UNSPECIFIED. (2002) Investigation of the structure and phase transitions in the novel A-site substituted distorted perovskite compound Na0.5Bi0.5TiO3. ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE, 58 (Part 2). pp. 168-178. ISSN 0108-7681

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Abstract

Rietveld neutron powder profile analysis of the compound Na0.5Bi0.5TiO3 (NBT) is reported over the temperature range 5-873 K. The sequence of phase transitions from the high-temperature prototypic cubic structure (above 813 K), to one of tetragonal (673-773 K) and then rhombohedral structures (5-528 K) has been established. Coexisting tetragonal/cubic (773-813 K) and rhombohedral/tetragonal (with an upper temperature limit of 145 K between 528 and 673 K) phases have also been observed. Refinements have revealed that the rhombohedral phase, space group R3c, with a(H) = 5.4887 (2), c(H) = 13.5048 (8) Angstrom, V = 352.33 (3) Angstrom(3), Z = 6 and D-x = 5.99 Mg m(-3), exhibits an antiphase, a(-)a(-)a(-) oxygen tilt system, omega = 8.24 (4)degrees, with parallel cation displacements at room temperature. The tetragonal phase, space group P4bm, with a(T) = 5.5179 (2), c(T) = 3.9073 (2) Angstrom, V = 118.96 (1) Angstrom(3), Z = 2 and D-x = 5.91 Mg m(-3), possesses an unusual combination of in-phase, a(0)a(0)c(+) oxygen octahedra tilts, omega = 3.06 (2)degrees, and antiparallel cation displacements along the polar axis. General trends of cation displacements and the various deviations of the octahedral network from the prototypic cubic perovskite structure have been established and their systematic behaviour with temperature is reported. An investigation of phase transition behaviour using second harmonic generation (SHG) to establish the centrosymmetric or non-centrosymmetric nature of the various phases is also reported.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Journal or Publication Title:	ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE
Publisher:	BLACKWELL MUNKSGAARD
ISSN:	0108-7681
Date:	April 2002
Volume:	58
Number:	Part 2
Number of Pages:	11
Page Range:	pp. 168-178
Identification Number:	10.1107/S0108768101020845
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/11117

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