X-ray study of crystal structure and diffuse scattering spectra of ferroelectric SbSBr having pseudo-Jahn–Teller phase transition

• Published in: The Journal of physics and chemistry of solids Vol. 60; no. 5; pp. 587 - 598
• Main Author: Inushima, Takashi
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.1999; Elsevier
• Subjects: A. semiconductor; Anharmonic lattice modes; C. X-ray diffraction; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; D. crystal structure; D. ferroelectricity; D. phase transition; Exact sciences and technology; Lattice dynamics; Phonons and vibrations in crystal lattices; Physics; Structure of solids and liquids; crystallography; A. semiconductor; D. crystal structure; D. ferroelectricity; D. phase transition; C. X-ray diffraction; Temperature dependence; Inorganic compounds; Phase transformations; Ternary compounds; Antimony bromides; Experimental study; Jahn-Teller effect; Diffuse scattering; Antimony sulfides; X-ray scattering; Unit cell; Ferroelectric materials; Anharmonicity; One-dimensional systems; Crystal structure
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/S0022-3697(98)00321-7

The crystal structure of ferroelectric SbSBr was determined at 294, 150, 60, 30 and 11 K and a phase transition was observed to occur at T c=22.8 K, where the crystal structure changed from orthorhombic Pnam with z=4 to orthorhombic Pna2 1 with z=4. The unit cell volume decreased from 0.316 nm 3 (294 K) to 0.310 nm 3 ( T c) and increased to 0.312 nm 3 (11 K) below T c and there was a drastic decrease of the volume near T c. The diffuse X-ray scattering spectra of the (0 0 4) Bragg spot indicated that SbSBr had a quasi-one dimensional structure and when the temperature decreased to T c, the interaction between the chains became strong in the a*-direction in addition to in the b*-direction. The temperature dependence of the unit cell volume was regarded to be due to two B lu modes, which contributed as anharmonic vibrations to stabilizing the paraelectric phase in the pseudo-Jahn–Teller mechanism. It was concluded that the decrease of the anharmonicity of the low frequency B lu mode induced a drastic decrease of the unit cell volume below 30 K, and produced long range interaction causing the phase transition to occur at 22.8 K.