h. giefers, universität paderborn einleitung hochdruck-kristallographie und synthese 28. august...

H. Giefers, Universität Paderborn

Einleitung

Hochdruck-Kristallographie und Synthese28. August 2003

Reaktionskinetik der Disproportionierung von SnO unter Druck

Hubertus Giefers

Universität PaderbornDepartment Physik

AG Wortmann


Survey

1. The system tin – oxide

2. The disproportionation of SnO at ambient pressure- set up- analysis of the spectra

3. The disproportionation of SnO under pressure

4. Summary

5. Acknowledgement


1. The system tin and tin oxide

Sn SnO Sn2O3 SnO2

thermodyn. stable

thermodyn.

metastablethermodyn.

metastablethermodyn.

stable

7.31 g/cm³ 6.4 g/cm³ 7.03 g/cm³5.9 g/cm³

0 - 10 GPabct Sn-I

10 - 45 GPa bct Sn-II

45 - >120 GPabcc Sn-III

under hydrostaticpressure tetragonal

-PbOat least to 60 GPa

under nonhydrostatic compression orthorhombic

splitting

triclinic structure

a phase transition

at ca. 9 GPato unkown

structure

two low pressure phases:

tetragonal and orthorhombic

high pressure phase (>10 GPa)

fcc


1. The system tin and tin oxyde under pressure

our high pressurestudy on:

SnO to 50 GPatetragonal + orth. splittingz(Sn) was determined with EXAFS

Sn2O3 to 30 GPatriclinic, unkown

SnO2 to 50 GPatetragonal, orthorhomic,cubic

0 5 10 15 20 25 30 35 40 45 50 550.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

snoz_p.opj

p (GPa)

V/V

0

Sn-I + Sn-II (bct) SnO (st) SnO

x (triclinic)

SnO2 (st)


2. Disproportionation of SnO at ambient pressure

SnO

Sn2O3 + Sn

SnO2 + Sn

T > ca. 250 °C

SnO is metastable and disproportionates to the 2 stablematerials SnO2 and Sn at elevated temperatures.

Depending on temperature and alsoon the synthesis condition of SnO, the metastable compound Sn2O3 is formed in the disproportionation reaction, which decomposes to SnO2 and Snat higher temperature.



The disproportionation of SnO was studied ex situ and in situ withEnergy Dispersive X-Ray Diffraction (EDXRD) at beamline F3 at HASYLAB/DESY in Hamburg.

2



←heating band

ceramic spacer →

collimator ↓

HP cell →←thermocouple

↓ Al foil



irradiated SnO at 131 °C & 0 GPa after 15 h

GasketSnOdecomposed SnO(shape of SR beam)

Sample environment

0.2 mm


25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 300 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 3000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 6000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 9000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 12000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 15000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 18000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 21000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 24000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 27000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 30000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 33000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 36000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 39000 s

Inte

nsity

Energy (keV)25 30 35 40 45 50 55 60 65

SnO T = 370 °C

t = 42000 s

Inte

nsity

Energy (keV)


We analysed the normalized diffractionline intensities of the 3 samples SnO, Sn2O3

and SnO2. Sn was liquid or showed no reproducibleline intensities.

We used the fluoreszence lines of Sn to normalize the bragg peaks. This is an advantage of EDXRD. A time resolution of 100 s was achieved.


0 5000 10000 15000 20000 25000 30000 350000.0

0.2

0.4

0.6

0.8

1.0

1.2

T = 297 °C

Yie

ld fr

actio

n

Time (s)0 10000 20000 30000 40000

0.0

0.2

0.4

0.6

0.8

1.0

1.2

T = 370 °C

SnO SnO

2

SnOx

Yie

ld fr

actio

n

Time (s)


At low T (< 250 °C) SnOdecomposes due to the synchrotron radiation(!) tonanocrystalline SnO2 and Sn.

No Sn2O3 is produced.

At high T (>370 °C) the reaction is dominated by thermal disproportionation.

Sn2O3 is produced.



5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

avramib.opj

= 0.2 .. 0.63 from SnO

2+Sn

2O

3

ln( t(s) )

in °C 434 434 425 416 407 388 370 333 296 268 241 186 131

5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

= 0.2 .. 0.63 from SnO

SnO

Avrami-Erofe'ev Plot

ln(-

ln(1

-))

ln( t(s) )

Sharp-Hancock plot of the reaction progress


„activation energy EA“ radiation induced range : 27(2) kJ/molthermal induced range: 225(32) kJ/mol

Arrhenius:k = A exp(-EA/RT)


0 50 100 150 200 250 300 350 400 450 5000.4

0.8

1.2

1.6

2.0

2.4

avramib.opj

A2 : Avrami-Erofe'evF0 : Reaktionskinetik 0. OrdnungF1 : Reaktionskinetik 1. Ordnung D2 : 2D Diffusion (Zylinder)D3 : 3D Diffusion (Kugel)

