preparative methods in inorganic solid state chemistry · pdf filepreparative methods in...

Preparative Methods in Inorganic Solid State ChemistryLecture series given at the Department of Inorganic Chemistry

at University of Bonn, Germany (winter term 2004/05)

R. Glaum

Institut für Anorganische ChemieRheinische Friedrich-Wilhelms-Universität, Bonn (Germany)

http://anorg.chemie.uni-bonn.de/akglhomeemail: [email protected]

http://anorg.chemie.uni-bonn.de/akglhome

Contents

1. Basic ideas and problems about solid state reactions

2. Phase diagrams – Reading and understanding

3. Crystal Growth from a melt

4. Crystal Growth from a flux

5. Hydrothermal/solvothermal syntheses

6. Electrochemical Syntheses

7. Chemical Vapour Transport / Chemical Vapour Deposition

8. Purification of Solids

9. Commercial processes

http://za0510pc5.chemie.uni-bonn.de/akglhome


Reactivity of Solids I.

MgOs + Al2O3,s = MgAl2O4,s

interdiffusion layer, thickness x

= k · x –1dxdt

x = (k' · t) –1/2

parabolic growth

2Al3+ – 3Mg2+ + 4MgOs = MgAl2O4,s

Interface MgO / MgAl2O4:

3Mg2+ – 2Al3+ + 4Al2O3,s = 3 MgAl2O4,s

Interface MgAl2O4,s / Al2O3,s:

Overall reaction:

A. R. West, Solid State Chemistry and ist Applications, Wiley & Sons, 1984.

Spinel MgIIAlIII2O4

cubic, a = 8,081 Å; building units: [MgIIO4] and [AlIIIO6]

O2– Al/Cr3+ Mg2+

chromophor[CrO6]

http://anorganik.chemie.uni-bonn.de/akglhome

http://anorganik.chemie.uni-bonn.de/akglhome

M. C. Escher: Fishes to Birds


Reactivity of Solids II.

NiOs + Al2O3,s = NiAl2O4,s

= k · x –1dxdt

x = (k' · t) –1/2

parabolic growth

2Al3+ – 3Ni2+ + 4NiOs = NiAl2O4,s

Interface NiO / NiAl2O4:

3Ni2+ – 2Al3+ + 4Al2O3,s = 3 NiAl2O4,s

Interface NiAl2O4,s / Al2O3,s:

Overall reaction:formation of NiAl2O4,s

x2 = k'' · t

Wagner mechanism


Reactivity of Solids III.

Problems:high activation temperature required for migration (diffusion) of atoms (ions) in a solid low thermal stability of some reaction products

Solutions:application of high temperatures („shake and bake“; „heatand beat“; brute force methods)providing large surface areas and short diffusion paths for a solid state reaction to happenuse of reactive precursor materialsSolid state reactions via more mobile phases (liquid or gas phase: reactions in melts, hydrothermal synthesis, CVT)


An Example: Synthesis of Na3N

Na3N: anti-ReO3 structure type

Problem:3Nal + 1/2N2,g ≠ Na3Nsvery high activation temperaturefor the educts low thermal stability of thereaction product (Tdecomp ≤ 360°C)

Solution:Intimidly mixed atoms have to bereacted!Co-condensation of Na- and N-atomsT = 4K, followed by slow heating

M. Jansen, Angew. Chem. 2002, 114, 3897.

Gibbs Phase Triangles I.

Gibbs phase triangle for system Ti / P / O



Gibbs Phase Triangles II.

Ternary phase diagrams A / B / C showing differenthomogeineity regions


Gibbs Phase Triangles II.

Gibbs phase triangle for system Co / P / O(T = 800°C)

A CoOB Co3(PO4)2C Co2P2O7D Co2P4O12E CoP4O11F P4O10G P4O6H Co2PI CoPJ CoP2K CoP3

II IV

I

V

VI

III

Co II :Co, Co3(PO4)2, Co2PCo IV:Co2P, Co2P2O7, CoP

A. Schmidt, Dissertation, JLU Gießen, 2002. M. Blum, geplante Dissertation, Uni Bonn.

Oxygen Coexistence Pressure I.

