A structural study of the perovskite series Na{sub 1/2+x}La{sub 1/2{minus}3x}Th{sub 2x}TiO{sub 3}

Journal Article · Wed Jul 01 04:00:00 EDT 1998 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1998.7789· OSTI ID:651125

Mitchell, R H; Chakhmouradian, A R ^[1]

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1. Lakehead Univ., Thunder Bay, Ontario (Canada). Dept. of Geology

An X-ray powder diffraction study of the series Na{sub 1/2+x}La{sub 1/2{minus}3x}Th{sub 2x}TiO{sub 3} is presented. The series comprises orthorhombic CaTiO{sub 3}-type perovskites (Pnma, a {approx} c {approx} {radical}2a{sub p}, b {approx} 2a{sub p}) in the range 0 {le} x {le} 0.083 and tetragonal La{sub 1/2}Li{sub 1/2}TiO{sub 3}-type perovskites (P4/mmm, a = a{sub p}, c {approx} 2a{sub p}) in the range 0.100 {le} x {le} 0.167. The structure of the orthorhombic members is derived from the cubic aristotype by octahedral rotation. The degree of octahedral rotation is relatively small ({Phi} = 4.1--7.6{degree}), compared to that of other CaTiO{sub 3}-type perovskites. The tetragonal members of the series exhibit partial ordering of the cations at the A-site: the 1a and 1b sites are preferentially occupied by Na and Th, respectively. This results in alternate layers of Na and Th atoms perpendicular to the c axis of the tetragonal cell. Ti atoms are displaced from the center of the TiO{sub 6} polyhedra due to the strong electrostatic repulsion effect of Th and La at the A-site. In contrast to previous studies, the end-member Na{sub 2/3}Th{sub 1/3}TiO{sub 3} is shown not to have a cubic cell.

• OSTI ID: 651125
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 138; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRYSTAL STRUCTURE
EXPERIMENTAL DATA
LANTHANUM OXIDES
LATTICE PARAMETERS
PEROVSKITE
SODIUM OXIDES
SOLUBILITY
THORIUM OXIDES
TITANIUM OXIDES
X-RAY DIFFRACTION