Raman spectroscopy of the LaGaO3 phase transition

LaGaO3 is reported to undergo a low-temperature phase transition from Pnma to R (3) over bar c at 418 K. The phases involved in the low-temperature phase transition of LaGaO3 were determined using Raman spectroscopy from 77 to 773 K. There is a total of 17 bands observed in the room temperature (294 K) Raman spectrum, namely, 55(A(g)), 92(B-1g), 101(B-3g), 117(B-2g), 137(B-1g), 147(A(g)), 173(B-3g), 255(A(g)), 277(A(g)), 335(B-3g), 357(B-1g), 404(B-3g), 417(B-2g), 433(A(g)), 451(B-3g), 584(overtone), 708(overtone) cm(-1) (at 294 K) and an extra band observed at 77 K of 331(B-2g) cm(-1). The Raman spectra of the rhombohedral LaGaO3 phase showed four distinct bands at 444(E-g/E-g), 232(A(g)), 159(E-g) and 55(E-g) cm(-1) (at 773 K) of a possible five predicted. The spectra of both the low-temperature orthorhombic and high-temperature rhombohedral phases of LaGaO3 phases were assigned with comparison with assignments of SmAlO3 and NdAlO3, respectively. The phase transition is observed to occur at approximately 418 K. Copyright (C) 1999 John Whey & Sons, Ltd.