Application of E h -pH diagram for room temperature precipitation of zinc stannate microcubes in an aqueous media

Materials Research Bulletin 49 (2014) 645–650

Application of Eh-pH diagram for room temperature precipitation ofzinc stannate microcubes in an aqueous media

Ashraf T. Al-Hinai a,*, Muna H. Al-Hinai a,b, Joydeep Dutta b

a Department of Chemistry, College of Science, Sultan Qaboos University, 123, Alkhoud, Omanb Water Research Center, Sultan Qaboos University, 123, Alkhoud, Oman

A R T I C L E I N F O

Article history:

Received 7 July 2013

Received in revised form 17 September 2013

Accepted 6 October 2013

Available online 15 October 2013

Keywords:

B. Chemical synthesis

C. X-ray diffraction

C. Electron microscope

C. Thermogravimetric analysis

D. Microstructure

A B S T R A C T

Potential-pH diagram assisted-design for controlled precipitation is an attractive method to obtain

engineered binary and ternary oxide particles. Aqueous synthesis conditions of zinc stannate (ZnSnO3)

particles at low temperature were formulated with the assistance of potential-pH diagram. The pH of a

solution containing stoichiometric amounts of Zn2+ and Sn4+ was controlled for the precipitation in a one

pot synthesis step at room temperature (25 8C). The effect of the concentration of the reactants on the

particle size was studied by varying the concentration of the precursor (Zn2+ + Sn4+) solution. Scanning

electron micrographs show that the particles are monodispersed micron sized cubes formed by the self-

organization of nano-sized crystallites. The obtained microcubes characterized by X-ray Diffraction and

thermo gravimetric analysis (TGA) show that the particles are in ZnSnO3�3H2O form.

� 2013 Elsevier Ltd. All rights reserved.

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jo u rn al h om ep age: ww w.els evier .c o m/lo c ate /mat res b u

1. Introduction

Studies have been made for the synthesis of a variety of binarymetal oxide materials like titanium dioxide (TiO2) [1,2], hematite(Fe2O3) [3], zinc oxide ZnO [4,5] etc., which have been reviewedextensively in the literature. Binary semiconducting metal oxideshave received renewed attention in the last decade due to theirunique properties rendering them suitable for a wide range ofapplications [6–8] as catalysts, and in optoelectronic devicesincluding lasers, diodes, and gas sensors, amongst others [9]. Thedrawback of binary oxides is generally their instability under widepH variations. The binary oxide particles can be precipitated undermild conditions. Physical and chemical properties of ternary oxidescan be more easily tailored than the binary oxides by changing thecomposition of the three different components [10]. It is generallyagreed that ternary oxides would allow better flexibility to designnew materials for a desired application [11]. However due to thepresence of two oxide phases, wet chemical synthesis of ternaryoxides get difficult. Theoretical understanding of the precipitationreaction would lead to designing engineered materials includingternary metal oxides under controlled conditions. Therefore,controlled size and shape of the material can be engineered by aproper understanding of the precipitation conditions.

* Corresponding author. Tel.: +968 214141473; fax: +968 24141469.

E-mail addresses: [email protected] (A.T. Al-Hinai), [email protected]

(J. Dutta).

0025-5408/$ – see front matter � 2013 Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.materresbull.2013.10.011

Zinc stannate or zinc tin oxide (ZTO) is a ternary oxide formedby the combination of zinc oxide (ZnO) and tin dioxide (SnO2). It isa wide band gap (3.35–3.89 eV) n-type semiconductor [12], havingtwo dominant crystalline phases: cubic spinel (Zn2SnO4) andtrigonal ilmenite (ZnSnO3) [13]. ZTO is often used for fabricatingscratch resistant films and is robust to several chemical etchants.Further, zinc stannate shows improved stability in adverse pHconditions where the binary oxides are not that much stable [14].Owing to the chemical stability, zinc stannate (ZnSnO3) has foundapplications in gas sensors [15–20], photocatalysis [21], asphotoconductors [22], in lithium ion batteries and in dye-sensitized solar cells as well as a fire retardant. Zinc stannateand zinc hydroxy stannate (ZnSnO3 and ZnSnO3�3H2O) help lowersmoke formation in the presence of halogenated flame retardantsystems [23].

