) 289298.u, C.-H. Lin, C.-W. Liu, K.-W. Tay, S.-B. Wen, J. Power Sources,s.i, S.M. Haile, J. Am. Ceram. Soc. 88 (11) (2005) 2979

eshima, Y. Hirata, Y. Ehira, J. Alloys Compd. 408412 (2006)1.ta, S. Yokomine, S. Sameshima, T. Shimonosono, S. Kishi, H.me, J. Jpn. Ceram. Soc. 113 (9) (2005) 597604.a, P. Pacaud, M. Mori, J. Alloys Compd. 408412 (2006)164.

, Z. Lu, X. Huang, J. Miao, Z. Ding, W. Su, J. Alloys Compd., in

onosono, Y. Hirata, S. Sameshima, J. Am. Ceram. Soc. 88 (8)21142120.tmanova, E.E. Lomonva, V. Natratil, P. Sutta, F. Kundracik, J.Sci. 40 (2005) 56795683.ami, Y. Endo, T. Yokobori, T. Otake, T. Kawada, J. Mizusaki,chemical Society Proceedings, 2003-07, SOFC VII, 2003, pp.6.

rrero-Cruz, E.P. Hong, C.P. Jacobson, S.J. Visco, L.C. De Jonghe,chemical Society Proceedings, 2003-07, SOFC VII, 2003, pp.0.ng, K. Mehta, A.V. Virkar, J. Electrochem. Soc. 145 (2) (1998)7.

hiro, T. Suzuki, A. Kaimai, H. Matsumoto, Y. Nigara, T. Kawada,saki, J. Sfeir, J. Van herle, Solid State Ionics 175 (2004) 341344.

ai, Y.P. Xiong, K. Yamaji, H. Yokokawa, Y. Terashi, H. Seno, Solidnics, in press.ens, N.M. Sammes, G. Tompsett, J. Electroceram. 13 (2004)9.dokoro, R. Muccillo, E.N.S. Muccillo, Electrochemical Society

dings, 2005-07, SOFC IX, 2005, pp. 10751080.hida, T. Inagaki, J. Alloys Compd. 408412 (2006) 632636.ri, E. Suda, B. Pacaud, K. Murai, T. Moriga, J. Power Sources 157688694.hope, J. Electroceram. 14 (2005) 523.uthasan, L.V. Saraf, S. Azad, O.A. Marina, C.M. Wang, V. Shut-

dan, Electrochemical Society Proceedings, 2005-07, SOFC IX,p. 978985.ai, Y.P. Xiong, K. Yamaji, H. Kishimoto, T. Horita, M.E.H. Yokokawa, J. Alloys Compd. 408412 (2006) 503

ler, J.A. Lane, J.A. Kilner, B.C.H. Steele, Solid State Ionics 8688767772.astre, J.A. Kilner, Solid State Ionics 126 (1999) 163174.ada, D. Ueno, M. Sase, K. Yashiro, T. Otake, A. Kaimai, J.ki, Electrochemical Society Proceedings, 2005-07, SOFC IX,p. 16951702., V.A.C. Haanappel, F. Tietz, D. Stover, Solid State Ionics, in press.

J.W. Fergus / Journal of Power Sources 162 (2006) 3040 39

[175] M. Shiono, K. Kobayashi, T.L. Nguyen, K. Hosoda, T. Kato, K. Ota, M.Dokiya, Solid State Ionics 170 (12) (2004) 17.

[176] T.L. Nguyen, T. Honda, T. Kato, Y. Iimura, K. Kato, A. Negishi, K.NozakiElectro

[177] T.L. NK. NozKato, S

[178] A. Tso(2000)

[179] N. Saical S1707.