1. Aufstellen der Zersetzungsgleichung :

2 / 7 Co2P2O7,s = 4 / 7 CoPs + O2,g

2. Thermodynamik :

∆RHT = (4/7∆BHT(CoPs) + ∆BHT(O2,g)) - 2/7 ∆BHT(Co2P2O7,s)

??

Van`t Hoff : RT

GK R∆−=ln

RS

RTHK RR ∆+

∆−=ln

M. Blum, geplante Dissertation, Uni Bonn.

Oxygen Coexistence Pressure II.

CoP und Co2P2O7 sind Feststoffe, also ist Kp = p(O2)

Somit folgt aus :

567.4567.4)log( T

SRT

THR

PK∆

+⋅

∆−= log (p(O2))= -29.028 • 1/T + 7.614und

567.4028.29 1053HR∆=− und

567.4614,7 1053SR∆=

molkcalHR /6,1321053 =∆

KmolcalSR ⋅=∆ /77,341053


Oxygen Coexistence Pressure IIIa.

MessprinzipM. Blum, geplante Dissertation, Uni Bonn.

Oxygen Coexistence Pressure IIIb.

Ar mit 1000ppm H2

I

H2/H2O

T

Vorgeschaltete Messzelle

O2

U

I

H2/H2O

T

Nachgeschaltete Messzelle

U

H2/H2OO2

p(O2)=f(T)

MessprinzipM. Blum, geplante Dissertation, Uni Bonn.

Oxygen Coexistence Pressure IV.

Trägergas : Argon mit 1000ppm Wasserstoff

Flußkontrolle ( 5l / h )

Befeuchtung (opt.)

Reaktor mit Probe

Messapparatur

1. Messzelle 2. Messzelle

K.Teske, H. Ullmann, N. Trofimenko, J. Thermal Anal., 49 ( 1997 ) S.1211-1220

Oxygen Coexistence Pressure V.

Beispiel : CoIV (Co2P, Co2P2O7, CoP)

0,0008 0,0009 0,0010 0,0011

-24

-22

-20

-18

-16

-24

-22

-20

-18

-16

04. 02. 01Co4blm1; Auswertung mit I

log(

p(O

2))(p

(O2)

inat

m)

1/T [1/K]

log (p(O2))= 29.028 • 1/T + 7.614


Phase Diagrams I.

incongruentmelting of ABand varioussolid solutions


Phase Diagram MgO – Al2O3


Crystal Growth Techniques I.

Czochralski Verneuil

pullingdirection

heater coil

crucible

growingcrystal

melt

O2 + powder

O2 + H2

flame

droplets

growing crystal

crystal support

(e.g.: Al2(SO4)3 + Cr2(SO4)3)


Verneuil‘s Techniqueca

. 250

cm

powder particel melt in the flame of an H2/O2 burner and crystallize on a crystal seedling; ruby and saphire are grownon an industrial scale applying Verneuil‘s technique

W. J. Moore, Der feste Zustand, Vieweg, 1977.

Synthetische Kristalle

Synthetische Kristalle besitzen die gleiche chemische Zusammensetzung wie natürlich gewachsene.

W. Schumann, „Edle Steine“, BLV Verlagsges. 1993.

Crystal Growth Techniques II.

Stockbarker Bridgman

zone melting

purification and crystallisation of metals


Flux Growth Techniques I.

Reasons for application of the technique:

1) Desired material does not melt or has very high m.p.

2) Lowering of crystallization temperature

3) Improvement of crystal quality

4) Avoiding non-stoichiometry

B. R. Pamplin (ed.), Crystal Growth, Pergamon Press, 1975.

Flux Growth Techniques II.

Choice of a flux:

1) High solubility for desired compound

2) High temperature coefficient of solubility

3) No miscibility with the compound to be crystallized

4) Inertness towards dissolved material and crucible


Flux Growth Techniques III.

