Thermal expansion, luminescence, and scintillation properties of CaMoO₄ crystals grown by the vertical Bridgman method

CaMoO₄ crystal is a promising scintillator for investigating the neutrinoless double beta decay process and is commonly grown by the Czochralski method. In this study, CaMoO₄ single crystals were grown by the vertical Bridgman method using both spontaneous crystallization and seed crystal approaches. The CaMoO₄ crystal grown using the spontaneous crystallization approach exhibited yellow, light blue, and deep blue colours (from top to middle part of the ingot). The thermal expansion coefficients, α^a and α^c, were calculated to be 6.11 × 10⁻⁵/°C, and 23.58 × 10⁻⁵/°C, respectively. The optical transmission spectra and photo- and thermally stimulated luminescence spectra of the crystals before and after thermal annealing were also investigated. The yellow cubic CaMoO₄ crystal showed the highest x-ray-stimulated luminescence intensity and the best light output under the excitation of a ¹³⁷Cs radioactive source.