Perovskite-type Ca{sub 1{minus}x}Sr{sub x}NbO{sub 3} (0 {le} x {le} 1) phases: A synthesis, structure, and electron microscopy study
Journal Article
·
· Journal of Solid State Chemistry
- Moscow State Univ. (Russian Federation). Chemical Dept.
- Stockholm Univ. (Sweden)
- Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid State Physics
Reduced niobates Ca{sub 1{minus}x}Sr{sub x}NbO{sub 3} (0 {le} x {le} 1) with perovskite-type structures have been synthesized at 1500 C in niobium ampoules sealed under argon gas. The prepared compounds were characterized by X-ray powder diffraction, electron diffraction, high-resolution electron microscopy, and energy-dispersive X-ray analysis. The structure of CaNbO{sub 3} (GdFeO{sub 3} type) was refined using X-ray powder diffraction data. Electron diffraction studies showed that complex superstructures of the perovskite-type structure occur for x > 0 in Ca{sub 1{minus}x}Sr{sub x}NbO{sub 3}: (i) for x = 0.2 and 0.3 reflections corresponding to a supercell with a {approx} 2 {times} {radical}2 {times} a{sub per}, b {approx} 4 {times} a{sub per}, and c {approx} 2 {times} {radical}2 {times} a{sub per} (per = ideal perovskite) were observed, (ii) for x = 0.5, 0.6, and 0.7 a cubic supercell was found with a = 4 {times} a{sub per} whereas (iii) for x = 0.8 and 0.9 the supercell is probably orthorhombic with a {approx} c {approx} {radical}2 {times} a{sub per} and b {approx} 2 {times} a{sub per}. For x = 1.0 a new orthorhombic modification of SrNbO{sub 3} with a {approx} c {approx} {radical}2 {times} a{sub per} and b {approx} 2 {times} a{sub per} was found. Resistivity measurements showed CaNbO{sub 3} to have a nonmetallic type of conductivity, whereas the Sr-containing samples were metallic.
- OSTI ID:
- 329156
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 141; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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