Synthesis of zinc stannate micro-/nanostructures have beenreported in the literature, including, microcubes [19,24], micro-spheres [25], microwires/microrods [26], and faceted crystals [27]etc. Solid state reactions between ZnO and SnO2 have beensuccessfully used to form ZnSnO3(s); however above 700 8C,ZnSnO3(s) transforms to the more stable ZnSn2O4 phase [15].Another common method of synthesis of ZnSnO3 involve theprecipitation of a precursor from an acidic solution of Zn2+(aq) andSn4+(aq) ions by gradually adding a base [28]. The precursor isgenerally treated at high temperatures in an autoclave at about200 8C to obtain the metastable ZnSnO3(s) [9,29]. High tempera-ture synthesis of the material leads to the formation ofpolydispersed particles with a high probability for the formation

14121086420

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

pH

Eh

(V)

H2O Lim it

Sn

Sn(OH)4

Sn4+

Sn2+

Sn(OH)62-

Fig. 1. Pourbaix diagram of Sn-H2O system at 25 8C.

A.T. Al-Hinai et al. / Materials Research Bulletin 49 (2014) 645–650646

of mixed phases. Thus, low temperature synthesis is preferable forthe synthesis of monodispersed phases of zinc stannate.

Potential-pH diagram shows possible stable phases of anelectrochemical system in equilibrium that is popularly known asPourbaix diagram. In a Pourbaix diagram, the vertical axis is thepotential normally with respect to the standard hydrogenelectrode (SHE) and the horizontal axis is pH (=�log aH+), whereaH+ is the activity of proton [30]. The diagram can be used to designthe synthesis of the material by controlling the potential and pHconditions at the thermodynamic stability area of the material. In arecent work, aqueous stability of binary compounds of Mn, Zn, Ti,Ta and N has been examined [31]. Persson et al. predicted theformation of binary compounds by calculating the Gibbs freeenergy of the compound in aqueous environment and applied theircalculations to study the stability of some photocatalysts inaqueous media. Zinc Pourbaix diagram was also calculated in thatwork using thermodynamic data available and compared withthermodynamic data estimated using Density Functional Theorycalculations [31]. The stability area of the ternary zinc tin oxide(ZnSnO3) was not located in Zn-H2O Pourbaix diagram, sincethermodynamic data of ZnSnO3 was not available. In this work,ZnSnO3 stability area was estimated to be the areas where bothZnO and SnO2 are stable in aqueous media at the same pH and Eh

conditions whereby stability area of ZnSnO3 was located in amodified Zn-Sn-H2O Pourbaix diagram. By understanding thethermodynamic stability area of ZnSnO3, an one pot precipitationprocess for the synthesis of zinc stannate microcubes at roomtemperature was obtained with the assistance of Pourbaixdiagrams. The synthesis process then was used to study the effectof reactant concentrations on the size and shape of ZnSnO3

particles.

2. Experimental

2.1. Construction of Sn-Zn-H2O Pourbaix diagram

Pourbaix diagram of Zn-H2O and Sn-H2O were obtained usingHSC 5.1 program (Outokumpu, Finland) [33]. These two diagramswere used to analyze the thermodynamically stable species of thetwo metals at different pH conditions. The stability area of ZnSnO3

was estimated from the stability area of the ZnO and SnO2 andconfirmed by experiments. A precursor solution of Sn4+, Zn2+ inSodium hydroxide solution was titrated with hydrochloric acid andthe pH at which the precipitation started was monitored. Theobtained precipitate was collected and identified by X-raydiffraction. Then, the precipitation pH was used to calculate theGibbs free energy for the formation of ZnSnO3. The three limits ofZnSnO3 stability were obtained and overlapped on Sn-H2OPourbaix diagram.

