Bi1−xCrxO1.5+1.5x′, 0.05≤x≤0.15: A New High-Temperature Solid Solution with a Three-Dimensional Incommensurate Modulation

✍ Scribed by S. Esmaeilzadeh; S. Lundgren; U. Hålenius; J. Grins

• Book ID: 102974932
• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 655 KB
• Volume: 156
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8978

✦ Synopsis

A new metastable solid solution Bi 1؊x Cr x O 1.5؉1.5x with 0.054x40.15 was synthesized by quenching Bi+Cr+O melts and structurally investigated using electron microscopy and Xray di4raction. The oxidation state of Cr was determined to be ؉ VI by thermogravimetry, optical spectroscopy, and magnetic measurements. Infrared spectra indicate for x ‫؍‬ 0.05 isolated CrO 2؊ 4 tetrahedra and also smaller fractions of Cr 2 O 2؊ 7 units. The phase exhibits an average structure of the Fm3 m 6uorite type and a 3D incommensurate modulation, with wave vectors q 1 ‫؍‬ [ , 0, 0]*, q 2 ‫؍‬ [0, , 0]*, q 3 ‫؍‬ [0, 0, ]*, a ‫؍‬ 5.6025(3) A s , and ‫؍‬ 0.2866(2) for x ‫؍‬ 0.15, and with the 3 ؉ 3D superspace group symmetry P:Fm3 m:Fm3 m. Atomic modulation functions and periodic nodal surfaces were deduced for observed satellite re6ections and a commensurate structure model derived for x ‫؍‬ 0.05. The modulated structure was compared with that of Bi 0.78 Nb 0.22 O 1.72 , with symmetry P:Fm3 m:Fd3 m.