1 New Trends in Solvothermal Crystal Growth Processes International Seminar on Material Synthesis and Processing (ISMSP-2008) Taipeh (TAIWAN), 26-27 march.

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New Trends in SolvothermalNew Trends in Solvothermal

Crystal Growth ProcessesCrystal Growth ProcessesInternational Seminar on Material Synthesis and ProcessingInternational Seminar on Material Synthesis and Processing

(ISMSP-2008)(ISMSP-2008)

Taipeh (TAIWAN), 26-27 march 2008

Professor Gérard DEMAZEAUEméritus Professor

Institut de Chimie de la Matière Condensée de BORDEAUX (ICMCB)Centre National de la Recherche Scientifique (CNRS)Université BORDEAUX 1 « Sciences et Technologie »

site de l’ENSCPB (National Engineer School of Chemistry and Physics)

Adress: 87 Avenue du Dr A. Schweitzer33608 PESSAC-Cedex (FRANCE)

e-mail: [email protected]: 33 5 40 00 27 10

International Hydrothermal Solvothermal Association ISHA

mailto:[email protected]



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New Trends in Solvothermal Crystal Growth Processes

I) Definition of solvothermal processes and Main scientific domains involved

II) Solvothermal Processes and the synthesis of novel Materials

III) Solvothermal Processes and Crystal growth

III-1)Macroscopic scale and Nano-scale

III-2)Crystal growth at the Macroscopic scale

III-2-1)General features characterizing the solvothermal growth of large single crystals.(Principle,History,

Main factors , Main Defects….)

III-2-2) Crystal growth of oxides and non-oxides

III-2-3) Crystal growth of oxides (α-quartz,quartz-like,Calcite,ZnO…)

III-2-4) How very High Pressures can be involved?

III-2-5) Solvothermal Crystal Growth of Nitrides

I) .

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III-3) Crystal Growth at the Nano-scale:

How Solvothermal Processes can be used for developing functional morphologies for nano-crystallites ?

Some examples : 1D morphology : ZnO, InAs,PtFe nanocrystallites.

IV) Conclusions:

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I)I) Definition of solvothermal processes and Main scientific Definition of solvothermal processes and Main scientific domains involveddomains involved


III) Solvothermal Processes and Crystal growth

III-1)Macroscopic scale and Nano-scale

III-2)Crystal growth at the Macoscopic scale

III-2-1)General features characterizing the solvothermal growth of large single crystal.(Principle,History, Main

factors , Main Defects….)

III-2-2) Crystal of oxides and non-oxides

III-2-3) Crystal growth of oxides (α-quartz,quartz-like,Calcite,ZnO…)

III-2-4) How High Pressures can be involved?

III-2-5) Solvothermal Crystal Growth of Nitrides

I) .

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SOLVOTHERMAL PROCESS

The term « SOLVOTHERMAL » was proposed at the beginning of the 90’s (G. DEMAZEAU et al.) during the development of non-aqueous solvents.

Examples.

Synthesis and crystal growth of nitrides using liquid ammonia (NH3) as solvent ammothermal process !

Synthesis and crystal growth of Fe3O4 as small single crystals using C2H5OH as solvent alcoholothermal process…!

Consequently each solvent can lead to a specific « word » for different processes characterized by the same features.

SOLVO – THERMAL

Solvent use of the temperature

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DEFINITION OF A SOLVOTHERMAL PROCESS

« Solvothermal process » is the generic term used for describing :

« a reaction between one (or several) precursor(s) in presence of a solvent (aqueous = hydrothermal or non aqueous) in a closed vessel at a temperature higher than the boiling temperature of this solvent »

Consequently high pressures are involved.

The system can be: in subcritical or in supercritical conditions of the solvent, homogeneous or heterogeneous.

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SOLVOTHERMAL PROCESSES

Solvothermal processes have been developed in different domains:

Synthesis of novel materials (new composition and new structure).If the synthesis is kinetically controled stabilization of metastable materials.Ex: Synthesis of layered oxides isostructural to natural phyllosilicates [P. REIG, G. DEMAZEAU, R. NASLAIN J. Mater. Sci. 32, 4189 (1997)]

Deposition of thin or thick films Ex: Ammothermal synthesis of thick Gallium nitride films employing acidic mineralizers D. EHRENTRAUT et al. J. Mater. Sci. (online)

Low-temperature sintering processes(N. YAMASAKI, K. YANAGISAWA ) Development of new processes for preparing functional materials Ex: Solvothermal synthesis of cubic boron nitride (c-BN).S. DONG et al. Mater. Lett. 58, 2791 (2004),X.P. HAO et al. J. Cryst. Growth 241, 124 (2002)

Solvothermal synthesis of diamond.S. KORABLOV, K.YOKOSAWA, D.KORABLOV, K.TOHJI, N.YAMASAKI Mater.Lett.60,3041(2006)

Solvothermal crystal growth

Preparation of nano-crystallites well defined in size and morphologyY.T.QUIAN,Y.L.GU,J.LU “The chemistry of nano-materials” Chap.7 (Eds.C.N.R. RAO et al.)