2.2. Synthesis of ZnSnO3

All the reagents used in this work were analytical grade andwere used without further purification. Tin(IV) chloride pentahy-derate (97.5%), zinc chloride (97%), manganese(II) chloride (98%)and sodium hydroxide were supplied by BDH Chemicals. For thepreparation of (0.01 M Zn2+ + 0.01 M Sn4+) alkaline solution, zincchloride (6.8145 g, 0.050 mol) and tin(IV) chloride (17.5293 g,0.050 mol) were dissolved in 37% HCl(aq) (98 mL) producing aclear solution after 2 h of ultrasonication. The Zn2+/Sn4+ solutionwas further diluted to 100.0 mL with 37% HCl(aq) to achieve 0.5 Mconcentration of each metal in the solution. After 24 h, precipita-tion was observed and the precipitate was dissolved by adding(3.0078 g, 0.167 mol) of distilled water and then the solutionwas stirred for 270 min, a clear solution was obtained with0.485 M concentration of Zn2+(aq) and Sn4+(aq). 10.31 mL of the

0.485 M Zn2+/Sn4+ solution was then added with micropipettein 0.500 mL aliquots to 2.7 M NaOH(aq) (412 mL) under continu-ous stirring, yielding a colorless solution. Then, the solution wasdiluted to 500.0 mL with distilled water. A colorless solution wasproduced with 0.01 M of each metal (Zn2+ and Sn4+). 100.0 mL ofthe (0.01 M Zn2+ + 0.01 M Sn4+) in NaOH(aq) solution was stirred atroom temperature (25 8C), followed by the addition of 10.2 MHCl(aq) (18.2 mL) dropwise using a peristaltic pump undercontinuous stirring, producing a white precipitate. The pH of thewhite mixture was adjusted to 10.82 with 10.2 M HCl(aq) whichwas added slowly with a dropper. Then the white precipitate wasaged at room temperature for two days and thereafter it wascollected by centrifugation at 3200 rpm for 10 min. The obtainedwhite precipitate was washed three times with distilled water andonce with acetone. This white precipitate was then kept in oven at80 8C overnight. Similar synthesis process was repeated using(0.006 M Zn2+ + 0.006 M Sn4+) and (0.003 M Zn2+ + 0.003 M Sn4+)solutions.

2.3. Characterization of ZnSnO3 samples

The XRD patterns of the produced powder was collected using XPert PRO X-Ray Diffraction System which was operated at 45 kVand 40 mA using Cu-Ka radiation (l = 1.54060 A). The range of 2u8of the obtained patterns was from 208 to 708 in 0.028/s steps. Thecrystallite size was estimated from the broadening of the XRDspectra using Debye–Scherrer equation and the full width at halfmaximum of the XRD peak was calculated using FullProf Suite [32].

Scanning Electron Micrograph (SEM) were obtained by using aJEOL JSM-5600 LV Scanning Electron Microscope operating at20 kV; a double sided carbon-adhesive stub was used as a sampleholder, and the sample was coated with gold using a sputter coaterprior to the observations.

3. Results and discussion

3.1. Construction of Sn-Zn-H2O Pourbaix diagram

Pourbaix diagram is a plot of the equilibrium potential (Eh)between a metal and its various oxidized species as a function ofpH. As potential-pH Diagrams are derived entirely from thermo-dynamics, the diagram can be used to determine which species isthermodynamically more stable at a given potential (Eh) and pH[30]. Pourbaix diagrams of Sn-H2O system (Fig. 1) [33] and Zn-H2Osystem (Fig. 2) [33] were used to design the synthesis route ofZnSnO3 at low temperature by controlling the pH of Zn2+ and Sn4+

aqueous solution. In aqueous medium, tin(VI) hydroxide (Sn(OH)4)is stable in a wide pH range (�0–13). On the other hand, zinc

14121086420

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

pH

Eh

(V)

H2O Limit

Zn

Zn(OH)2

Zn2+

ZnO22-

Fig. 2. Pourbaix diagram of Zn-H2O system at 25 8C.

Fig. 3. (a) X-ray diffraction patterns of ZnSnO3 from JCPDS (11-0274) and (b) ZnSnO3

precipitated at 25 8C.

