Hydroxyl ion absorption in LaGaO3 single crystals Original Research Article

LaGaO3 single crystals have been studied by means of Fourier transform infrared (FTIR) absorption spectroscopy in the range of OH−/OD− stretching vibrations. A single narrow absorption line has been detected at low temperatures down to T=9 K in most of the as grown crystals at about 3521 cm−1. An abrupt decrease of the vibrational frequency has been observed at the orthorhombic–rhombohedral structural phase transition temperature (Tc=418 K). The temperature dependence of the frequency and the linewidth of the absorption line below the phase transition have been analysed by using the single phonon-coupling model. The parameters of the anharmonic potential of the OH− stretching vibration have been determined by three different methods (xe=0.02272 and as calculated from the second harmonic) and found to be in agreement with those measured for hydroxyl ions in other oxide crystals. Additional OH−/OD− absorption lines have been detected in a few LaGaO3 crystals treated in H2O/D2O vapours.