[180] H. Zha(1) (20

[181] S.P. Jia[182] E.P. M

273.[183] J. Zhan

32232[184] A. Tso

40340[185] A. Tso

(1999)[186] A.V. Jo

(2004)[187] M. Liu

Sci., in[188] I. Yasu

(2000)[189] J.W. St

S. Bask[190] J.W. S

trochem[191] J.W. St

Weber,[192] J. Brad

Procee[193] M. Ohn[194] M. Kur

(2005)[195] T. Mat

(2000)[196] Z.-C. L

23572[197] M. Shi,

in pres[198] T. He,

26642[199] B.A. K

(2006)[200] B. Ram[201] T. Ishih

Ionics[202] T. Ishih

Solid S[203] M. Eno[204] T. Ishih

J. Elect[205] T. Ishih

(2006)[206] T. Ishih

Takita,[207] T. Inag

M. Ya517.

[208] T. YamK. Ada

H. Yoshida, M. Kawano, T. Sasaki, T. Inagaki, K. Miura, T. Ishihara, Y.Takita, J. Electrochem. Soc. 151 (10) (2004) A1712A1714.

[209] A.A. Yaremchenko, V.V. Kharton, E.N. Naumovich, D.I. Shestakov, V.F.hukha.M.B.. Ishihnics

. Pere478. Den005-0. Huaoc. 14.X. Cater.. Che

3191. NaoAnal.C. Ktover,. Horiolid S. Arguller

OFC. Mahang,I, 199agak

ukui,p. 963.L. S004). Sak. Mats621.N. Muel C. Bi, M005). Hro

4 (12. Hua001). Du,OFC. Kaj

.-Y. COFC. Ranr8939.-T. S77 (20. Kob005)

. Scho. Gorower. Tahe6216. Ken005-0.J. Le005-0. Kro. Oss39., M. Shiono, A. Kobayashi, K. Hosoda, Z. Cai, M. Dokiya, J.chem. Soc. 151 (8) (2004) A1230A1235.guyen, K. Kobayashi, T. Honda, Y. Iimura, K. Kato, A. Negishi,aki, F. Tappero, K. Sasaki, H. Shirahama, K. Ota, M. Dokiya, T.olid State Ionics 174 (14) (2004) 163174.ga, A. Gupta, A. Naoumidis, P. Nikolopoulos, Acta Mater. 4847094714.kai, H. Yokokawa, M. Miyachi, A. Sawata, Electrochem-ociety Proceedings, 2005-07, SOFC IX, 2005, pp. 1703

o, L. Huo, L. Sun, L. Yu, S. Gao, J. Zhao, Mater. Chem. Phys. 8804) 160166.ng, W. Wang, Solid State Ionics 176 (2005) 13511357.urray, S.A. Barnett, Solid State Ionics 143 (2001) 265

g, Y. Ji, H. Gao, T. He, J. Liu, J. Alloys Compd. 395 (12) (2005)5.ga, A. Naoumidis, D. Stover, Solid State Ionics 135 (2000)9.ga, A. Naoumidis, W. Jungen, D. Stover, J. Eur. Ceram. Soc. 19907912.shi, J.J. Steppan, D.M. Taylor, S. Elangovan, J. Electroceram. 13619625., M. Shi, C. Wang, Y.P. Yuan, P. Majewski, F. Aldinger, J. Mater.press.

da, Y. Matsuzaki, T. Yamakawa, T. Koyama, Solid State Ionics 135381388.evenson, T.R. Armstrong, L.R. Pederson, J. Li, C.A. Lewinsohn,aran, Solid State Ionics 113115 (1998) 571583.

tevenson, K. Hasinska, N.L. Canfield, T.R. Armstrong, J. Elec-. Soc. 147 (9) (2000) 32133218.