A.T. Al-Hinai et al. / Materials Research Bulletin 49 (2014) 645–650 647

hydroxide (Zn(OH)2) is stable only in the pH range 7–13. As can beobserved from the Pourbaix diagrams shown in Figs. 1 and 2, theprecipitation of tin oxide SnO2(s) or tin hydroxide Sn(OH)4 starts ata very low pH, while ZnO(s) or the hydroxide form Zn(OH)2

requires a much higher pH to precipitate from an aqueous solution.This suggests that upon the gradual increase in pH of a(Zn2+(aq) + Sn4+(aq)) acid mixture, it would precipitate out tinoxide SnO2(s) or tin hydroxide Sn(OH)4 consuming nearly all thetin species, and by the time the pH is high enough to precipitate thezinc ions, almost negligible amounts of Sn4+(aq) ions would still bepresent in the solution to contribute to the formation of ternaryoxide phases. The chemical equations are given in (1)–(4)

Sn4þðaqÞ þ 4OH�ðaqÞ ! SnðOHÞ4ðsÞ (1)

SnðOHÞ4ðsÞ ! SnO2ðsÞ þ 2H2OðlÞ (2)

Zn2þðaqÞ þ 2OH�ðaqÞ ! ZnðOHÞ2ðsÞ (3)

ZnðOHÞ2ðsÞ ! ZnOðsÞ þ H2OðlÞ (4)

In order to obtain ZnSnO3, the two solid precipitates of Zn andSn should react, as any of the two equations given below [5] whichis usually achieved at higher temperature [15]

ZnðOHÞ2ðsÞ þ SnðOHÞ4ðsÞ ! ZnSnO3ðsÞ þ 3H2OðlÞor ZnOðsÞ þ SnO2ðsÞ ! ZnSnO3ðsÞ (5)

As can be observed from the aqueous stability diagrams given inFigs. 1 and 2, both tin and zinc metals are soluble above pH 13forming Sn(OH)6

2�(aq) and ZnO22�(aq), respectively. The region of

stability of the mixed oxides usually occurs at higher pH than itsindividual components as observed in similar systems. To ourknowledge, thermodynamic data for the formation of ZnSnO3 isnot available, so the exact region of its stability cannot beascertained. However, by comparing it to other known systems likeferrites [34] and titanates [35], it should be on the higher pH range,closer to the region of stability of Sn(OH)6

2�(aq) and ZnO22�(aq).

Based on this assumption, the precipitation of tin oxide orhydroxides could be avoided by starting from a high pH (basicregion) and then lowering the pH gradually. As the pH is dropped,Zn(OH)2 is formed below pH 13. This species is a gelatinous solidwhich react with Sn(OH)6

2�(aq) species forming ZnSnO3(s), thusgoing from the region of stability of Sn(OH)6

2�(aq) and ZnO22�(aq)

into the expected region of the formation of ZnSnO3(s) by avoiding

the region of the formation of SnOH2(s) according to Eq. (6)

SnðOHÞ62�ðaqÞ þ ZnðOHÞ2ðsÞ þ 2HþðaqÞ fi ZnSnO3ðsÞ þ H2OðlÞ(6)

The precipitates obtained by following the above explainedscheme were dried and then the phases were identified by X-raydiffraction (XRD). The XRD pattern of the prepared ZnSnO3

particles (Fig. 3) indexed to standard ZnSnO3 in JCPDS (11-0274)[25] shows that single phase ZnSnO3 was obtained and no otherphases could be detected. The stability area of ZnSnO3 formationwas confirmed by calculating the thermodynamic data of ZnSnO3.A precipitation titration was used to monitor the pH at whichZnSnO3 begins to precipitate starting from an alkaline (Zn2+ + Sn4+)solution (the pH value is dependent on the starting precursorsolution concentration). It was observed that ZnSnO3 begins toprecipitate at pH 12.6 when the (0.01 M Zn2+ + 0.01 M Sn4+)alkaline solution was used. This pH represent the equilibriumbetween ZnSnO3 and the reactant species Zn(OH)2 and Sn(OH)6

