High-temperature, high-pressure Raman spectra and their intrinsic anharmonic effects in the perovskite Pb1-xLaxTiO3

Raman spectra of ferroelectric Pb1-xLaxTiO3, in the tetragonal phase of the material and for different La concentrations, were studied for different temperatures and pressures. While temperature was varied from 8 K to transition temperature (T-c) at atmospheric pressure, applied hydrostatic pressure was increased from zero to transition pressure (P-c) at room temperature. Isobaric and isothermal mode-Gruneisen parameters were calculated from the measured Raman spectra, and previously reported coefficients of thermal expansion [Chen et al., J. Am. Ceram. Soc. 88, 1356 (2005)] and bulk moduli. Also the coefficient of intrinsic anharmonicity was calculated. Although the absolute value of Gruneisen parameters strongly depends on the Raman mode under study, all of them grow as La concentration increases. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772721]