evenson, T.R. Armstrong, D.E. McCready, L.R. Pederson, W.J.J. Electrochem. Soc. 144 (10) (1997) 36133620.ley, P.R. Slater, T. Ishihara, J.T.S. Irvine, Electrochemical Societydings, 2003-07, SOFC VII, 2003, pp. 315323.uki, K. Fujimoto, S. Ito, Solid State Ionics, in press.umada, H. Hara, F. Munakata, E. Iguchi, Solid State Ionics 176245251.hews, N. Rabu, J.R. Sellar, B.C. Muddle, Solid State Ionics 128111115.i, H. Zhang, B. Bergman, X. Zou, J. Eur. Ceram. Soc. 26 (2006)364.N. Liu, Y. Xu, Y. Yuan, P. Majewski, F. Aldinger, J. Alloys Compd.,

s.Q. He, L. Pei, Y. Ji, J. Liu, J. Am. Ceram. Soc. 89 (8) (2006)667.horkounov, H. Nafe, F. Aldinger, J. Solid State Electrochem. 10479487.babu, S. Ghosh, W. Zhao, H. Jena, J. Power Sources, in press.ara, S. Ishikawa, M. Ando, H. Nishguchi, Y. Takiga, Solid State

173 (2004) 915.ara, J. Tabuchi, S. Ishikawa, J. Yan, M. Enoki, H. Matsumoto,tate Ionics, in press.ki, J. Yan, H. Matsumoto, T. Ishihara, Solid State Ionics, in press.ara, Y. Tsurata, Y. Chunying, T. Todaka, H. Nishiguchi, Y. Takita,rochem. Soc. 150 (1) (2003) E17E23.ara, M. Ando, M. Enoki, Y. Takita, J. Alloys Compd. 408412507511.ara, S. Ishikawa, C. Yu, T. Akbay, K. Hosoi, H. Nishiguchi, Y.Phys. Chem. Chem. Phys. 5 (2003) 22572263.aki, F. Nishiwaki, J. Kanou, S. Yamasaki, K. Hosoi, T. Miyazawa,mada, N. Komada, J. Alloys Compd. 408412 (2006) 512

ada, N. Chitose, J. Akikusa, N. Murakami, T. Akbay, T. Miyazawa,chi, A. Hasegawa, M. Yamada, K. Hoshino, K. Hosoi, N. Komada,

CF

[210] TIo

[211] PA

[212] X2

[213] KS

[214] WM

[215] W1

[216] AJ.

[217] GS

[218] TS

[219] CMS

[220] RZV

[221] InFp

[222] A(2

[223] NSA

[224] CF

[225] Z(2

[226] M3

[227] K(2

[228] YS

[229] M[230] T

S[231] P

3[232] X

1[233] T

(2[234] T[235] E

P[236] H

1[237] E

2[238] Y

2[239] F

T3rev, A.V. Kovalevsky, A.L. Shaula, M.V. Patrakeev, J.R. Frade,Marques, Solid State Ionics 177 (2006) 549558.ara, S. Ishikawa, K. Hosoi, H. Nishiguchi, T. Takitsa, Solid State

175 (2004) 319322.z-Coll, J.R. Nunez, Frade, J. Electrochem. Soc. 153 (3) (2006)A483.g, J. Duquette, A. Petric, Electrochemical Society Proceedings,7, SOFC IX, 2005, pp. 10021007.ng, M. Feng, J.B. Goodenough, M. Schmerling, J. Electrochem.3 (11) (1996) 36303636.hen, H.W. Nie, W.H. Huang, R. Zheng, H.Y. Tu, T.-L. Wen, J.

Sci. Lett. 22 (9) (2003) 651653.n, T. Wen, H. Nie, R. Zheng, Mater. Res. Bull. 38 (8) (2003)328.umidis, A. Ahmad-Khanlou, Z. Samardzija, D. Kolar, Fresenius. Chem. 365 (13) (1999) 277281.ostogloudis, C. Ftikos, A. Ahmad-Khanlou, A. Naoumidis, D.Solid State Ionics 134 (12) (2000) 127138.ta, K. Yamaji, N. Sakai, H. Yokokawa, A. Weber, E. Ivers-Tiffee,tate Ionics 133 (34) (2000) 143152.irusis, M. Kilo, P. Fielitz, G. Borchardt, U. Guntow, A. Weber, A., E. Ivers-Tiffee, Electrochemical Society Proceedings, 2001-16,VII, 2001, pp. 914921.ric, S. Ohara, K. Mukai, T. Fukui, H. Yoshida, T. Inagaki, X.K. Miura, Electrochemical Society Proceedings, 1999-19, SOFC9, pp. 938944.

