Photoluminescence and photoconductivity studies on NaBi(WO4)2 single crystals: A promising Cherenkov radiator

Results of photoluminescence in conjunction with photoconductivity properties of NaBi(WO4)2 crystal are presented and explained with the help of calculated electronic and optical properties. Crystals were annealed in air/vacuum to change the local environment near (WO4)2− complex and consequently two emission bands near 470 and 520 nm could be separated for excitation at different energies. The activation energy for thermal quenching of emission was calculated to be 160 meV. The role of excitons and localization of charge carriers is explained on the basis of photoconductivity of these crystals that has been observed only intrinsically in contrast to iso-structurally PbWO4.