2�

and the equilibrium constant was calculated using Eq. (6):[Sn(OH)6

2�] = [ZnO22�] = 0.01 M and pH 12.6. The Gibbs free

energy of the reaction was calculated as in Eq. (7), then it wasused to calculate the Gibbs free energy of formation of ZnSnO3(s)(DG

�f ðZnSnO3ðsÞÞ ¼ �822:95 kJ mol�1)

DG0 ¼ �RT ln K ¼ �155:208 kJ mol�1 (7)

The precipitation of ZnSnO3 from Zn(OH)2(s) and Sn(OH)62�(aq)

is pH dependent process and it is presented as a vertical line inPourbaix diagram. This line was obtained from the followingequation,

pH ¼ 1

2½log K þ log½SnðOHÞ6

2��� (8)

At low pH, ZnSnO3 dissolves to yield Sn(OH)4(s) and Zn2+(aq)following the equation given below.

ZnSnO3ðsÞ þ 2HþðaqÞ þ H2OðlÞ fi Zn2þðaqÞ þ SnðOHÞ4ðsÞ (9)

The Gibbs free energy of the dissolution reaction was calculatedfrom the Gibbs free energy of the formation of the species in thereaction and it was �40.271 kJ mol�1. The relation between pH ofthe dissolution of ZnSnO3 and the concentration of Zn2+(aq) in theprecursor solution is,

pH ¼ 1

2ðlog K � log½Zn2þ�Þ (10)

The dissolution of ZnSnO3 at pH lower than pH 4 was concludedby carrying out the precipitation experiment at low pH. A samplewas prepared at room temperature starting with (0.5 M

A.T. Al-Hinai et al. / Materials Research Bulletin 49 (2014) 645–650648

Zn2+ + 0.5 M Sn4+) acidic solution and adding a base till pH � 10,producing SnO2 as expected from Pourbaix diagram of Zn-H2O andSn-H2O system. Similar results were obtained by starting theprecipitation at alkaline medium and dropping the pH below pH 4where Zn is in Zn2+(aq) form and tin in the Sn(OH)4 or SnO2(s)forms. The XRD of the sample prepared at these conditions isshown in the supplementary information (Figure S1) whichconfirms the presence of SnO2 as matched to JCPDS (41-1445) [36].

Eqs. (8) and (10) describe the pH dependent process for theformation of ZnSnO3 beginning at high pH and its subsequentdissolution at low pH. These two processes are pH limits forZnSnO3 precipitation at constant potential and they are presentedas a vertical line in Pourbaix diagram. The potential-pH limit of thestability of ZnSnO3 was estimated from the reduction of ZnSnO3

into two regions namely the reduction of ZnSnO3 into Zn(OH)2(s)and Sn(s) between pH 7 and 12.6 and the reduction of ZnSnO3 intoZn2+(aq) and Sn(s) in the pH range 4.5–7. The reverse of the firstreduction step between pH 6 and 12.6 is the formation of ZnSnO3

by the oxidation of Zn(OH)2(s) and Sn(s) in aqueous media asfollows

ZnðOHÞ2ðsÞ þ SnðsÞ þ H2OðlÞ fi ZnSnO3ðsÞ þ 4HþðaqÞ þ 4e�

(11)

The Gibbs free energy of the above reaction was calculated to be�31.87 kJ mol�1.

The formation of ZnSnO3 from the Zn(OH)2(s) and Sn(s)(Eq. (11)) shown as a diagonal line in Pourbaix diagram wasestimated from the following equation:

pe ¼1

4log K � pH (12)

where pe = (Eh/0.0591). A plot of Eh versus pH in Eq. (12) is linearwith negative slope.

