Effect of Ca doping on the structure and scintillation properties of ZnWO4

The future application of ZnWO4 scintillator in a cryogenic search for rare events is the motivation for optimization of this material. We present results on the effect of Ca doping on the structure and scintillation properties of ZnWO4. X-ray diffraction analysis revealed that there is no mixing in the CaWO4 - ZnWO4 pseudobinary system due to a significant mismatch of the crystal structures of CaWO4 and ZnWO4. The lattice parameters of Ca-doped ZnWO4 samples obtained from X-ray powder diffraction data confirmed this finding. It is also shown that ZnWO4 retains the monoclinic wolframite structure when cooling, at 12 K exhibiting the following lattice parameters: a = 4.682,6(2) angstrom, b = 5.7088(2) angstrom, c = 4.9230(2) angstrom and beta = 90.541(2)degrees. The scintillation light yield of the Zn1-xCaxWO4 was measured using the multi-photon counting technique and it is found that small concentrations of Ca (x = 0.001 - 0.02) cause no deterioration of this parameter. Ca doping of ZnWO4 is expected to facilitate production of a single-crystalline scintillator. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.