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 = 4.6826(2) Å, b = 5.7088(2) Å, c = 4.9230(2) Å and β = 90.541(2)°. The scintillation light yield of the Zn1−x Cax WO4 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. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)