Effect of Ca doping on the structure and scintillation properties of ZnWO 4

The future application of ZnWO 4 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 ZnWO 4 . X‐ray diffraction analysis revealed that there is no mixing in the CaWO 4 –ZnWO 4 pseudobinary system due to a significant mismatch of the crystal structures of CaWO 4 and ZnWO 4 . The lattice parameters of Ca‐doped ZnWO 4 samples obtained from X‐ray powder diffraction data confirmed this finding. It is also shown that ZnWO 4 retains the monoclinic wolframite structure when cooling, at 12 K exhibiting the following lattice parameters: a = 4.6826(2) Å, b = 5.7088(2) Å, c = 4.9230(2) Å and β = 90.541(2)°. The scintillation light yield of the Zn 1− x Ca x WO 4 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 ZnWO 4 is expected to facilitate production of a single‐crystalline scintillator. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)