Growth and scintillation properties of doped ZnWO4 crystals

A series of ZnWO4 crystals with different purities of WO3 and ZnO were grown by conventional Czochralski method and compared with Fe:ZnWO4, Nb:ZnWO4, Ag:ZnWO4 and Ce:ZnWO4 crystals grown by the same technology. Scintillation experiments revealed that the light yield of undoped ZnWO4 crystals varied with the purities of raw materials WO3 and ZnO. Raising the concentration of iron ions in ZnWO4 crystals resulted in reduction of the light yield from the lighter appearance. On the contrary, the light yield was enhanced by doping Ag2O, Nb2O5 and CeO2, equivalent to that observed in ZnWO4 crystals after oxygen-rich annealing at high temperature. The mechanisms of coloration and decolorization in doped ZnWO4 crystals were analyzed. And the relationship between enhanced scintillation properties and the color center complex of iron impurity and oxygen vacancy in the crystals was discussed.