The second reduction step between pH 4.5 and 7 is thereduction of ZnSnO3 into tin metal and Zn2+(aq) following the

Fig. 4. Pourbaix diagram of Zn-Sn-H2O system at 25 8

equation below

ZnSnO3ðsÞ þ 6HþðaqÞ þ 4e� fi SnðsÞ þ Zn2þðaqÞ þ 3H2OðlÞ(13)

The Gibbs free energy of the formation of ZnSnO3(s), H2O(l) andZn2+(aq) were used to calculate the Gibbs free energy of the abovereaction and it was �35.79 kJ mol�1. This reaction is presented as adiagonal line in Pourbaix diagram and generalized by the followingequation,

pe¼ ð1=4Þlog K � ð3=2ÞpH � ð1=4Þlog½Zn2þ� (14)

After the determination of the three ZnSnO3 stability limiting(Eh-pH) lines, these lines were overlapped on a Sn-H2O Pourbaixdiagram that was modified to obtain a Pourbaix diagram of Sn-Zn-H2O system (Fig. 4). The modified diagram shows the stability areaof ZnSnO3 that can be used to control the pH and potentialconditions for the precipitation of ZnSnO3 at room temperature.

3.2. Characterization of the prepared ZnSnO3

To study the effect of the precursor concentration on theparticle morphology, ZnSnO3 was prepared with varying concen-trations of (Zn2+ + Sn4+) in alkaline solution by keeping equimolarratio of zinc and tin ([Zn2+]/[Sn4+] 1:1). Three concentrations of theequimolar precursor solution were considered, 0.01, 0.006 and0.003 M. The scanning electron micrographs (SEM) of the obtainedprecipitates are shown in Fig. 5. Monodispersed uniform cubeswith micron sized particles were obtained for all the threeconcentrations considered here. It can be observed that bychanging the precursor concentration, the size of the obtainedparticles can be varied. The average size of the obtained particleswere 1.4, 0.700 and 1.1 micron synthesized using (0.01 MZn2+ + 0.01 M Sn4+), (0.006 M Zn2+ + 0.006 M Sn4+) and (0.003 MZn2+ + 0.003 M Sn4+) alkaline precursor solutions respectively.Smaller particles were observed at the surface of the micron sizedparticles, indicating that the particles are polycrystalline and self-organized from tiny crystallites.

C for 0.01 molar concentration of Zn2+ and Sn4+.

Fig. 5. Scanning Electron micrograph of ZnSnO3 prepared at 25 8C using equimolar concentration of zinc and tin ions (Zn2+) and (Sn4+) (a) 0.01 M, (b) 0.006 M and (c) 0.003 M.

Fig. 6. X-ray diffraction pattern of ZnSnO3 prepared at room temperature with

varying concentration of equimolar (Zn2+) & (Sn4+) solution: (a) 0.01 M, (b) 0.006 M,

(c) 0.003 M.

Fig. 7. FTIR spectrum of ZnSnO3 sample prepared at room temperature using

equimolar concentration of (Zn2+) and (Sn4+) (a) 0.003 M, (b) 0.006 M and (c)

0.01 M.

A.T. Al-Hinai et al. / Materials Research Bulletin 49 (2014) 645–650 649

The XRD patterns of the samples illustrated in Fig. 6 wereindexed to ZnSnO3 in JCPDS (11-0274) with no additional phasesobserved. Table 1 shows the crystallite sizes which are in thenanometric scale and estimated from XRD spectra. The crystallitesize was found to decrease from �44 to 32 nm with increasingprecursor concentration from 0.003 M Zn2+ to 0.006 M Zn4+.

The FTIR spectra of samples were determined and compared toFTIR of ZnSnO3 from the literature. The FTIR spectra of the threeZnSnO3 samples are shown in Fig. 7. It was observed that the infra-red spectra of the samples prepared in this work is closer to that ofzinc hydroxystannate (ZnSn(OH)6, ZHS) and slightly different fromthe infra-red absorption spectra of ZnSnO3 found in the literature[37]. The broad peak at 3276 cm�1 is assigned to OH groupstretching vibration from water molecules and the peak at1640 cm�1 is the OH binding band. The H-bonding between watermolecules is observed in the FTIR spectra as a small band at800 cm�1. Sn–O stretching peak was detected at 540 cm�1. Thepresence of the OH band is attributed to the water molecules on thesurface of ZnSnO3 particles, indicating that the prepared ZnSnO3 isin its hydrated form. These water molecules were not removed

Table 1Crystallite size calculated from the band broadening of X-ray diffraction pattern

(1 1 1 peak) of ZnSnO3 prepared with different Zn2+ and Sn4+ concentrations.

