Preparative Methods in Inorganic Solid State Chemistry

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Preparative Methods in Inorganic Solid State Chemistry

Lecture series given at the Department of Inorganic

Chemistry at University of Bonn, Germany (winter term 2014)

R. Glaum

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

http://www.glaum.chemie.uni-bonn.de email: rglaum@uni-bonn.de

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Reactivity of Solids I.

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

MgO_s + Al₂O_3,s = MgAl₂O_4,s interdiffusion layer, thickness x

= k · x ^–1 dx

dt x = (k' · t) ^–1/2

parabolic growth

2Al³⁺ – 3Mg²⁺ + 4MgO_s = MgAl₂O_4,s

Interface MgO / MgAl₂O₄:

3Mg²⁺ – 2Al³⁺ + 4Al₂O_3,s = 3 MgAl₂O_4,s

Interface MgAl₂O_4,s / Al₂O_3,s:

Overall reaction:

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Spinel Mg

^II

Al

^III₂

O

₄

cubic, a = 8,081 Å; building units: [Mg^IIO₄] and [Al^IIIO₆]

O^2– Al/Cr³⁺ Mg²⁺

chromophor [CrO₆]

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M. C. Escher: Fishes to Birds

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Reactivity of Solids II.

NiO_s + Al₂O_3,s = NiAl₂O_4,s

= k · x ^–1 dx

dt x = (k' · t) ^–1/2

parabolic growth

2Al³⁺ – 3Ni²⁺ + 4NiO_s = NiAl₂O_4,s

Interface NiO / NiAl₂O₄:

3Ni²⁺ – 2Al³⁺ + 4Al₂O_3,s = 3 NiAl₂O_4,s

Interface NiAl₂O_4,s / Al₂O_3,s:

Overall reaction:

formation of NiAl₂O_4,s

x

²

= k'' · t

Wagner mechanism

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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“; „heat and beat“; brute force methods)

providing large surface areas and short diffusion paths for a solid state reaction to happen

use of reactive precursor materials

Solid state reactions via more mobile phases (liquid or gas phase: reactions in melts, hydrothermal synthesis, CVT)

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An Example: Synthesis of Na

₃

N

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

Na₃N: anti-ReO₃ structure type

Problem:

3Na_l + 1/2N_2,g

≠

^Na₃^N_s

very high activation temperature for the starting materials

low thermal stability of the

reaction product (T_decomp ≤ 360°C)

Solution:

Intimidly mixed atoms have to be reacted!

Co-condensation of Na- and N-atoms T = 4K, followed by slow heating

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Synthesis of RuSb

₃

A. L. E. Smalley, M. L. Jespersen, D. C. Johnson, Inorg. Chem. 2004, 43, 2486.

RuSb₃: metastable Skutterudite

Problem:

Ru_s + 3 Sb_s

≠

^RuSb_3,s high activation temperature for the educts (Ru_s)

Ru_s + 3 Sb_s

=

^RuSb_2,s ^{+ ¼ Sb}_4,g

m.p.(Sb) = 631°C; b.p.(Sb)

=

^1750°C

RuSb_3,s + RuSb_2,s + Sb_s

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Synthesis of RuSb

₃

A. L. E. Smalley, M. L. Jespersen, D. C. Johnson, Inorg. Chem. 2004, 43, 2486.

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Structures of ReO

₃

and Skutterudite

Skutterudite: CoAs₃ ReO₃

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An example from „real life“ (1)

S.C. Roy, planned Ph. D. thesis, 2014, University of Bonn.

J. J. Moore, H. J. Feng, Prog. Mater. Sciences 1995, 39, 243-273.

Synthesis of Cr^III(W^VIO₂)₂(P₂O₇)(PO₄) with high specific surface area ( low-temperature synthesis)

Starting materials: (NH₄)₆W₁₂O₃₉∙5H₂O, 6 Cr(NO₃)₃∙9H₂O, 18(NH₄)₂HPO₄, glycine, HNO₃

The concept: formation of a gel (coordination polymer) upon evaporation;

Glycin & Ammonia (fuel) react with HNO₃ (oxidant) in a com- bustion reaction; formation of gaseous products and of a non- volatile, amorphous solid

Diffusion barrier: problem and chance in solid state chemistry

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An example from „real life“ (1)

S.C. Roy, planned Ph. D. thesis, 2014, University of Bonn.