Selected Examples - Oxides


Flux Growth Techniques IV.

Means of achieving crystallization from fluxed melts:

EF: temperature gradient(transport)

A,B,C:slow cooling

AD: evaporation of solventOstwald-Miers-Region


Flux Growth Techniques V.

Temperature profile (pendulum) for seed reduction:


Flux Growth Techniques VI.

Modified flux growth

cfg. zone melting


Flux Growth Techniques VII.

K.-Th. Wilke, J. Bohm, Kristallzüchtung, DVW 1988.

elements, borides,carbides, pnictidesfrom metallic fluxes

Hydrothermal Synthesis I.te

mpe

ratu

re

volumedensity

liquidphase

gas

phas

e

two phase

p, T diagramof water

critical point


Hydrothermal Synthesis II.

p, T diagramof water

constant volume

various percen-tages % of fillingof an autoclave


Hydrothermal Synthesis III.

Solubilities under hydrothermal conditions1a) SiO2 – NaOH 450°C1b) SiO2 – Na2CO3 450°C2a) Al2O3 – NaOH 430°C2b) Al2O3 – Na2CO3 430°C3) LiGaO2 – NaOH 400°C4a) ZnO – NaOH 360°C4b) ZnO – KOH 360°C5a) ZnS – KOH 450°C5b) ZnS – KOH 360°C6) KTa0.65Nb0.35O3 – KOH

650°C


Hydrothermal Synthesis IV.

Steel autoclaves


Hydrothermal Synthesis V.

Solubilitiy of SiO2 in water (left) and NaOH (right)

temperature

solu

bilit

y

250 atm

500 atm

750 atm

1000 atm

0,5n NaOH (80% filling)


Hydrothermal Synthesis VI.

B. R. Pamplin, Crystal Growth, Pergamon Press, 1975.

α - β Transition for Quartz

Structural relationship

P 62 2 2

α-SiO2 ↔ β-SiO2, TT = 573°C (2nd order)

t2

P 32 2 1

H. Bärnighausen, Commun. Math. Chem. 1984, 9, 139.

Chemical Vapour Transport I.

Chemical Vapour Transport: Migration of an otherwise immobilesolid in a chemical potential gradient via a mobile phase (gas orliquid)

Migration in a temperature gradient

Cl2,g Fe2O3,s

transport agentT(source)

T(sink)

isothermal transport; short distance transport; mineralisation effects;hydrothermal syntheses



Chemical Vapour Transport II.

Chemical Transport Physical Transport(Destillation, Sublimation)

without transport agent

direction always from hot to cold(T2 6 T1)

needs a transport agent (but: autotransport)

migration from hot to cold (T2 6T1) as well as from cold to hot(T1 6 T2) possible

Applications:van Arkel / de Boer - Methodpurification of solidshalogen lampscrystal growthmineral formation / Geology

Applications:purification of solids and liquidsfreeze drying



Natural Hematite Fe2O3



Chemical Vapour Transport III.

Questions:

Cl2,g Fe2O3,s

transport agent

Fe2O3,s + 3 Cl2,g = 2 FeCl3,g + 3/2 O2,g “transport reaction”

Which solids can be “transported”?Optimum experimental conditions (TA; T)?Speed of the migration (deposition); migration rate?

transportingspecies

FeCl3,g; O2,g



Chemical Vapour Transport IV.


The migration direction is determined by the sign of the reactionenthalpy of the transport reaction:

endothermic, ∆RHT > 0 Y T2 6 T1

exothermic, ∆RHT < 0 Y T1 6 T2(Def.: T1 < T2)

Examples: Oxides / chlorineChlorides, bromides / Al2X6

Si (Ti, Fe and other metals) / iodine

endotheric

exothermic

Estimation of the sign of the reaction enthalpy by consideration ofbond energies of educts and products

Thermodynamics



Chemical Vapour Transport V.