i, H. Yoshida, K. Miura, S. Ohara, R. Maric, X. Zhang, K. Mukai, T.Electrochemical Society Proceedings, 2001-16, SOFC VII, 2001,972.

haula, V.V. Kharton, F.M.B. Marques, J. Eur. Ceram. Soc. 24 (9)26312639.ai, T. Horita, K. Yamaji, M.E. Brito, H. Yokokawa, A. Kawakami,uoka, N. Watanabe, A. Ueno, J. Electrochem. Soc. 153 (3) (2006)

A625.unnings, S.J. Skinner, G. Amow, P.S. Whitfield, I.J. Davidson, J.

ell Sci. Technol. 2 (2005) 3437.. Cheng, Y. Dong, H. Wu, Y. She, B. Yi, Solid State Ionics 176

655661.vat, A. Ahmad-Khanlou, Z. Samardzija, J. Holc, Mater. Res. Bull.13) (1999) 20272034.ng, J.-H. Wan, J.B. Goodenough, J. Electrochem. Soc. 148 (7)A788A794.N.M. Sammes, Electrochemical Society Proceedings, 2005-07,

IX, 2005, pp. 11271136.itani, M. Matsuda, M. Miyake, Solid State Ionics, in press.hen, K.-Z. Fung, Electrochemical Society Proceedings, 2003-07,VII, 2003, pp. 339348.an, W. Yan, Y. Lizhai, M. Zongqiang, Solid State Ionics 177 (2006)3.u, Q.-Z. Yan, Y.-H. Ma, W.-F. Zhang, C.-C. Ge, Solid State Ionics06) 10411045.

ayashi, H. Watanabe, M. Hibino, T. Yao, Solid State Ionics 17624392443.ber, Solid State Ionics 162163 (2003) 277281.

bova, B.V. Zhuravlev, A.K. Demin, S.Q. Song, P.E. Tsiakaras, J.Sources 157 (2006) 720723.rparvar, J.A. Kilner, R.T. Baker, M. Sahibzada, Solid State Ionics3 (2003) 297303.

drick, M.S. Islam, P. Slater, Electrochemical Society Proceedings,7, SOFC IX, 2005, pp. 11421148.ng, S.H. Chan, K.A. Khor, Electrochemical Society Proceedings,7, SOFC IX, 2005, pp. 11101116.k, I. Abrahams, W. Wrobel, S.C.M. Chan, A. Kozanecka,owski, J.R. Dygas, Solid State Ionics 175 (2004) 335

40 J.W. Fergus / Journal of Power Sources 162 (2006) 3040

[240] A.A. Taremchenko, A.L. Shaula, V.V. Kharton, J.C. Waerenborgh, D.P.Rojas, M.V. Patrakeev, F.M.B. Marques, Solid State Ionics 171 (2004)5159.

[241] H. Yoshioka, S. Tanase, Solid State Ionics 176 (2005) 23952398.[242] A.L. Shaula, V.V. Kharton, F.M.B. Marques, Solid State Ionics, in press.[243] S. Georges, F. Gouteniore, F. Altorfer, D. Sheptyakov, F. Fauth, E. Suard,

P. Lacorre, Solid State Ionics 161 (2003) 231241.

[244] K.S. Yoo, A.J. Jacobson, J. Mater. Sci. 40 (2005) 44314434.

[245] M. Kumar, I.A. Raj, R. Pattabirman, Ionics 10 (56) (2004) 429435.

[246] J.-D. Wang, Y.-H. Xie, Z.-F. Zhang, R.-Q. Liu, Z.-J. Li, Mater. Res. Bull.40 (2005) 12941302.

Electrolytes for solid oxide fuel cellsIntroductionStabilized zirconiaDoped ceriaStrontium/magnesium-doped lanthanum gallateOther electrolytesConclusionsReferences