Title: Studies of Oxygen Deficient Complex Cobaltates with Perovskite Related Structures
1Studies of Oxygen Deficient Complex Cobaltates
with Perovskite Related Structures
- Doctoral Thesis
- Fredrik Lindberg
2Contents
- Its a perovskite material world
- Where are (or where are not) the oxygens
- Based on what?
- Summary
- Acknowledgements
3Its a perovskite material world
ABX3
The perovskite structure.
4Its a perovskite material world
t lt 1superstructures
t gt 1hexagonal variants
t 1cubic, ideal
The toleranced factor for perovskites
5Its a perovskite material world
Important properties
6Its a perovskite material world
Spin state transitions in coboltates
LS
IS
HS
LaCoO3 (P.G. Radaelli et. al. Phys. Rev. B66
(2002) 094408)
Magnetism
7Its a perovskite material world
Superexchange Anti-Ferromagnetism
Co3
Co3
Double-exchange - Ferromagnetism
Co3
Co4
Co3
Co4
Magnetism
8Where are (or where are not) the oxygens
Oxygen deficiency
SrFeO3
Sr4Fe4O11
Sr2Fe2O5
Sr8Fe8O23
Homologous serie, AnBnO3n-1
Deficiency
(J.P. Hodges et. al. JSSC. 151, (2000) 190)
9Where are (or where are not) the oxygens
The Brownmillerite structure
10Where are (or where are not) the oxygens
The Brownmillerite structure
11Where are (or where are not) the oxygens
Pcmn
Ibm2
Icmm
The Brownmillerite structure
12Where are (or where are not) the oxygens
Icmm
Ibm2
Pcmn
The Brownmillerite structure
13Where are (or where are not) the oxygens
314 - phase
14Based on What?
Stabilise Brownmillerite Sr2Co2O5 by aliovalent
doping
Paper I Synthesis and structural studies of
Sr2Co2-xGaxO5, 0.3 x 0.8
Paper II Synthesis and structural studies of
Sr2Co2-xAlxO5, 0.3 x 0.5
Paper I and II
15Based on What?
Sr2Co2-xGaxO5
100
001
Paper I
16Based on What?
Sr2Co1.7Ga0.3O5
Paper I
17Based on What?
Sr2Co1.7Ga0.3O5
Co3oct 2.8BM Co3tetr 2.5BM
IS 3BM
LS 0BM
Paper I
18Based on What?
Sr1-xLnxCoO3-? 314-phase at x 0.3, Ln Y, Eu-Ho
Paper III Influence of Oxygen Defects on the
Structure and Magnetic Properties of
Sr1-xBixCoO3-y (0.1 x 0.2) Supercell
Perovskites.
Paper IV Synthesis and characterization of
Sr0.75Y0.25Co1-xMxO2.625? (M Ga, 0.125 x
0.500 and M Fe, 0.125 x 0.875),
Paper III IV
19Based on What?
Sr1-xBixCoO3-y 314-phase for x 0.1 0.2
Sr0.75Y0.25Co1-xMxO2.625? 314-phase x 0.375
(M Ga) x 0.625 (M Fe)
Paper III IV
20Based on What?
Paper IV
Paper IV, page 1439
21Based on What?
TGA in O2
Sr1-xBixCoO3-y
Sr0.7Y0.3CoO2.62 (Istomin et al. Chem. Mater.
15, 4012)
x
8
0
6
0
0.10
4
2
0
-60
4
0
1
0.20
2
-5
200
1000
600
400
800
0
T/?C
-80
Paper III
200
800
400
600
T/?C
22Based on What?
Chemically induced AFM FM transitions,
Sr1-xBixCoO3-y
Sr0.85Bi0.15CoO2.9
Sr0.85Bi0.15CoO2.7
Paper III
23Summary
Brownmillerites Sr2Co2-xGaxO5 and
Sr2Co2-xAlxO5 Domain structure, AFM, IS Co3.
314 structure Sr0.75Y0.25Co1-xGaxO2.625 and
Sr0.75Y0.25Co1-xFexO2.625. Domain structure and
well ordered, FM from spin-canting, FM domains.
Sr1-xBixCoO3-y O2 uptake, 314 to cubic AFM FM
transition. FM due to Co3-Co4 double exchange..
24Acknowledgements
- Sergey Istomin and Oleg Drozhzhin, Moscow State
University. - Christopher Knee, Chalmers/Gothenburg University.
- Peter Warnicke and Peter Svedlindh Uppsala
University.
25Its a perovskite material world
The toleranced factor for perovskites
26Its a perovskite material world
The toleranced factor for perovskites
27Its a perovskite material world
Double exchange
Magnetism
28Based on What?
Paper III IV
29Its a perovskite material world
Chemically induced AFM FM transitions,
Sr2/3Y1/3CoOx
Ferromagnetic domains to small to be detected by
NPD
Magnetism
A. Maignan et. al. J. Solid State Chem. 178
(2005) 868
30Its a perovskite material world
B Metall d
Oxygen p
SrTiO3
LaNiO3, LaCuO3
Important properties
31Where are (or where are not) the oxygens
Ba2In2O5 (K.R. Kendall et. al. Solid State Ionics
82 (1995) 215-223)
32Where are (or where are not) the oxygens
The Brownmillerite structure
The Brownmillerite structure
33Based on What?
Paper I
34Its a perovskite material world
The toleranced factor for perovskites
35Based on What?
Sr2Co1.5Al0.5O5
Page 19 in thesis
Paper II