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I) Definition of solvothermal processes and Main involved Definition of solvothermal processes and Main involved scientific domains scientific domains


III) Solvothermal Processes and Crystal growthSolvothermal Processes and Crystal growthIV-1)Macroscopic scale and Nano-scaleIV-1)Macroscopic scale and Nano-scaleIV-2)Crystal growth at the Macoscopic scaleIV-2)Crystal growth at the Macoscopic scale

IV-2-1)General features characterizing the IV-2-1)General features characterizing the solvothermal growth of large single solvothermal growth of large single

crystal. crystal.(Principle,History,Main (Principle,History,Main factors,,Defects…) factors,,Defects…)

IV-2-2) Crystal of oxides and non-oxidesIV-2-2) Crystal of oxides and non-oxidesIV-2-3) Crystal growth of oxidesIV-2-3) Crystal growth of oxides ((αα-quartz, quartzlike, Calcite, ZnO…)-quartz, quartzlike, Calcite, ZnO…)

IV-2-4IV-2-4) ) How High Pressures can be involved?How High Pressures can be involved?

IV-2-5) Solvothermal Crystal Growth of NitridesIV-2-5) Solvothermal Crystal Growth of Nitrides

.

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SOLVOTHERMAL PROCESSES IN MATERIAL SYNTHESIS

Solvothermal preparation of new materials.Example: Synthesis of Phyllosiloxides: layered oxides isostructural of the natural phyllosilicates.

Solvothermal synthesis of metastable materials.Due to the increase of the chemical reactivity, the synthesis can be kinetically controlled.

Solvothermal synthesis of hybride materials. inorganic/organic systems, inorganic/biological systems.

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to deviate the cracks issued from the matrixmode 1 mode 2


HISTORY :!!!!The first objective:

interphase(fiber/matrix) in composite materials

Solvothermal preparation of new materials

Synthesis of a new class of oxides: Synthesis of a new class of oxides: The PHYLLOSILOXIDESThe PHYLLOSILOXIDES

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- Two different criteria for such an interphase:Two different criteria for such an interphase: layered structure=”mechanical fusible” thermal stability (T≈1000°C) in oxidizing atmosphere

- Analysis of the available layered materials

It is difficult to improve the stability vs. oxygen for graphite and h-BN.Consequently only one way:

How to improve the thermal stability of the phyllosilicates?How to improve the thermal stability of the phyllosilicates?

Thermal stability Stability vs. oxygen

Graphite OK No

h-BN OK No

phyllosilicates No OK


Synthesis of a new class of oxides: The PHYLLOSILOXIDES

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The thermal stability of phyllosilicates is limited by OH groups.2OH- O2-+H2O+

Anionic substitution OH-O2- in the phyllosilicates lattice.

But: correlated with cationic substitutions



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sol-gel process: sol gel aerogel

Conventional Solid State Solvothermal processProcess (500 1000°C) solvent = 2-methoxy-ethanol

precursor = aerogelMixture of 3D silicates T=600°C, 50P150MPa, t24h

single phase

-

-


Synthesis of a new class of oxides:

The PHYLLOSILOXIDES

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I.R.I.R.SpectroscopySpectroscopy

K(Mg2Al) Si4 O12

K Mg3 (Si3Al)O10(OH)2

X. Ray DiffractionX. Ray DiffractionScanning Electron MicroscopyScanning Electron Microscopy H.R.T.MH.R.T.M..

K Mg3 (Si3Al)O10(OH)2 K(Mg2Al) Si4 O12


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II) Solvothermal Processes and the synthesis of novel MaterialsSolvothermal Processes and the synthesis of novel Materials

III)III) Solvothermal Processes and Crystal growthSolvothermal Processes and Crystal growth

III-1)Macroscopic scale and Nano-scaleIII-1)Macroscopic scale and Nano-scale

III-2)Crystal growth at the Macoscopic scaleIII-2)Crystal growth at the Macoscopic scale

III-2-1)General features characterizing the solvothermal III-2-1)General features characterizing the solvothermal growth of large single crystal. growth of large single crystal.(Principle,History,Main (Principle,History,Main

factors,Defects….) factors,Defects….)