Keggin-type compound

2 (NH₄)₃PW₁₂O₄₀ + „Cr₁₂P₃₄O₈₅“ ReO₃-type compound

(Cr^III_0.167W^VI_0.333P^V_0.500)O_2.50_0.5 W^VOPO₄-type compound

(Cr^III_0.333W^VI_0.667)OPO₄

Complete crystal chemical differentiation

Cr^III(W^VIO₂)₂(P₂O₇)(PO₄)

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Keggin-Anion [P(Mo₃O₁₀)₄]^3–

An example from „real life“ (1)

Keggin-type compound 2 (NH₄)₃PW₁₂O₄₀

+

„Cr₁₂P₃₄O₈₅“

S. C. Roy, planned Ph.D. Thesis 2014; P. Armand, D. Granier, A. van der Lee, Acta Crystallogr. 2007, E63, i191.

Close the balance for all components!

Cr₁₂W₂₄P₃₆O_x

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ReO₃

ReO₂(PO₄)

Re^VIO₃ (a = 3.46 Å)

W^VIO₃ (a = 3.84 Å)

(CrÎII_0.167W^VI_0.333P^V_0.500)O_2.5_0.5 (a = 3.78 Å) (CrÎII_0.10VÎV_0.10W^VI_0.30P^V_0.500)O_2.5_0.5 ?

(Cr^III_0.10V^V_0.10W^VI_0.30P^V_0.500)O_2.50O_0.05_0.45 ?

S. C. Roy, planned Ph.D. Thesis 2014; R. Glaum, S. Islam et. al., Z. anorg. allg. Chem. 2013, 639, 2463.

ReO

₃

type structures containing phosphate?

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W^VOPO₄: a = 6.5538(4)Å, b = 5.2237(8)Å, c = 11.1866(8) Å, β = 90.332(7)°

(Cr^III_0.33W^VI_0.67)OPO₄: a = 6.473(1)Å, b = 5.1569(4) Å, c = 11.049(2) Å, β = 90.11(1)°

Structure of (Cr

^III_0.33

W

^VI_0.67

)OPO

₄

(Cr^III_0.33W^VI_0.67)OPO₄:

(CrÎII_0.20VÎV_0.20W^VI_0.60)OPO₄? (FeÎII_0.20VÎV_0.20W^VI_0.60)OPO₄?

S. C. Roy, planned Ph.D. Thesis 2014.

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C2/m, Z = 16, a = 37.016(3) Å, b = 12.756(1) Å, c = 9.428(1) Å, β =102.275(9)°

Structure of Cr

^III

(W

^VI

O

₂

)

₂

(P

₂

O

₇

)(PO

₄

)

S. C. Roy, planned Ph.D. Thesis 2014.

Homogeneity range for V^III(W^VIO₂)₂(P₂O₇)(PO₄): (W_1−xV_x)OPO₄, 0.33 ≤ x ≤ 0.40

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Gibbs Phase Triangles I.

Gibbs phase triangle for system Ti / P / O

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Gibbs Phase Triangles II.

Ternary phase diagrams A / B / C showing different

homogeineity regions

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Gibbs Phase Triangles III.

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

A CoO

B Co₃(PO₄)₂ C Co₂P₂O₇ D Co₂P₄O₁₂ E CoP₄O₁₁ F P₄O₁₀ G P₄O₆ H Co₂P

I CoP

J CoP₂

K CoP₃

II IV

I

V

VI III

Co II :

Co, Co₃(PO₄)₂, Co₂P Co IV:

Co₂P, Co₂P₂O₇, CoP

M. Blum, K. Teske, R. Glaum, Z. Anorg. Allg. Chem. 2003, 629, 1709.

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Oxygen Coexistence Pressure I.

