Bridgman growth and temperature dependent photoluminescence properties of ZnMoO4 crystals by modification with Zn2+, Mo6+, Ca2+ and W6+ ions

Abstract Zinc molybdate (ZnMoO4) crystal is considered as a promising scintillator for neutrinoless double beta decay. In this paper, ZnMoO4 crystals by modification with, such as Zn2+ ions or Mo6+ ions in excess of 0.2 mol% and doped by 0.5 mol% Ca2+ ions or W6+ ions, were grown by the vertical Bridgman method using spontaneous crystallization. All the as-grown slightly adjusted ZnMoO4 crystals appeared light orange and the transmittance of crystals with the thickness of 2 mm were about 85% from 600 to 800 nm, which is higher than that with stoichiometry (75%). ZnMoO4 crystals were indirect crystals with optical energy band gap of 3.69 eV and luminesced from 77 K to room temperature, while the intensities were very weak at room temperature. With the temperature increasing, the luminescence light yield of ZnMoO4 crystals decreased. ZnMoO4 crystal doped by 0.5 mol% W6+ ions had the highest light yield at 77 K ZnMoO4 crystal doped by 0.5 mol% Ca2+ ions had the shortest decay time (τ = 9.1 μs at 300 K and τ = 72.7 μs at 77 K).