III-2-2) Crystal of oxides and non-oxidesIII-2-2) Crystal of oxides and non-oxides

III-2-3) Crystal growth of oxides (III-2-3) Crystal growth of oxides (αα-quartz,quartz--quartz,quartz-like,Calcite,ZnO…)like,Calcite,ZnO…)

III-2-4III-2-4) ) How High Pressures can be involved?How High Pressures can be involved?

III-2-5) Solvothermal Crystal Growth of NitridesIII-2-5) Solvothermal Crystal Growth of Nitrides

I) .

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CONCERNING THE CRYSTAL GROWTH:

How Solvothermal Processes can be involved:

the crystal growth of large single crystalslarge single crystals (oxides or non oxides)

Crystal growth at the macroscopic scale but also,

the design of functional morphologies for nano-crystals for specific applications.

Crystal growth at the nano-scale

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III) Solvothermal Processes and Crystal growthSolvothermal Processes and Crystal growth


III-2)Crystal growth at the Macroscopic scaleIII-2)Crystal growth at the Macroscopic scale

III-2-1)General features characterizing the solvothermal III-2-1)General features characterizing the solvothermal growth of large single crystal. growth of large single crystal.(Principle,History,Main (Principle,History,Main

factors,Defects….) factors,Defects….)





I) ..

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III) Solvothermal Processes and Crystal growthSolvothermal Processes and Crystal growth


III-2)Crystal growth at the Macoscopic scaleIII-2)Crystal growth at the Macoscopic scale

III-2-1) Solvothermal growth of large singleSolvothermal growth of large single crystalcrystal.(Principle,History,Main Features Characterizing the

crystal growth process…)





I) .

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seeds Crystallization zone

Diaphragm

nutrientDissolution zone

Schematic principle for the Solvothermal Crystal Growth

(in the case of a non-retrograde solubility)

PRINCIPLE OF THE SOLVOTHERMAL CRYSTAL

GROWTH

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BRIEF HISTORY OF THE SOLVOTHERMALCRYSTAL GROWTH OF LARGE SINGLE CRYSTALS

The history of the solvothermal Crystal Growth is closely The history of the solvothermal Crystal Growth is closely related to the hydrothermal crystal growth of related to the hydrothermal crystal growth of -quartz-quartz..

due to:

its piezoelectric properties (leading to important applications)

its low temperature domain of stability (T-quartz → T-quartz = 573°C) (impeding the use of conventional

crystal-growth processes)

The elaboration of -quartz single crystals was the first example for industrial developments of Hydrothermal Crystal Growth.

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BRIEF HISTORY OF THE SOLVOTHERMALBRIEF HISTORY OF THE SOLVOTHERMALCRYSTAL GROWTHCRYSTAL GROWTH

First attempts for obtaining small

-quartz crystals.

MURCHISON (1792-1871) described the role of H2O under P, T conditions in the formation of rocks and minerals. SCHAFHÄULT (1845) de SENARMONT (1851)SPEZIA (1842-1912) (Turin-University) using natural crystal as seeds, solution of sodium silicate, silver-lined vessel T = 320-350°C

T- T = 165-180°C200 days -quartz single crystal = 12 mm.

The shortage of natural -quartz from BRAZIL during the second World War: NACHEN (1884-1971) (Frankfurt University)

W.A. and N. WOORTER (Cambridge University)

the first single-crystals through a specific well defined process.

Then industrial developments: U.S., RUSSIA, JAPAN....

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MAIN FACTORS GOVERNING THE SOLVOTHERMAL MAIN FACTORS GOVERNING THE SOLVOTHERMAL CRYSTAL GROWTHCRYSTAL GROWTH

CHEMICAL FACTORSCHEMICAL FACTORS

PHYSICAL FACTORSPHYSICAL FACTORS

KINETICAL FACTORSKINETICAL FACTORS

- nature of the solvent,- nature of the nutrient,- nature of the seeds,- the interactions solvent/ wall of the HP. Vessel.

- the crystal growth temperature (Tgrowth),- the T value,- the pressure value,- the hydrodynamics in the crystal-growth system.

- the kinetics of dissolution,- the kinetics characterizing the diffusion of chemical species,- the crystal growth kinetics,- the duration of the crystal growth.

