The frequency shift of the Raman modes in strontium tungstate (SrWO₄) was investigated in the temperature range from 15 to 295 K. The experimental temperature dependence of the shift was analyzed using both the lattice dynamical calculations and the lattice perturbative approach. We found that the quartic anharmonic term of the first-order perturbation and the cubic term of the second-order perturbation, as well as the thermal expansion, contribute to the temperature shift of the highest-frequency A_g(ν₁) mode. The values of the temperature sensitivity of the frequency shift of the Raman modes at room temperature were measured, which is important for developing high-power crystalline Raman lasers and frequency shifters.

Raman spectra for longitudinal optical phonon-plasmon coupled mode in n-type GaN crystals were measured from room temperature to 200 °C by micro-Raman spectroscopy. We calculated the electron density, electron mobility, and resistivity values of the sample by spectra analysis fitting of the imaginary part of the dielectric dispersion equation to this observed mode profiles using adjustable parameters in n-type GaN at high temperatures. The calculated values of the electron density, electron mobility, and resistivity reproduced those by Hall effect measurement. The results showed that the electron density values in n-type GaN tend to increase slightly with increasing temperature while the electric mobility decreases.