Growth of scintillation crystal ZnWO4 by bridgman method

ZnWO4 polycrystalline material were prepared by solid-state sintering process or wet-chemical method. A transparent ZnWO4 single crystal with size of 25 mm×60 mm were grown by vertical Bridgman method. ZnWO4 polycrystalline material and as-grown single crystal were characterized with crystalline phase by X-ray powder diffraction. The spectral properties of the crystal wafers were investigated by means of optical transmittance, photoluminescence and X-ray stimulated luminescence spectra. The annealing effect of the single crystal in oxygen atmosphere was also discussed by comparing the optical spectra of the crystal wafers before and after annealing treatment. The results show a typical optical transmittance in 400-800 nm wavelength range with an absorption edge of 380 nm or so. The single crystal exhibits a fluorescence emission with central wavelength at 470 nm under violet photonic stimulation or X-ray excitation. The crystal colouration could alleviate and optical transmittance could improve significantly after the single crystal was annealled in oxygen atmosphere at 980.