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MAIN DEFECTS EXISTING IN THE RESULTING CRYSTALS: MAIN DEFECTS EXISTING IN THE RESULTING CRYSTALS: CORRELATIONS WITH THE MAIN FACTORS GOVERNING CORRELATIONS WITH THE MAIN FACTORS GOVERNING

THE SOLVOTHERMAL CRYSTAL GROWTH PROCESSTHE SOLVOTHERMAL CRYSTAL GROWTH PROCESS

CHEMICAL DEFECTS- inclusions of another phase,- chemical impurities: substitution Si4+ Mn+

if n = 4+ no charges compensation ( physical defects in the vicinity of M4+ versus its size) (ex. Ge4+) if n = 3+ (ex: Al3+) charges compensation

→O2- OH- (Hydroxyl-group = O2-/H+ ) or

→M+ alkaline ions near the M3+ (in interstitial position)

PHYSICAL DEFECTS- dislocations (able to trap chemical impurities),- fluids inclusions,- etch-channels…

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CORRELATIONS BETWEEN DEFECTS AND THE MAIN FACTORS GOVERNING THE CRYSTAL GROWTH PROCESS

CHEMICAL DEFECTSCHEMICAL DEFECTS inclusions different phases resulting from the chemical

interactions solvent/walls of the HP vessel, chemical impurities contamination of the nutrient and/or

chemical composition of the solvent.Different aspects:- the identification of the types of ions participating to the lattice

- the incorporation mode : substitutionaly or interstitialy,- the dependence of the concentration of incorporated impurities versus the crystal growth direction and the effect of impurities on growth rate.

PHYSICAL DEFECTSPHYSICAL DEFECTS dislocations → crystal growth rate (vs. T) (etch-channels) vacancies?

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• Solvothermal growth Solvothermal growth

of of

large single crystalslarge single crystals:

→ → OXIDESOXIDES

→ → NON-OXIDES (NON-OXIDES (Nitrides)Nitrides)

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SOLVOTHERMAL PROCESS FOR GROWINGLARGE SINGLE CRYSTALS

Two different domains:

Crystal growth of oxidesCrystal growth of oxides

-quartz (for its piezoelectric properties), AlPO4, GaPO4, GaAsO4 (-quartz-like piezoelectric materials) calcite CaCO3 (optical properties: birefringence and transmission over a wide spectral range) ZnO (wide band gap semiconductor, transparent, dielectric and

piezoelectric properties…) some others oxides as: KTiOPO4 (KTP), hydroxyapatite Ca10(PO4)6(OH)2, LaPO4, -LiBO2, -BaB2O4, RVO4 (R=Y, Gd), KBe2BO3F2

(kBBF), ZrW2O8, -Fe2O3 Zeolites (crystalline aluminosilicates containing pores and cavities of molecular dimensions used as sorbents catalysts, ion exchange materials…)

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SOLVOTHERMAL PROCESS FOR GROWINGLARGE SINGLE CRYSTALS

Crystal growth of non-oxidesCrystal growth of non-oxides

During these last years, strong efforts have been done for controling the solvothermal crystal growth of GaN using a process

derived from -quartz and ZnO solvothermal crystal growth.Ref. “Prospects for the “ammonothermal” growth of large GaN

crystal”T. FUKUDA, D. EHRENTRAUT J. Cryst. Growth. 305, 304-310 (2007)

Such efforts are supported by the existing or potential applications of GaN (opto-electronics, high frequency-high power electronics, fast-speed communication…)

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of of

large single crystalslarge single crystals:

→ OXIDESOXIDES


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SOLVOTHERMAL CRYSTAL GROWTHOF LARGE SINGLE CRYSTALS

SOLVOTHERMAL CRYSTAL GROWTH OF OXIDES

-quartz -quartz

Different solvents (aqueous solutions) have been investigated- NaOH (1M 4 M)- KOH (1M…)- Na2CO3

- NaHCO3, KHCO3

- KCl- NaCl- NaF-pure water

In these solvents the solubility of the nutrient (polycrystalline SiO2) is increased with temperature.

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-quartz -quartz

Nutrient- polycrystalline α-SiO2

- cristobalite

Seeds: natural single crystal of -SiO2

Additives- some additives have been used for limiting the concentration of OH groups into the bulk single crystal, in particular Li2CO3…

The thermodynamical conditions (P, T, T) depend closely of the selected solvent. For exemple using NaOH-1M P 150 MPa

Tgrowth 380-400°C and T 10°C

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-quartz -quartz

Among the role of the thermodynamical parameters on the crystal growth of -SiO2, PRESSUREPRESSURE has not been very investigated.

Variation of the IR coefficient IR coefficient (3500cm-2) for -quartz (Y cut in the Z region) versus the pressure the pressure value usedvalue used for the crystal growth

NaOH(1M)Tcroissance = 350°C,T = 10°C,t = 10 days

Conclusion: if P

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SOLVOTHERMAL CRYSTAL GROWTHOF -QUARTZ

Concentration profiles for aluminum using microprobe X-

versusthe pressure value used for the

crystal growth

NaOH(1M)Tcroissance = 350°C,T = 10 °C,t = 10 days

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Concentration profiles for aluminum using microprobe X-

versusthe pressure value used for the

crystal growth

NaOH(1M)Tcroissance = 350°C, T = 10 °C,t = 10 days

Conclusion:

The [Al] if PFar from the perturbated zone near the seed

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The increase of the pressure value seems to reduce:- the [hydroxyl groups] IR- the [Al3+] microprobe, both being correlated.