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

flux control ( 5l / h )

carrier gas : argon + 1000 ppm hydrogen

up stream cell

down stream cell

moisturizer (opt.)

reactor with sample

coulometric / potentiometric determination of p(O₂)

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Oxygen Coexistence Pressure II.

Messprinzip

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Oxygen Coexistence Pressure III.

Beispiel : CoIV (Co₂P, Co₂P₂O₇, CoP)

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

-24 -22 -20 -18 -16

04. 02. 01

Co4blm1; Auswertung mit I log(p(O 2))(p(O 2)inatm)

1/T [1/K]

log (p(O₂))= 29.028 • 1/T + 7.614

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Oxygen Coexistence Pressure IV.

1. What is the decomposition reaction?

2 / 7 Co₂P₂O_7,s = 4 / 7 CoP_s + O_2,g

2. Thermodynamics :

∆_rH_T= (4/7∆_fH_T(CoP_s) + ∆_fH_T(O_2,g)) - 2/7 ∆_fH_T(Co₂P₂O_7,s)

? ?

Van`t Hoff :

RT K = − ∆^RG ln

R S RT

K ^RH ∆^R

∆ +

−

= ln

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Oxygen Coexistence Pressure V.

29.028 1053

4.567

rH

− = ∆ 7,614 ¹⁰⁵³

4.567

rS

= ∆

1053 132,6 kcal mol 1

RH ⁻

∆ = ⋅

1 1

1053 34,77 cal mol K

rS ⁻ ⁻

∆ = ⋅ ⋅

CoP and Co₂P₂O₇ are solids (a = 1), therefore K_p = p(O₂) than follows :

log 4.567 4.567

r T r T

p H S

K T

∆ ∆

= − +

⋅

2 1

log (O )p 29.028 7.614

= − ⋅ +T

comparison of coefficients yields:

and eventually:

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26

Cobaltoxide

homogeneity ranges of CoO(s) and Co₃O₄(s) are not included

CoO(s) melts at higher oxygen pressure, only Co₂O₃(s) is only badly characterised

Stability ranges of Co(s), CoO(s), and Co₃O₄(s) as functions of T and p(O₂)

P. Schmidt, Thermodynamische Analyse der Existenzbereiche fester Phasen – Prinzipien der Syntheseplanung in der Anorganischen Festkörperchemie, Habilitationsschrift,

TU Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1200397971615-40549

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Oxygen co-existence pressures for binary systems I.

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Oxygen Co-existence pressures for binary systems II.

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Oxygen Co-existence pressures for binary systems III.

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30

Oxygen Co-existence pressures for binary systems IV.

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Metallo-thermic metal oxide reduction I.

Reduction of Fe₂O₃(s) by aluminium is no problem!

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32

Reduction of HfO₂(s) is impossible by aluminium but works with calcium!

Metallo-thermic metal oxide reduction II.

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33

components behave in the ternary system like the binaries!

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35

Redox equilibria between oxides of iron and titanium

Only the combinations FeÎII/TiÎV and FeÎI/TiÎV are stable!

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36

Redox equilibria between oxides of iron and titanium

p(O₂) rises from metallic titanium to iron(II) oxide.

I) II) III) IV)

sollid solutions:

FeÎII₂TiÎV₂O₇ FeÎII₂TiÎVO₅ FeÎITiÎVO₃ FeÎI₂TiÎVO₄

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37

Redox equilibria in the system Fe / V / O

In ternary oxides the combinations FeÎI/VÎII, FeÎI,III/VÎII, FeÎI,III/VÎII,IV, FeÎII/VÎV and FeÎII/V^V are stable!

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Phase Diagrams I.

incongruent melting of AB and various solid solutions

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Phase Diagram MgO – Al

₂

O

₃

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Crystal Growth Techniques I.

