Open AccessLattice parameters and structural phase transition of lanthanum titanate perovskite, La 0.68 (Ti 0.95 ,Al 0.05 )O 3
Author(s) -
Ali Roushown,
Yashima Masatomo
Publication year - 2003
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049503002504
Subject(s) - tetragonal crystal system , orthorhombic crystal system , phase transition , materials science , crystallography , lattice constant , synchrotron radiation , lattice (music) , x ray crystallography , landau theory , diffraction , condensed matter physics , analytical chemistry (journal) , crystal structure , chemistry , physics , optics , acoustics , chromatography
Lattice parameters and the structural phase transition of La 0.68 (Ti 0.95 ,Al 0.05 )O 3 have been investigated in situ in the temperature range 301–689 K by the synchrotron radiation powder diffraction (SR‐PD) technique. High‐angular‐resolution SR‐PD is confirmed to be a powerful technique for determining precise lattice parameters around a phase‐transition temperature. The title compound exhibits a reversible phase transition between orthorhombic and tetragonal phases at 622.3 ± 0.6 K. The following results were obtained: (i) the lattice parameters increased continuously with temperature, while the b / a ratio decreased continuously with temperature and became unity at the orthorhombic–tetragonal transition point; (ii) no hysteresis was observed between the lattice‐parameter values measured on heating and on cooling. Results (i) and (ii) indicate that the orthorhombic–tetragonal phase transition is continuous and reversible. The b / a ratio is found to exhibit a more continuous temperature evolution than does the order parameter for a typical second‐order phase transition based on Landau theory.