In parallel Pressure increases drastically the solubility of polycristalline quartz.

Consequently the concentration of NaOH can be reduced versus pressure.

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SOLVOTHERMAL CRYSTAL GROWTHOF LARGE SINGLE CRYSTALS OF -QUARTZ

Effect of the pressure value on the growth rateEffect of the pressure value on the growth rate

NaOH(1M)Tdissolution = 360°C,T = 10 °C,t = 10 days

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SOLVOTHERMAL CRYSTAL GROWTHOF LARGE SINGLE CRYSTALS OF -QUARTZ

Effect of the crystal growth temperaturecrystal growth temperature on the IR coefficientIR coefficient at 3500 cm-1 (Z cut)

NaOH(1M)P = 150 MPa,T = 35°C,t = 10 days

Conclusion:

P , Tgrowth

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SOLVOTHERMAL CRYSTAL GROWTHOF LARGE SINGLE CRYSTALS OF OXIDES

BERLINITE-AlPOBERLINITE-AlPO44

Three main differences with -quartz

(1)no natural single crystals are available,

(2) the Solubility if the Temperature

(3)The solvents generally developed are different (H3PO4 or H2SO4)

in order to “bypass” the lack of natural seeds berlinite epitaxy on -quartz seeds have been developed.

A.I. MOTCHANY and P.P. CHVANSKIAnnales de Chimie: Science des Materiaux

vol. 26 (2001) p. 199-208

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GaAsOGaAsO44

GaAsO4 is characterized by the highest piezoelectric coupling coefficient for -quartz type materials

Permittivity as a function of piezoelectric coupling constant for -quartz type

O. CAMBON, P. YOT, S. RUL, J. HAINES, E. PHILIPPOT Solid State Sciences5 (2003) p. 469-472

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GaAsOGaAsO44

Same problems than that observed for AlPO4.

Solubility curve of GaAsO4 in 11.5 mole/l H3AsO4

Tdissolution 190°CTgrowth 235°C

O. CAMBON, P. YOT, S. RUL, J. HAINES, E. PHILIPPOT, Solid State Sciences 5, 469 (2003).

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CALCITE: CaCOCALCITE: CaCO33

The hydrothermal process for growing calcite crystals was developed in different countries:

Russia – VNIISIMS (I.V. NEFYODOVA, V.I. LYUTIN, V.L. BORODIN, P.P. CHVANKI, N.I. LEONYUK) in association with Moscow State University.

US – (Dr R. KIWLOCH, R.F. BELT, R.C. PUTTBACH)

France – (F. GENER, M.C. BRICARD, R. LEMETRE, R. AUMONT)

Japan – (K. KIKUTA, S. HIRANO) (K. YANAGISAWA, K. KAGEYAMA, Q. FENG,

I. MATSUSHITA)

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CALCITE: CaCOCALCITE: CaCO33

Different Solvents have been investigated - NH4Cl, NH4Br- LiCl, NaCl, KCl, CaCl2- KNO3, NaNO3, Ca(NO3)2, NH4NO3

- K2CO3

- organic salts

Different orientations of seeds have been used seed plates // rhombohedral face (1011),pinacoidal (0001) and prismatic (1120) faces.

Thermodynamical conditionsT = 250-300°C T 5 - 10°CP 60 – 100 MPa duration 30-120 days

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ZnO ZnO

During these last ten years strong efforts have been developed for preparing high quality single crystals of ZnO.

Why? : ZnO is a transparent dielectric, piezoelectric and wide-band gap material sustaining a lot of important applications:

piezoelectric transducer, gas sensor, optical waveguides, transparent electrode, varistor and SAW filter, UV and blue light-emitting device, opto-electronic and spintronic devices (due to the direct band gap 3.37eV and large exciton-binding energy 60meV).

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ZnOZnO

Roughly ZnO single Crystals have been prepared through 3 different methods:

The flux methodThe flux method (molten salts as PbF2, V2O5, MoO3, B2O3…) the temperature 800-1300°C.Main problems:

- the crystallinity, the size of the single crystals, the difficulty to separate single crystal and solidified flux…

The chemical vapor transport methodThe chemical vapor transport method : chlorine can be used as gazeous transporting agent: ZnO + Cl2 ZnCl2 + ½ O2

G0 being positive at low temperature and becoming negative at high temperature, transport will proceed through the T. (Tgrowth 950-1000°C, T = 10-100°C)Main problems: - the size and the purity of single crystals. The hydrothermal routeThe hydrothermal route

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ZnOZnO

The hydrothermal method comparatively demonstrated:(i) the high quality of crystals,(ii) the scale-up is possible on the basis of the hydrothermal crystal growth of -quartz.