Czochralski Verneuil

pulling direction

heater coil crucible growing

crystal melt

O₂ + powder

O₂ + H₂

flame droplets

growing crystal

crystal support

(e.g.: Al₂(SO₄)₃ + Cr₂(SO₄)₃)

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Verneuil‘s Technique

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

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

ca. 250 cm

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Synthetische Kristalle

Synthetische Kristalle besitzen die gleiche chemische Zusammensetzung wie natürlich gewachsene.

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

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Crystal Growth Techniques II.

Stockbarker Bridgman

zone melting

purification and crystallisation of metals

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Flux Growth Techniques I.

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

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

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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

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Flux Growth Techniques III.

Selected Examples - Oxides

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Flux Growth Techniques IV.

Means of achieving crystallization from fluxed melts:

EF:

temperature gradient

(transport) A,B,C:

slow cooling AD:

evaporation of solvent

Ostwald-Miers-Region

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Flux Growth Techniques V.

Temperature profile (pendulum) for seed reduction:

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Flux Growth Techniques VI.

Modified flux growth

cfg. zone melting

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Flux Growth Techniques VII.

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

elements, borides, carbides, pnictides from metallic fluxes

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Hydrothermal Synthesis I.

temperature

volume density liquid

phase

gas phase

two phase

p, T diagram of water

critical point

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Hydrothermal Synthesis II.

p, T diagram of water

constant volume various percen- tages % of filling of an autoclave

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Hydrothermal Synthesis III.

Solubilities under hydrothermal conditions

1a) SiO₂ – NaOH 450°C 1b) SiO₂ – Na₂CO₃ 450°C 2a) Al₂O₃ – NaOH 430°C 2b) Al₂O₃ – Na₂CO₃ 430°C 3) LiGaO₂ – NaOH 400°C 4a) ZnO – NaOH 360°C 4b) ZnO – KOH 360°C 5a) ZnS – KOH 450°C 5b) ZnS – KOH 360°C

6) KTa_0.65Nb_0.35O₃ – KOH 650°C

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Hydrothermal Synthesis IV.

Steel autoclaves

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Hydrothermal Synthesis V.

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

temperature

solubility

250 atm

500 atm 750 atm 1000 atm

0,5n NaOH (80% filling)

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Hydrothermal Synthesis VI.

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

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α ^- β Transition for Quartz

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

Structural relationship

P 6₂2 2

α-SiO₂ ↔ β-SiO₂, T_T = 573°C (2nd order) t2

P 3₂ 2 1

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Chemical Vapour Transport I.

Chemical Vapour Transport: Migration of an otherwise immobile solid in a chemical potential gradient via a mobile phase (gas or liquid)

Migration in a temperature gradient

Cl_2,g Fe₂O_3,s

transport agent

T(source)

T(sink) isothermal transport; short distance transport; mineralisation effects;

hydrothermal syntheses

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

Applications:

van Arkel / de Boer - Method purification of solids

halogen lamps crystal growth

mineral formation / Geology

Applications:

purification of solids and liquids freeze drying

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Natural Hematite Fe

₂

O

₃

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Chemical Vapour Transport III.

Questions:

Cl_2,g Fe₂O_3,s

transport agent

Fe₂O_3,s + 3 Cl_2,g = 2 FeCl_3,g + 3/2 O_2,g “transport reaction”

Which solids can be “transported”?

Optimum experimental conditions (TA; T)?

Speed of the migration (deposition); migration rate?

transporting species

FeCl_3,g; O_2,g

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Chemical Vapour Transport IV.

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

endothermic, ∆_RH_T > 0 Y T₂ 6 T₁

exothermic, ∆_RH_T < 0 Y T₁ 6 T₂ (Def.: T₁ < T₂) Examples: Oxides / chlorine

Chlorides, bromides / Al₂X₆

Si (Ti, Fe and other metals) / iodine

endotheric

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

Thermodynamics

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Chemical Vapour Transport V.

