CdWO4 Crystal: Thermal Expansion Coefficients, High-Temperature Photoluminescence

High-temperature properties of the CdWO₄ cadmium tungstate crystal are studied. This crystal has broad practical applications, e.g. as a scintillator, due to its optical and radiative properties. CdWO₄ preserves high structural stability up to 1150 °C and begins to decompose at 1200 °C. Crystal lattice parameters and thermal expansion coefficients are calculated. The latter exhibit the largest expansion along the b axis. High transmittance of the studied sample in the ~0.32-5.0 µm range confirms high optical quality of the crystal and its prospects in photonic applications. The photoluminescence study in the 23-200 °C range reveals two types of luminescence transitions E1 and E2 and shows that the intensity of the spectrum decreases with increasing temperature and vanishes at 200 °C. It is shown that the tendency of intensity decrease depends on the excitation wavelength.