“transport equilibrium”K

P FeCl P OP ClP =

⋅23

3 22

32

( ) ( )( )

/

(favorable: KP . 1; ∆RG . 0)

log ( ), ,

K TH

TS

PR T R T= −

⋅+

∆ ∆4 567 4 567

Gibbs-Helmholtz-equation∆ ∆ ∆R T R T R TG H T S= − ⋅(selection of T)

van t’Hoff-equation

Thermodynamics



Chemical Vapour Transport VI.

Experimental setting and definitions

ABK

ampoule dimensions: l .11cm; q . 2,0 cm2; V . 22 cm3

V(source) : V(sink) . 2 : 1

Diffusion length s: 8 - 10 cm

SBK T(source)

T(sink)V(source)

V(sink)



Chemical Vapour Transport VII.

Calculation of partial pressures for CVT of Fe2O3,s using chlorine:

Fe2O3,s + 3 Cl2,g = 2 FeCl3,g + 3/2 O2,g

KP FeCl P O

P ClP =⋅2

33 2

23

2

( ) ( )( )

/

P(Cl2)T1, T2; P(FeCl3)T1, T2; P(O2)T1, T2; ΣPT1, T2 (8 unknown)

P FeCl P O( ) ( )343 2=

(2 Gl.)

(2 Gl.)

Σ PT1, T2 = P(Cl2)T1, T2 + P(FeCl3)T1, T2 + P(O2)T1, T2

n°(Cl2) = [(VT1/R@T1)(P(Cl2)T1 + 3/2 P(FeCl3)T1] + [(VT2/R@T2)(P(Cl2)T2 + 3/2 P(FeCl3)T2]

(2 Gl.)

Σ PT1 = Σ PT2



Chemical Vapour Transport VIII.

Partial pressure calculation for CVT of Fe2O3,s using chlorine:

Fe2O3,s + 3 Cl2,g = 2 FeCl3,g + 3/2 O2,g

P(Cl2)T1, T2; P(FeCl3)T1, T2; P(O2)T1, T2; ΣPT1, T2 (8 unknown pressures)

2 x -60,6

Exp. conditions: V = 22cm3; V(source) : V(sink) = 2 : 1 P°(Cl2) = 1 atm bei 298 K; n° = 0,982 mmol

3/2 x 0,03 x 0,0-196,82 x 82,2 3/2 x 49,03 x 53,320,9

∆RH298 = 75,6 [kcal / mol]

∆RS298 = 57,1 [cal / mol@K]



Chemical Vapour Transport IX.

Quelle Senke0

1.000

2.000

3.000

4.000

5.000

P(gesamt) P(Cl2,g) P(FeCl3,g) P(O2,g)

Partial pressures as a function of temperature: Partial pressures as a function of temperature:

Ptotal P(Cl2) P(FeCl3) P(O2)T(source) T(sink)



Chemical Vapour Transport X.

Prerequisit for the application of the diffusion model:Diffusion between source and sink is the rate determining step of thewhole migration/deposition process

migration / deposition:(mechanism)

1.) Reaction of ABK with transport agent2.) evaporation of volatile species (1. phase transfer reaction)3.) “migration” from source to sink4.) seed formation5.) Crystal growth (2. phase transfer reaction)



Chemical Vapour Transport XI.

Transport formula derived by Harald Schäfer

, [ ],

nij

PP

T qs

D molAC= ⋅ ⋅

⋅⋅ ⋅ ⋅ −∆

Σ

0 8

0318 10

nA i, j

∆Pc

ΣP T q s

D0

Mole transported solid stoichiometric coefficients partial pressure difference [atm]

total pressure[atm] average temperature of diffusion path [K] cross section of diffusion path [cm2] length of diffusion path [cm] mean diffusion coefficient; 0,1 [cm2@sec-1]



Transport of Metals I.