“transport equilibrium”

K P FeCl P O

P = ² P Cl₃ ⋅ ^{3 2} ₂

3

2

( ) ( )

( )

/

(favorable: K_P . 1; ∆_RG . 0)

log ( )

, ,

K T H

T

S

P

R T R T

= − ∆ ⋅ + ∆

4 567 4 567

Gibbs-Helmholtz-equation

∆ _RG_T = ∆ _RH_T − ⋅T ∆ _RS_T

(selection of T) van t’Hoff-equation

Thermodynamics

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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)

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Chemical Vapour Transport VII.

Calculation of partial pressures for CVT of Fe₂O_3,s using chlorine:

Fe₂O_3,s + 3 Cl_2,g = 2 FeCl_3,g + 3/2 O_2,g

K P FeCl P O

P = ² P Cl₃ ⋅ ^{3 2} ₂

3

2

( ) ( )

( )

/

P(Cl₂)_{T1, T2}; P(FeCl₃)_{T1, T2}; P(O₂)_{T1, T2}; ΣP_{T1, T2} (8 unknown)

P FeCl( ₃) = ⁴₃ P O( ₂ )

(2 Gl.) (2 Gl.)

Σ P_{T1, T2} = P(Cl₂)_{T1, T2} + P(FeCl₃)_{T1, T2} + P(O₂)_{T1, T2} n°(Cl₂) = [(V_T1/RT1)(P(Cl₂)_T1 + 3/2 P(FeCl₃)_T1]

+ [(V_T2/RT2)(P(Cl₂)_T2 + 3/2 P(FeCl₃)_T2] (2 Gl.) Σ P_T1 = Σ P_T2

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Chemical Vapour Transport VIII.

Partial pressure calculation for CVT of Fe₂O_3,s using chlorine:

Fe₂O_3,s + 3 Cl_2,g = 2 FeCl_3,g + 3/2 O_2,g P(Cl₂)_{T1, T2}; P(FeCl₃)_{T1, T2}; P(O₂)_{T1, T2}; ΣP_{T1, 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 0,0 3 x 0,0

-196,8

2 x 82,2 3/2 x 49,0 3 x 53,3

20,9

∆_RH₂₉₈ = 75,6 [kcal / mol]

∆_RS₂₉₈ = 57,1 [cal / mol@K]

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Chemical Vapour Transport IX.

Partial pressures as a function of temperature:

P_total P(Cl₂) P(FeCl₃) P(O₂)

T(source) T(sink)

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Chemical Vapour Transport X.

Prerequisit for the application of the diffusion model:

Diffusion between source and sink is the rate determining step of the whole migration/deposition process

migration / deposition:

(mechanism)

1.) Reaction of ABK with transport agent 2.) evaporation of volatile species

(1. phase transfer reaction)

3.) “migration” from source to sink 4.) seed formation

5.) Crystal growth

(2. phase transfer reaction)

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Chemical Vapour Transport XI.

Transport formula derived by Harald Schäfer

 , [ ]

,

n i

j

P P

T q

s D mol

A

= ⋅

C

⋅ ⋅

⋅ ⋅ ⋅

⁻

∆ Σ

0 8

0

1 8 10

3

n_A i, j ∆P_c 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]

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Transport of Metals I.

Zr_s + 4 I_g = ZrI_4,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) Mo_s + 5/2 Cl_2,g (5 Cl_g) = MoCl_5,g; 400 1400°C

W_s + 3 Cl_2,g (6 Cl_g) = WCl_6,g; 400 1400°C

Ni_s + 4 CO_g = 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))

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Transport of Metals II.

e. g.: M_s + 2 Cl_g = MCl_2,g; 800 1000°C

Transport of Fe and Ni using halogens (exothermic):

thermal instability of halides, e. g.:

Rh_s + 3/2 Cl_2,g = RhCl_3,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.: M_s + 2 HCl_g = MCl_2,g + 2 H_2,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.:

Rh_s + 3/2 Cl_2,g + Al₂Cl_6,g = RhAl₂Cl_9,g; 600 800°C

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Transport of Oxides I.