What are the main requirements for hydrothermal growth of ZnO high quality What are the main requirements for hydrothermal growth of ZnO high quality single crystalssingle crystals:

use of alkaline solutions (high concentration), use of a inner container, nutrient: ceramic or pressed tablets, main crystallographic orientation for the seeds (0001), growth conditions T 300-400°C

P 10 – 50 MPa,

D. EHRENTRAUT, H. SATO, Y. KAGAMITANI, H. SATO, A. YOSHIKAWA, T. FUKUDA, Progress in Cryst. Growth Charact. Mater. 52 (2006) p. 280-335

L.N. DEM’YANETS, V.I. LYUTIN, J. Cryst. Growth 310 (2008) p. 993-999

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ZnOZnO

During these last years different research groups have been involved in Solvothermal Crystal Growth of ZnO.

US: Air Force Research Laboratory University of New York and Wagner College

RUSSIA: VNIISIMS Institute of Crystallography R.A.S. Moscow

JAPAN: Tohoku University

CHINA: State Key Lab. WuhanGuilin Research Inst. Guilin

EUROPE: ICMCB-Bordeaux

At the present time 3 in-size bulk ZnO single crystals are accessible.

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SOLVOTHERMAL GROWTHOF LARGE SINGLE CRYSTALS OF OXIDES

ZnO ZnO

Main directions of research in order to help the crystal growth of ZnO comparatively with the crystal growth of -SiO2?

The main problem

How to reduce the concentration of the solvent in alkaline hydroxides?How to reduce the concentration of the solvent in alkaline hydroxides?

→Objective: no liner or no special alloys in order to help the handling of experiments and to reduce the cost.

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Solvothermal processes have been developed for the crystal growth of different oxides -LiBO2

Borate Base materials leading to a variety of optical applications within the deep -UV region. - solvent LiOH (small concentration) C.D. McMILLEN et al. J. Crystal Growth 310 (2008) p. 299-305

Hydroxy-apatite Ca10(PO4)6(OH)2

- M. ASHOK et al. J. Mat. Sci.: Mater. Med. 18 (2005) p. 895-898

-BaB2O4

- A.E. KOKH et al. Inorganic Mater. 41 (2005) p. 60-64

PbTiO3

- MC. GEZABERT, R.A. LAUDISE, R.E. RIMAN, J. Cryst. Growth 197 (1999) p. 195-203

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KBe2BO3F2 (KBBF)(this is the only material that can be achieve direct frequency doubling below 200 nm.) - N. YE, D. TANG J. Crystal Growth 293 (2006) p. 233-335

ZrW2O8

(due to its negative thermal expansion)

- Q. XING et al. J. Crystal Growth 283 (2005) p. 208-214

-Fe3O3

- L.N. DEMIANETS, S.V. POUCHKO, R.V. GAYNUTDINOV J. Crystal Growth 259 (2003) p. 165-178

Zeolites - C.S. CUNDY, P.A. COX, Chem. Rev. 103 (2003) p. 663-701

LaPO4

(for bio- imaging applications) - K. BYRAPPA et al. J. Mater. Sci. DOI 10.1007/s 10853-007-2337-8

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• Solvothermal growth Solvothermal growth of of

large single crystalslarge single crystals::

→ OXIDESHow very High Pressures can be sometimes How very High Pressures can be sometimes

involved?involved? (Basic Researches)


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HOW VERY HIGH PRESSURES HAVE BEEN REQUIRED FOR THE CRYSTAL GROWTH OF SOME OXIDES

Crystal growth of RNiO3 (R= Rare-earth)

“Crystal Growth of RNiO3 perovskites under high oxygen pressure and hydrothermal conditions”J.A. ALONSO, M.J. MARTINEZ-LOPE, M.T. CASAIS, A. MUNOZ, A. LARGETEAU, G. DEMAZEAUMRS Spring Meeting 2005 Symposium Y878 (2005) p. Y3.4.1-Y3.4.14

- Using RNiO3 as nutrient(H2O + KClO3) as solventP 4-6 GPaT 900°C

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HOW VERY HIGH PRESSURES HAVE BEEN REQUIRED FOR THE CRYSTAL GROWTH OF SOME OXIDES

