Search for new molybdenum‐based crystal scintillators for the neutrino‐less double beta decay search experiment

Studies of Li${}_2$O–MoO${}_3$, Cs${}_2$MoO${}_4$–MoO${}_3$, and Na${}_2$O–MoO${}_3$ phases have helped us to develop several new crystals such as Li${}_2$MoO${}_4$, Li${}_4$Mo${}_5$O${}_{17}$, Li${}_2$Mo${}_4$O${}_{13}$ Cs${}_2$MoO${}_4$, Cs${}_2$Mo${}_2$O${}_7$, Cs${}_2$Mo${}_3$O${}_{10}$ Na${}_2$Mo${}_2$O${}_7$, and Na${}_6$Mo${}_{11}$O${}_{36}$ grown by a Czochralski method. Syntheses of the polycrystalline materials are discussed based on the thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) analysis and the crystals' structures are reported based on the X‐ray powder diffraction (XRD) analysis. Luminescence properties of the crystals from room temperature to 10 K are studied by exciting the crystal with a 280 nm light emitting diode (LED). The scintillation light yields of the crystals at different low temperatures are studied by exciting the crystal with strontium‐90 (${}^{90}$Sr) beta source. The developed crystals are not luminescent at room temperature. At cryogenic temperature, however, they become luminescent with longer decay times. This work also reports on the luminescence and scintillation properties of ZnMoO${}_4$, PbMoO${}_4$, Pb${}_2$MoO${}_5$, and CaMoO${}_4$ crystals which have been grown at other institutes. The newly developed crystals' results are compared with the result of a standard CaMoO${}_4$ crystal. Among the new Mo‐based crystals, the Na${}_2$Mo${}_2$O${}_7$ crystal shows the most promising properties for the neutrino‐less double beta decay (0νββ) search experiments at cryogenic temperature. (© 2019 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)