Fe₂O_3,s + 3 Cl_2,g = 2 FeCl_3,g + 3/2 O_2,g; 1000 900°C Chlorine as transport agent:

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

TiO_2,s + 2 Cl_2,g = TiCl_4,g + 2 O_2,g; 900 800°C

MoO_3,s + Cl_2,g = MoO₂Cl_2,g + 1/2 O_2,g; 900 800°C

Nb₂O_5,s + 3 Cl_2,g = 2 NbOCl_3,g + 3/2 O_2,g; 1000 900°C

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

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Transport of Oxides II.

Fe₂O_3,s + 6 HCl_g = 2 FeCl_3,g + 3 H₂O_g; 900 800°C Non-oxidising transport agents:

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

Ti₃O_5,s + 12 HCl_g = 3 TiCl_4,g + 5 H₂O_g + H_2,g; 900 800°C MoO_3,s + TeCl_4,g = MoO₂Cl_2,g + TeOCl_2,g; 900 800°C

Ta₂O_5,s + 3 TaCl_5,g = 5 TaOCl_3,g; 1000 900°C 3 TiO_2,s + 4 PI_3,g = 3 TiI_4,g + P₄O_6,g; 900 800°C

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Transport of Complex Oxides I.

CoNb₂O_6,s + 5/2 Cl_2,g = CoCl_2,g + NbOCl_3,g + 5/2 O_2,g Transport behaviour similar to binary components:

lower solubility generally means lower solubility difference (lower migration rate)

(Co_1-xZn_x)O_s + Cl_2,g = (1-x) CoCl_2,g + x ZnCl_2,g + 1/2 O_2,g Stabilisation of binary componenten by formation of the ternary

phase leeds to lower solubility in the gas phase of the ternary phase in comparison to the binary phases.

NiTiO_3,s + 3 Cl_2,g = NiCl_2,g + TiCl_4,g + 3/2 O_2,g

(75)

Transport of Complex Oxides II.

ZnSO_4,s + Cl_2,g = ZnCl_2,g + SO_2,g + 1/2 O_2,g Chemical Vapour Transport of anhydrous sulfates:

Fe₂(SO₄)_3,s + 3 Cl_2,g = 2 FeCl_3,g + 3 SO_3,g + 3/2 O_2,g Fe₂(SO₄)_3,s + 3 Cl_2,g = 2 FeCl_3,g + 3 SO_2,g + 3 O_2,g FeSO_4,s + 2 HCl_g = FeCl_3,g + SO_2,g + H₂O_g + O_2,g

(formation of Fe₂O_3,s)

NiSO_4,s + Cl_2,g = NiCl_2,g + SO_3,g + 1/2 O_2,g Al₂(SO₄)_3,s + 3 SOCl_2,g = 2 AlCl_3,g + 6 SO_2,g

2 VO(SO₄)_s + 3 Cl_2,g = 2 VOCl_3,g + 2 SO_3,g + O_2,g

NiSO_4,s + PbCl_2,g = PbSO_4,s + 2 NiO_s + SO_2,g + Cl_2,g

(76)

Transport of Halides I.

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

CrCl_3,s + 1/2 Cl_2,g = CrCl_4,g; 800 700°C MoBr_3,s + MoBr_5,g = 2 MoBr_4,g; 475 250°C

Transport via higher halogenides (TR accompanied by oxidation):

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

MoBr_2,s + HgBr_2,g = MoBr_4,g; 1000 900°C

2 AlCl_3,g = Al₂Cl_6,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]

(77)

Transport of Halides II.

Dissoziation behaviour of Al₂Cl_6,g

(compare also dimerisation of CoCl_2,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]

Al₂Cl_6,g AlCl_3,g

(78)

Transport of Halides III.

(79)

Transport of Halides IV.