Crystal growth of CaFeO3

M. AZUMA et al. Physica C. 392-396 (2003) p. 22-28 Nutrient: Ca2Fe2O5

Solvent: KClO4, NaCl, CaCl2-6H2OConditions: P 4 GPa, T 1300°C 900°C

Crystal growth of Tl2Ru2O7

D. MORI et al. J. Solid State Chem. 179 (2006) p. 935-940Nutrient: Tl2Ru2O7

Solvent: KClO4, NaClO4

Conditions: P 2-3 GPa, T 1350°C

Crystal growth of SrCu2O3

A. LOEFFERT, C. GROSS, W. ASSMUSJ. Phys.: Condensed Matter 14 (2002) p. 11161-11166 Nutrient: SrO + CuO Conditions: P 3-6 GPa, T 950-1500°C

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of of

large single crystalslarge single crystals::

→ → OXIDESOXIDES

→ NON-OXIDES (NON-OXIDES (Nitrides)Nitrides)

53


SOLVOTHERMAL CRYSTAL GROWTHSOLVOTHERMAL CRYSTAL GROWTHOF LARGE SINGLE CRYSTAL OF NITRIDESOF LARGE SINGLE CRYSTAL OF NITRIDES

Among nitrides, the III-nitrides play an important role for different applications.

- GaN crystal growth started at the beginning of the nineties.

-Different methods have been developed: The high pressure nitrogen solution growth processThe high pressure nitrogen solution growth process

(POROWSKI et al. - Poland) problem: High Pressures (P 1 GPa) and High Temperatures (T

1400°C), Process using a Na fluxProcess using a Na flux (at the end of the 1990’s)

(YAMANE et al. - US, MORI et al. - Japan), Process using an alkaline metal flux (K, Li…) or mixed fluxes (Na, Ca, Process using an alkaline metal flux (K, Li…) or mixed fluxes (Na, Ca,

Li…)Li…)(Y. SONG et al., F. KAWAMURA et al…),

Ammonothermal processAmmonothermal process [DWILINSKI et al. (Poland), COLLADO et al. (France), KOLIS et al. (US), DENIS et al. (France), PURDY et al. (US), FUKUDA et al. (Japan)…]

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SOLVOTHERMAL CRYSTAL GROWTHOF LARGE SINGLE CRYSTAL OF NITRIDES

What are the main problems concerning the Solvothermal crystal growth of GaN?

The nutrientThe nutrient small-size GaN crystals or small-pellets of GaN powder,

gallium metal.

The solventThe solventSolution of NH3 with different types of mineralizers

- basic mineralizers: LiNH2, KNH2

[But under the conditions of supercritical ammonia retrograde solubility]- acidic mineralizers: NH4Cl, NH4Br, NH4I

The solubility of GaN in NH3 depends on the concentration of mineralizer and also on the temperatureT. FUKUDA, D. EHRENTRAUT J. Cryst. Growth 305 (2007) p. 304-310

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SOLVOTHERMAL CRYSTAL GROWTHOF LARGE SINGLE CRYSTAL OF NITRIDES

Main problems for the solvothermal Crystal Growth of GaN.

To increase the solubility at lower temperatureTo increase the solubility at lower temperature Instead of GaN as nutrient use of a more “ionic” nutrient as Li3GaN2 (A. DENIS et al. ICMCB – Bordeaux),

Increase of the pressure 500 MPa , if the crystal growth temperature is low enough

Optimization of the solvent composition

The main objectives being: to improve the crystal growth rateto improve the crystal growth rate, for decreasing the price, and in parallel to decrease the dislocations densityto decrease the dislocations density 104 cm2 102 cm2

in order to be competitive with other processes

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How Solvothermal processes can controlHow Solvothermal processes can control

the morphology of nano-crystals?the morphology of nano-crystals?

« Crystal growth at the nano-scale »

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SOLVOTHERMAL PROCESS and CRYSTAL GROWTH

The crystal growth of materials as nano-particlesThe crystal growth of materials as nano-particles..

As the size is reduced to the nanometer range, the material exhibits specific properties due to quantization effects

[H. GLEITER Mater. Sci. Program. 33, 233 (1989), Y. XIA et al. Advanced Materials 15, 353 (2003)]

In such a case the morphology plays an important role In such a case the morphology plays an important role ((0D0D,,1D,2D)1D,2D)

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THE SOLVOTHERMAL PROCESSES ANDTHE CRYSTAL GROWTH AT THE NANOSCALE

Recently one-dimensionnal (1D) nano-structures (wires, rods, tubes…) have been the focus of intensive research owing to their applications in mesoscopic

physics and fabrication of nanoscale devices.

The formation of a 1D nanostructure depends on two steps:

- the nucleation,- the crystal growth.

