Raman studies of LaGaO3 and doped LaGaO3

LaGaO3 and LaGaO3 doped with various amounts of Sr and Mg were prepared using the solid-state reaction method. Room temperature Raman spectra of the compounds exhibited a striking decrease in the number of bands on doping either B site only, or both A and B sites of the Perovskite structure, as compared with undoped LaGaO3. This phenomenon indicates that the doping enhanced the symmetry of the crystal structure. In addition, the spectra of all doped compounds showed new Raman bands at around 700 cm(-1), probably due to local symmetry decrease, caused by the oxygen vacancy induced by doping. Raman spectra at elevated temperatures revealed that some LaGaO3 doped at both A and B sites became almost cubic structure at 1000 degrees C. Electrical conductivity was also measured, which is considered to be related to the long- and short-range symmetry changes observed with Raman spectra. (C) 1999 Elsevier Science B.V. All rights reserved.