Zrs + 4 Ig = ZrI4,g; 280 1450°C

Purification of Zirconium following van Arkel / de Boer:

(similarly: Ni, Cu, Fe, Cr, Si, Ti, Hf, Th, V, Nb, Ta, U)

Mos + 5/2 Cl2,g (5 Clg) = MoCl5,g; 400 1400°C

Ws + 3 Cl2,g (6 Clg) = WCl6,g; 400 1400°C

Nis + 4 COg = Ni(CO)4,g; 80 200°C

Purification of Nickel using the Mond-process:

(thermal stability of halogenide)

(vgl. H. Schäfer, Chemische Transportreaktionen, Verlag Chemie (1962))



Transport of Metals II.

e. g.: Ms + 2 Clg = MCl2,g; 800 1000°C

Transport of Fe and Ni using halogens (exothermic):

thermal instability of halides, e. g.:Rhs + 3/2 Cl2,g = RhCl3,g(s) (Y no transport)

Transport of noble metals:

(vgl. H. Schäfer et al., Z. anorg. allg. Chemie 286 (1956) 42.)

Transport of Fe and Ni using hydrogen halides (endothermic):e. g.: Ms + 2 HClg = MCl2,g + 2 H2,g; 1000 800°C

(vgl. H. Schäfer et al., Z. anorg. allg. Chemie 414 (1975) 137.)

increased volatility of halides by gas complex formation, e. g.:Rhs + 3/2 Cl2,g + Al2Cl6,g = RhAl2Cl9,g; 600 800°C



Transport of Oxides I.

Fe2O3,s + 3 Cl2,g = 2 FeCl3,g + 3/2 O2,g; 1000 900°C

Chlorine as transport agent:

Problem: a) frequently unfavourabel equilibria; b) transport of lower(stronly reducing oxides) is impossible Y Oxidation

TiO2,s + 2 Cl2,g = TiCl4,g + 2 O2,g; 900 800°C

MoO3,s + Cl2,g = MoO2Cl2,g + 1/2 O2,g; 900 800°C

Nb2O5,s + 3 Cl2,g = 2 NbOCl3,g + 3/2 O2,g; 1000 900°C

Solution: avoiding “free” oxygen; using non-oxidising transportagents (HCl, TeCl4, TaCl5, PI3)



Transport of Oxides II.

Fe2O3,s + 6 HClg = 2 FeCl3,g + 3 H2Og; 900 800°C

Non-oxidising transport agents:

Problems: occuring of solid (condensed) binary (halides) and ternary(tantalates; phosphates) phases

Ti3O5,s + 12 HClg = 3 TiCl4,g + 5 H2Og + H2,g; 900 800°C

MoO3,s + TeCl4,g = MoO2Cl2,g + TeOCl2,g; 900 800°C

Ta2O5,s + 3 TaCl5,g = 5 TaOCl3,g; 1000 900°C

3 TiO2,s + 4 PI3,g = 3 TiI4,g + P4O6,g; 900 800°C



Transport of Complex Oxides I.

CoNb2O6,s + 5/2 Cl2,g = CoCl2,g + NbOCl3,g + 5/2 O2,g

Transport behaviour similar to binary components:

lower solubility generally means lower solubility difference (lowermigration rate)

(Co1-xZnx)Os + Cl2,g = (1-x) CoCl2,g + x ZnCl2,g + 1/2 O2,g

Stabilisation of binary componenten by formation of the ternaryphase leeds to lower solubility in the gas phase of the ternary phasein comparison to the binary phases.

NiTiO3,s + 3 Cl2,g = NiCl2,g + TiCl4,g + 3/2 O2,g



Transport of Complex Oxides II.

