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Structural Behavior and Raman Spectra of Perovskite-Like Solid Solutions (1-x)LaMg0.5Ti0.5O3-xLa2/3TiO^d3



Igor Levin, Terrell A. Vanderah, T Amos, James E. Maslar


Structural behavior and phase transitions in the A-cation deficient perovskite-like solid solutions (1-x)LaMg0.5Ti0.5O3-xLa2/3TiO3 (0=x=0.5) were studied using variable-temperature transmission electron microscopy (TEM) and X-ray powder diffraction combined with ambient temperature neutron powder diffraction measurements. These solid solutions feature a series of octahedral-tilting phase transitions and a B-site Mg/Ti order-disorder phase transition; the temperatures of these transitions decreased with increasing x. Additionally, short-range ordering of A-site vacancies was detected for x>0.40 using high-resolution TEM. A phase diagram summarizing ordering and displacive phase transitions was determined from variable-temperature diffraction and imaging experiments. Among the tilting transitions, a relatively uncommon first-order phase transition between structures exhibiting orthorhombic (a+b-b- and a0b-c-) and rhombohedral (a-a-a-) tilt systems was observed; the rhombohedral tilt was stabilized at room temperature for x=0.50. Raman spectra of the solid solutions revealed anomalous asymmetric broadening of certain peaks associated with B-site ordering. This broadening, which occurred even for the samples exhibiting significant long-range Mg/Ti order and large anti-phase ordered domains, was attributed to phonon confinement effects caused by strong heterogeneity of the B-site order parameter within each anti-phase domain.
Chemistry of Materials


crystal structures, perovskites, phase transitions, Raman spectra


Levin, I. , Vanderah, T. , Amos, T. and Maslar, J. (2005), Structural Behavior and Raman Spectra of Perovskite-Like Solid Solutions (1-x)LaMg<sub>0.5</sub>Ti<sub>0.5</sub>O<sub>3-x</sub>La<sub>2/3</sub>TiO^d3, Chemistry of Materials, [online], (Accessed February 24, 2024)
Created June 14, 2005, Updated February 19, 2017