The use of a material as CPSD relies on the efficiency of the process of phonon transport through the crystal. Therefore, knowledge of lattice dynamics of the crystal is of great importance. So far there is lack of information on the above properties not only for the prospective materials, but even for well-known scintillation materials when low-temperature applications are considered. In order to resolve this problem this study turned our attention to modelling techniques and the precise determination of structural parameters at different temperatures.
 

The thermal behaviour of structure was studied using the high-resolution powder diffraction technique and synchrotron radiation. The experiments were carried out at the beamline B2 on high resolution powder diffractometer equipped with a closed-cycle helium cryostat. All measurements were performed in DebyeScherer geometry (0.3 mm capillaries) using the Image Plate detector OBI and X-ray wavelength of 0.4996 Å. The measurements were carried out in the temperature range 12 – 300 K. First, the sample was cooled from room temperature to 12 K and a set of diffraction patterns (37 for CaMoO4 and 16 for CaWO4) in the 2θ region 2 – 40o was collected during cooling. The temperature was then stabilised at 12 K and another set of powder diffraction patterns was collected in the temperature range 20 - 300 K with temperature increments of 20 K. The measured XRD data where analysed using the full profile Rietveld method implemented in the WinCSD program package. Additionally, neutron scattering experiments were performed at the D2b instrument (ILL) for calcium tungstate.

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