In addition for generating nanostructures three main parameters must be controled:

the dimensions, the morphology, the monodispersity (or uniformity)

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Schematic illustrations of the different strategies for achieving 1D growthSchematic illustrations of the different strategies for achieving 1D growth.

A) Induction of 1D morphology through the anisotropic structure,B) confinement by a liquid droplet in the liquid/solid process,C) use of templates,D) use of capping agents able to modify the growth rate in one direction,E) self assembly of OD nanostructure,F) size reduction of 1D microstructure.

Y. XIA et al. Adv. Materials 15 (2003) p. 353-389

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During these last years a strong research activity has been focused on different nanocrystallites with a specific morphology:

Solvothermal growth of ZnO nano-structures.

Solvothermal preparation of InAs nanowiresSolvothermal preparation of InAs nanowires..

Solvothermal synthesis of FePt nanowiresSolvothermal synthesis of FePt nanowires.

……….

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ZnO nanostructuresZnO nanostructures

B. WEN, Y. HUANG, J.J. BOLANDJ. Phys. Chem. C. 112 (2008) p. 106-111

The nanostructures have been prepared through the control of three key experimental parameters:

(1) Solvent compositionSolvent composition: ethanol or a mixture H2O/ethanol.

(2) The use of surfactantsThe use of surfactants: (cetyltrimethyl ammonium bromide) (TAB) in addition of the traditional hexamethylenetetramine (HMTA).

(3) The use of seed layerThe use of seed layer: a 40nm thick ZnO layer was used as growth seeds in order to lower the interfacial energy between the crystal nuclei and the substrate and decreased the nucleation barrier for facilitating the growth of ZnO nanowires.

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ZnO nanostructures

SEM images of ZnO nanwires and nanorods: (c) low-magnification image, (d) high-magnification image.

The length of the nanowires can be experimentally controlled by adjusting the growing time.

B. WEN, Y. HUANG, J.J. BOLANDJ. Phys. Chem. C. 112 (2008) p. 106-111

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InAs nanowiresInAs nanowires

X. XU et al. Nanotechnology 17 (2006) p. 3416-3420.

Instead to use expensive organic arsenic precursors, As2O3 was developed (As2O3 can be dissolved in many organic solvents).

The precursors: As2O3 and InCl3, 4H2O. The reducing agent: NaBH4. A mixture of ethylenediamine, polyethylene glycol and glycol was used as solvent3 NaBH4 + 2As2O3 + 4InCl3 3NaBO2 + 4InAs + 12HCl

The morphology is affected by:

the ratio of ethylenediamine/H2O, the pH value, the temperature.

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FePt nanowires

Example: Solvothermal synthesis of FePt nanowires.Y. HOU, H. KONDOH, R. CHE, M. TAKEGUCHI, T. OHTA

SMALL, 2 (2006) p. 235-238.

Solvent properties – such as polarity, redox potential, viscosity, coordination ability… strongly affect chemical phenomena as: the solubility and transport behavior of the precursors involved in solvothermal processes.

The selection of the solvent (ethylenediamine) has proved to be an ideal solvent for controling the morphology of nanoscale materials – through the formation of stable complex with the bidentate ligand (en).

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FePt nanowires

Pt(acac)2 + ethylenediamine Pt(en)2

+ Fe(CO)5.

T = 180°C P = autogeneous t = 48-96h

With an increase of temperature co-reduction of [Pt(en)2]2+ and thermal decomposition of [Fe(CO)5] led to the formation of FePt nanowires.

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CONCLUSIONSCONCLUSIONS

Whatever the applications of Solvothermal Processes:

The Synthesis of new materialsThe Synthesis of new materials

in particular -if the precursors and the solvent are well selected in order to improve the chemical reactivity-

stabilization of metastable materials

The Crystal Growth of large single crystalsThe Crystal Growth of large single crystalsHistorically = aqueous solutions, ammonia solution

(-SiO2) (GaN)

near future :liquid H2S or organic liquids able to solubilize sulphides on phosphides.

The induction of a specific morphology for nanocrystalsThe induction of a specific morphology for nanocrystals, (morphology adapted to different nano-devices with specific physical properties.)

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the selection of the precursors

the selection of the solvent

the selection of additives

(oxido-reduction, complexing agent, surfactant modifying selected surface energy (h.k.l.)…)

the selection of the thermodynamical conditions PRESSURE-TEMPERATURE

subcritical, supercritical, heterogeneous or homogeneous system.

The control of a Solvothermal ProcessThe control of a Solvothermal Process

is closely dependent on 4 main factors:is closely dependent on 4 main factors:

1 New Trends in Solvothermal Crystal Growth Processes International Seminar on Material Synthesis and Processing (ISMSP-2008) Taipeh (TAIWAN), 26-27 march.

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