[Zn2+] and [Sn4+]

(mol/L) (each)

Peak position

(2u8)FWHM

(8)D

(nm)

0.01 23.097513 0.246699 32.88290

0.006 23.00171 0.251009 32.31278

0.003 22.97726 0.186319 43.5299

during the drying step at 80 8C. Thermo gravimetric analysis wasperformed on the ZnSnO3 sample which was prepared using(0.006 M Zn2+ + 0.006 M Sn4+) precursor solution at 25 8C. The TGAcurve (Supplementary Information, Figure S2) shows a 20% weightloss at the temperature range 20–400 8C. The 20% weight loss thuscould be attributed to the removal of three water molecules fromthe zinc stannate sample. Therefore the synthesized particles are(ZnSnO3�3H2O).

4. Conclusion

The synthesis route for obtaining zinc tin oxide compound wasdesigned with the assistance of Pourbaix diagram of Zn-H2O andSn-H2O systems at 25 8C. ZnSnO3 particles were precipitatedsuccessfully in an one pot reaction at room temperature bycontrolling the pH of Zn2+, Sn4+ alkaline solution. The region ofstability of ZnSnO3 estimated to be in the range of pH 8–12 wasconfirmed by studying the effect of pH for ZnSnO3 precipitationand dissolution. A white powder was found to be pure ZnSnO3 andindexed to JCPDS card (11-0274). Cubic monodispersed ZnSnO3

particles were obtained at room temperature with an average sizeof 700 nm using (0.006 M Zn2+ + 0.006 M Sn4+) precursor solution.Two other concentrations produced 1.4 and 1.1 micron particlesfor the 10 mM and 3 mM solutions respectively. The crystallite sizewas calculated from the broadening in the XRD spectra usingScherer equation. Crystallite size was in the nano scale and wasfound to reduce with increasing precursor concentration. Poten-tial-pH diagram assisted-design for controlled precipitation is an

A.T. Al-Hinai et al. / Materials Research Bulletin 49 (2014) 645–650650

attractive method to obtain engineered binary and ternary oxideparticles.

Acknowledgements

This work was partially supported by Department of Chemistryat College of Science and the TRC Chair in Nanotechnology SultanQaboos University, Oman. The authors thank Mr. Saif Al-Mamariand Mrs. Sameera Al-Kharusi from Department of Earth Science fortheir help in the XRD analysis. Authors express their thanks to Dr.Issa Al-Amri and Mr. Mohammed Al-Kindi from College ofMedicine for assistance in the SEM analysis.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.materres-bull.2013.10.011.

References

[1] S. Cassaignon, M. Koelsch, J.-P. Jolivet, J. Phys. Chem. Solids 68 (2007) 695.[2] G. Cao, Q. Zhang, D. Liu, J. Xi, G. Cao, 3rd International Photonics & OptoElectronics

Meetings (POEM 2010), IOP, vol. 276, 2011.[3] E. Montiel-Palacios, A.K. Medina-Mendoza, A. Sampieri, C. Angeles-Chavez, I.

Hernandez-Perez, J. Ceram. Process. Res. 10 (2009) 548.[4] S. Baruah, C. Thanachayanont, J. Dutta, Sci. Technol. Adv. Mater. 9 (2008) 1.[5] Y. Liao, C. Xie, Y. Liu, H. Chen, H. Li, J. Wu, Ceram. Int. 38 (6) (2012) 4437.[6] M.A. Carpenter, S. Mathur, A. Kolmakov (Eds.), Metal Oxide Nanomaterials for

Chemical Sensors, Springer, 2013.[7] L. Chmielarz, P. Kustrowski, A. Rafalska-Łasocha, R. Dziembaj, Appl. Catal., B 58

(2005) 235.

