Structure and chemistry of Ba sub 0. 6 K sub 0. 4 BiO sub y at high temperature

Journal Article · Thu Oct 31 23:00:00 EST 1991 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1016/0022-4596(91)90373-P· OSTI ID:7265780

Pei, Shiyou; Richards, D R; Dabrowski, B; Jorgensen, J D; Hinks, D G; Zheng, Ying; Mitchell, A W ^[1]

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1. Argonne National Lab., IL (United States)

A combination of neutron powder diffraction and thermogravimetric analysis has been used to study the structural phase behavior of Ba{sub 1{minus}x}K{sub x}BiO{sub y} under conditions that simulate synthesis. On heating in 1% O{sub 2}, the cubic perovskite Ba{sub 0.6}K{sub 0.4}BiO{sub 3} decomposes to a mixture of Ba{sub 1{minus}x}K{sub x}BiO{sub y} with x < 0.4 and KBiO{sub 2}. Further increase in temperature causes the reincorporation of potassium into the perovskite at the expense of KBiO{sub 2}. At 720 C, the sample is again a single-phase cubic perovskite with x = 0.4 containing a large concentration of oxygen vacancies. If this sample is then cooled in argon, no chemical phase decomposition occurs. Instead, the cubic oxygen-deficient perovskite transforms to an orthorhombic oxygen-vacancy-ordered phase. A subsequent low-temperature anneal in pure oxygen fills the oxygen vacancies while retaining the potassium in the lattice, resulting in a transformation back to the cubic perovskite. This work shows that fully oxygenated Ba{sub 1{minus}x}K{sub x}BiO{sub 3} for x > 0.1, including the superconducting compositions, is metastable, and supports the hypothesis that the creation of oxygen vacancies is necessary to allow the substitution of K{sup 1+} for Ba{sup 2+} in the lattice.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 7265780
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 95:1; ISSN 0022-4596; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602 -- Other Materials-- Structure &amp; Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ANNEALING
ATMOSPHERES
BRAGG CURVE
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
CHEMISTRY
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
DIAGRAMS
DIFFRACTION
ELEMENTS
GRAVIMETRIC ANALYSIS
HEAT TREATMENTS
MINERALS
MOLECULAR STRUCTURE
NEUTRON DIFFRACTION
NEUTRON SOURCES
NONMETALS
ORTHORHOMBIC LATTICES
OXIDE MINERALS
OXYGEN
PARTICLE SOURCES
PEROVSKITE
PEROVSKITES
POWDERS
QUANTITATIVE CHEMICAL ANALYSIS
RADIATION SOURCES
SCATTERING
STRUCTURE FACTORS
SUPERCONDUCTORS
SYNTHESIS
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
THERMAL ANALYSIS
THERMAL DEGRADATION
THERMAL GRAVIMETRIC ANALYSIS