Photoluminescence study of cadmium tungstate crystals Original Research Article

The steady-state luminescence properties of bismuth-doped and undoped CdWO4 crystals have been investigated at temperatures ranging from 4.8 to 320 K. Three different excitation wavelengths (313, 325 and 351 nm) were used. The intrinsic “blue” emission band (near 490 nm at room temperature) was observed in both undoped and Bi-doped CdWO4 crystals when pumped with above-band-gap light. When excited with 351-nm below-band-gap light at room temperature, the undoped sample exhibited no significant emission while the Bi-doped sample exhibited a bright yellow emission near 560 nm due to transitions within the Bi3+ ions. The peak position and integrated intensity of both emission bands were monitored as a function of temperature from 5 to 320 K. Also, the polarization dependence was determined for the Bi-related emission and the intrinsic emission in CdWO4. The yellow PL from Bi3+ ions and its associated absorption band peaking near 350 nm were found to be partially polarized (i.e. enhanced when the electric field is oriented perpendicular to the b-axis of the crystal).