A2

F0

F1

D2D3

Avrami-Erofe'evSnO, SnO2, Sn2O3

ln(-ln(1-)) = C + m*ln(t)mit C = m*ln(k) = 0.2 .. 0.63

m

Temperature (°C)0.00016 0.00018 0.00020 0.00022 0.00024 0.00026

-12

-10

-8

-6

-4

avramib.opj

Disproportionation of SnO from SnO and Sn

2O

3 + SnO

2 radiation induced thermal induced

EA,r

= 25(7) kJ/molln(A

r) = -6.0(2)

EA,t

= 166(19) kJ/molln(A

t) = 21(3)

359 °C

1/RT (mol/J)

ln( k(

s-1)

)

450 400 350 300 250 200

Temperature (°C)

1E-5

1E-4

1E-3

0.01

k (s-1)

- up to ca. 275 °C the in situ reaction is radiation induced- above 370 °C the in situ reaction is mainly thermal induced



t = 180 s t = 615 s t = 825 s t =1020 s t =1220 s t =1425 s t =1620 s

- at beamline F3 it is possible to do angle dispersive XRD (ADXRD) - the CCD camera is from GeoForschungsZentrum Potsdam with a time resolution of 150 s per frame- one test measurement was carried out at ambient pressure in the HP cell


0 500 1000 1500 20000.0

0.2

0.4

0.6

0.8

1.0

SnO fromAldrich

time (s)

yie

ld fr

act

ion

0.0

0.2

0.4

0.6

0.8

1.0

kinetik.opj

SnO fromChemPur

yie

ld fr

actio

n

SnO SnO

2


ADXRD kinetic study on the disproportionation of SnOwith 2 different SnO samples in the HP cell at 434 °C


3. Disproportionation of SnO at high pressure

Reaction kinetics under pressure

- high pressure cell made of a Ti-alloy- temperatures up to 500 °C can be reached- temperature at sample position was calibrated by the melting points of Pb, Sn, Zn- diamond flats of 1 mm and 0.5 mm were used- pressures of 20 GPa were reached- NaCl or MgO for pressure determination (Au was alloyed with Sn) - lN2 as pressure transmitting medium


0 2000 40000.0

0.2

0.4

0.6

0.8

1.0

1.2p = 3.3 GPa T = 296 °C

Time (s)

Yie

ld f

ract

ion

SnO SnO

2

0 2000 4000

p = 5.8 GPa T = 296 °C

Time (s)

under pressure:- no nanocrystalline SnO2 and Sn at low T- no radiation induced disproportionation- no production of Sn2O3 under pressure due to the low crystallographic density


some examplesunder pressure



Sharp-Hancock plot of

tmkm

emtk

lnln1lnln

1

m: reaction exponentk: reaction rate: reaction progress

5 6 7 8 9 10 11-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0SnO

2

p(GPa) / T(°C) 2.4/232 3.1/241 4.8/241 5.4/241 5.8/241 8.0/241 8.0/241 4.9/269 2.3/296 3.3/296 3.3/296 4.9/296 5.8/296 5.8/296 6.4/296 11.0/296 14.8/296 3.0/324 3.6/324 2.2/370

ln(-

ln(1

-))

ln(t (s))



- the reaction kinetic changes strongly under pressure

- the reaction exponent m is very low at 3 GPa

- in the measured p,T range the reaction exponent m is T independent

reaction exponent m:diffusion m ≈ 0.5phase-boundary ≈ 1nucleation and growth ≈ 2

rad

iatio

nin

duc

ed

0 2 4 6 8 10 12 14 160 .0

0 .2

0 .4

0 .6

0 .8

1 .0

1 .2

1 .4

1 .6

1 .8 = 1 - exp (-( k·t ) m ) = 0 .2 .. 0 .63

425 °C 370 °C 324 °C 296 °C 269 °C 241 °C 232 °C

m

p (G P a)


The reaction rate k of the disproportionation of SnO depends onthe phase of metallic Sn (liquid, Sn-I, Sn-II).


0 2 4 6 8 10 12 14 16

-13

-12

-11

-10

-9

-8

-7

-6

-5 liqu id -S n

S n-II

S n -I

p (G P a)

ln(k

(s-1

))

425 °C 400 °C 370 °C 350 °C 324 °C 296 °C 269 °C 241 °C 232 °C open: ex s itu

1E -5

1E -4

1E -3

k(s

-1)


4. Summary

- EDXRD provides a tool to study reaction kinetics in situ even at high pressure

- results are: reaction rates k and reaction mechanism m (nucleation, growth…)

the existence of intermediate products or not (Sn2O3)

the formation of high pressure phases at lower pressure (here SnO2-fcc)


- Felix Porsch: EDXRD Messungen

- H.-D. Niggemeier: ex situ Proben

-Ulrich Ponkratz: ADXRD Messungen

5. Acknowledgement

h. giefers, universität paderborn einleitung hochdruck-kristallographie und synthese 28. august...

Documents

sn sno

disproportionation of

ambient pressure sno

unkown sno

samples sno

nanocrystalline sno

stable materials sno

synthesis condition