STRUCTURE, THERMAL EXPANSION AND PHASE TRANSITION IN La_(0.92)Sr_(0.08)Ga_(0.92)Ti_(0.08)O_3 SINGLE CRYSTAL

摘要

The structure of mixed La_(0.92)Sr_(0.08)Ga_(0.92)Ti_(0.08)O_3 (LSGT-8) single crystal, obtained by Czochralsky method, have been investigated in a wide temperature range of 12-1203 K by means of in situ high resolution powder diffraction technique using synchrotron radiation as well as DTA/DSC analysis. Both, diffraction and calorimetric data indicate a first-order phase transition from orthorhombic (space group Pbnm) to rhombohedral (space group R-3c) structure near the room temperature (T_c ≈ 303 K). Lattice parameters and atomic coordinates of low- and high-temperature phases have been refined in the whole temperature range investigated. It was established that the critical temperature of the phase transition in the system (1-x)LaGaO_3-(x)SrTiO_3 in the concentration range of x = 0/(0.08) falls down linearly according to the empirical relation: T_c ≈ 419(9)-15.4(17)~*x.