[8] M.A. Carreon, V.V. Guliants, Catal. Today 99 (2005) 137.[9] S. Baruah, J. Dutta, Sci. Technol. Adv. Mater. 12 (2011) 1.

[10] B. Tan, E. Toman, Y. Li, Y. Wu, J. Am. Chem. Soc. 129 (2007) 4162.[11] Z. Li, Y. Zhou, C. Bao, G. Xue, J. Zhang, J. Liu, T. Yu, Z. Zou, Nanoscale 4 (11) (2012)

3490.[12] M.K. Jayaraja, K.J. Saji, K. Nomura, T. Kamiya, H. Hosono, Am. Vac. Soc. 26 (2008)

495.[13] M. Miyauchi, Z. Liu, Z.-G. Zhao, S. Anandan, K. Hara, Chem. Commun. 46 (2010)

1529.[14] Y. Zhang, M. Guo, M. Zhang, C. Yang, T. Ma, X. Wang, J. Cryst. Growth 308 (2007)

99.[15] Y. Cao, D. Jia, J. Zhou, Y. Sun, Chem. Commun. 2009 (2009) 4105.[16] P. Song, Q. Wang, Z. Yang, Mater. Lett. 65 (2011) 430.[17] P. Song, Q. Wang, Z. Yang, Sens. Actuators B 156 (2011) 983.[18] X.Y. Xue, Y.J. Chen, Y.G. Wang, T.H. Wang, Appl. Phys. Lett. 86 (2005) 233101.[19] Y. Zeng, T. Zhang, H. Fan, G. Lu, M. Kang, Sens. Actuators B 143 (2009) 449.[20] Y. Zeng, K. Zhang, X. Wang, Y. Sui, B. Zou, W. Zheng, G. Zou, Sens. Actuators B 159

(2011) 245.[21] C. Fang, B. Geng, J. Liu, F. Zhan, Chem. Commun. (2009) 2350.[22] G. Shen, D. Chen, Recent Pat. Nanotechnol. 4 (2010) 20.[23] A.B. Morgan, J.W. Gilman, Fire Mater. 37 (2013) 259–279.[24] Y. Zeng, T. Zhang, H. Fan, W. Fu, G. Lu, Y. Sui, H. Yang, J. Phys. Chem. C 113 (2009)

19000.[25] G. Ma, R. Zou, L. Jiang, Z. Zhang, Y. Xue, L. Yu, G. Song, W. Li, J. Hu, CrystEng-

Commun 14 (2012) 2172.[26] H. Men, P. Gao, B. Zhou, Y. Chen, C. Zhu, G. Xiao, L. Wang, M. Zhang, Chem.

Commun. 46 (2010) 7581.[27] A. Sivapunniyam, N. Wiromrat, M. Myint, J. Dutta, Sens. Actuators B 157 (2011)

232.[28] H. Fan, Y. Zeng, X. Xu, N. Lv, T. Zhang, Sens. Actuators B 153 (2011) 170.[29] J. Xu, X. Jia, X. Lou, J. Shen, Solid-State Electron 50 (2006) 504.[30] D.A. Jones, Principles and Prevention of Corrosion, second ed., Upper Saddle

River, Pearson Education, 1996.[31] K.A. Persson, B. Waldwick, P. Lazic, G. Ceder, Phys. Rev. B 85 (2012) 235438.[32] T. Roisnel and J.R. Carvajal, WinPloter 2011, France 2011.[33] A. Roine, Outokumpu HSC Chemistry for Windows, Finland, 2002.[34] M. Abe, Electrochim. Acta 45 (2000) 3337.[35] Z. Wu, M. Yoshimura, Bull. Korean Chem. Soc. 20 (1999) 869.[36] S. Ray, P.S. Gupta, G. Singh, J. Ovonic Res. 6 (2010) 23.[37] J. Huang, X. Xu, C. Gu, W. Wang, B. Geng, Y. Sun, J. Liu, Sens. Actuators B 171 (2012)

572.