Examples (synthesis of crystaline, anhydrous halogenides):

2 CrCl_3,s + 3 Al₂Cl_6,g = 2 CrAl₃Cl_12,g

CoBr_2,s + Al₂Br_6,g = CoAl₂Br_8,g; 400 300°C

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

But:

CrCl_2,s + Al₂Cl_6,g = CrAl₂Cl_8,g; 450 350°C

Pt (excess) + Br_2,s + Al₂Br_6,g Y PtBr_3,g; 400 350°C

Pd (excess) + I_2,s + Al₂I_6,g Y Pd₂Al_s + I_2,g; T: 350 - 600°C Transport of Pd₂Al_s: 375 600°C

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

Linde A Ultramarin

Linde X/Y, Faujasit

Na₂Ca[Al₄Si₁₀O₂₈]·20H₂O 4

Sodalith β-Käfig

(85)

Ein molekularer Baukasten

(86)

Ein molekularer Baukasten

(87)

Löcher mit SiO ₂ drumherum

Linde A Linde X/Y, Faujasit

Na₂Ca[Al₄Si₁₀O₂₈]·20H₂O Sodalith

Zeolithe besitzen Hohlräume, in die Moleküle oder Ionen eingelagert werden können.

(88)

Synthese von Zeolithen

SiO

₂

haltige Verbindungen

z.B. Wassergläser, Kieselsole

+ Natronlauge, Temperatur > 50°C, hydrothermale Reaktionsbedingungen

Zeolith

Al

₂

O

₃

haltige Verbindungen

z.B. Aluminiumhydoxide, Aluminate, Kaoline

(89)

Anwendungen von Zeolithen

Eigenschaft Anwendung

Adsorption Isolierglas

Kühlmittel

Dynamische Adsorption Trocknung und Reinigung von Erdgas, Spaltgas; Luftzerlegung

Trenneigenschaften Alkane / Isoalkane Trennung,

Ionenaustausch Waschmittel, Abwasserreinigung

Katalyse Fließbettcracken, Hydrocracken,

Methanolumwandlung

(90)

Phosphates with Open Framework Structures

A. K. Cheetham, G. Férey, T. Loiseau, Angew. Chem. 1999,111, 3466-3492.

VPI-5 (AlPO₄)

M. E. Davis et al., Nature 1988,331, 698.

~13 Å

Precipitation in

the presence of

a structure dir-

ecting reagent

(91)

Phosphates with Open Framework Structures

A. K. Cheetham et al., Chem. Commun. 2001, 859-860.

VSB-1 [Ni₁₈(HPO₄)₁₄(OH)₃F₉(H₃O/NH₄)₄ • 12 H₂O

Effective catalyst for dehydrocyclodimerization of butadien!

Limited thermal stability of open framework

M. Blum, unpublished results, Univ. of Bonn, 2004.

H. Thauern, Diploma Thesis, Univ. of Bonn, 2002.

M₂(H₂P₂O₇)₂ = M₂P₄O₁₂ + 2 H₂O (M = Ni, Zn) 2 M₂(H₂P₂O₇)₂ = M(PO₃)₂ + 2 H₂O (M = Zn)

(93)

Various Forms of FePO ₄

c c

b c

b

c

b

(94)

94

Aufbau eines Li-Ionen Akkumulators

M. Wohlfahrt-Mehrens, Zentrum für Sonnenenergie- und Wasserstoff-Forschung, Ulm.

Laden Entladen

Flüssige od. feste (Polymer) Elektrolyte

Alternative Elektroden- materialien?

z.B.: LiFe^IIPO₄

Aufgeladen: Co^IVO₂ und LiC₆ Entladen: LiCo^IIIO₂ und C₆

Alternative Elektrolyte?

94

(95)

Various Forms of FePO ₄

A.S. Anderson, B. Kalska, L. Haggstrom, J. O. Thomas, Solid State Ionics 2000, 130, 41-52.

Delithiation of LiFePO

₄

(Olivine):

preservation of the kinetically stable network structure

a

b

mineralogy:

(Fe_1-xMn_x)PO₄ from Li(Fe_1-xMn_x)PO₄

new compounds:

V₂(PO₄)₃ from Li₃V₂(PO₄)₃

Lithium batteries;

electrode materials

Preparative Methods in Inorganic Solid State Chemistry