ZnSO4,s + Cl2,g = ZnCl2,g + SO2,g + 1/2 O2,g

Chemical Vapour Transport of anhydrous sulfates:

Fe2(SO4)3,s + 3 Cl2,g = 2 FeCl3,g + 3 SO3,g + 3/2 O2,g

Fe2(SO4)3,s + 3 Cl2,g = 2 FeCl3,g + 3 SO2,g + 3 O2,g FeSO4,s + 2 HClg = FeCl3,g + SO2,g + H2Og + O2,g

(formation of Fe2O3,s)

NiSO4,s + Cl2,g = NiCl2,g + SO3,g + 1/2 O2,g

Al2(SO4)3,s + 3 SOCl2,g = 2 AlCl3,g + 6 SO2,g

2 VO(SO4)s + 3 Cl2,g = 2 VOCl3,g + 2 SO3,g + O2,g

NiSO4,s + PbCl2,g = PbSO4,s + 2 NiOs + SO2,g + Cl2,g



Transport of Halides I.

Caveat: migration in a temperature gradient frequently must be regarded as distillation or sublimation!

CrCl3,s + 1/2 Cl2,g = CrCl4,g; 800 700°C

MoBr3,s + MoBr5,g = 2 MoBr4,g; 475 250°C

Transport via higher halogenides (TR accompanied by oxidation):

(vgl. H. Schäfer, Z. anorg. allg. Chemie 414 (1975) 137.)

MoBr2,s + HgBr2,g = MoBr4,g; 1000 900°C

2 AlCl3,g = Al2Cl6,g

Transport via formation of gaseous complexes using AlCl3, AlI3,FeCl3 as complexing agent:

∆DimH298 = -30,1 [kcal / mol]; ∆DimS298 = -36,9 [cal / mol@K]



Transport of Halides II.

Dissoziation behaviour of Al2Cl6,g

(compare also dimerisation of CoCl2,g and other halides)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

400 600 800 1000 1200 1400 1600

temperature [K]

Al2Cl6,g

AlCl3,g



Transport of Halides III.

Compositions of gaseous complexes: MCl · AlCl3; n MCl · n AlCl3;MCl2 · AlCl3; MCl2 · 2 AlCl3; MCl3 · AlCl3; MCl3 · 3 AlCl3; MCl4 · 2 AlCl3; MCl5 · AlCl3;

(vgl. H. Schäfer, Angew. Chemie 88 (1976) 775.)



Transport of Halides IV.

Examples (synthesis of crystaline, anhydrous halogenides):

2 CrCl3,s + 3 Al2Cl6,g = 2 CrAl3Cl12,g

CoBr2,s + Al2Br6,g = CoAl2Br8,g; 400 300°C

( H. Schäfer et al., J. Less-Common Met. 61 (1978) 47.)

But:

CrCl2,s + Al2Cl6,g = CrAl2Cl8,g; 450 350°C

Pt (excess) + Br2,s + Al2Br6,g Y PtBr3,g; 400 350°C

Pd (excess) + I2,s + Al2I6,g Y Pd2Als + I2,g; T: 350 - 600°CTransport of Pd2Als: 375 600°C

( H. Schäfer, Angew. Chemie 88 (1976) 775.)



Zeolithe M2/zO · Al2O3 · x SiO2 · y H2O

[TO4]-Gruppen als Bausteine

Linde A

Linde X/Y, Faujasit4

Sodalith

Ein molekularer Baukasten

Löcher mit SiO2 drumherum

Sodalith Linde X/Y, FaujasitLinde A

Zeolithe besitzen Hohlräume, in die Moleküle oder Ioneneingelagert werden können.

Synthese von Zeolithen

SiO2haltige Verbindungenz.B. Wassergläser, Kieselsole

+ Natronlauge, Temperatur > 50°C, hydrothermale Reaktionsbedingungen

Zeolith

Al2O3haltige Verbindungenz.B. Aluminiumhydoxide, Aluminate, Kaoline

Anwendungen von ZeolithenEigenschaft Anwendung

AdsorptionIsolierglasKühlmittel

Dynamische Adsorption Trocknung und Reinigung von Erdgas, Spaltgas; Luftzerlegung

Trenneigenschaften Alkane / Isoalkane Trennung,

Ionenaustausch Waschmittel, Abwasserreinigung

Katalyse Fließbettcracken, Hydrocracken, Methanolumwandlung

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