Bridgman growth and luminescence properties of Na2Mo2O7 crystal

This research presents a Bridgman method for the crystal growth of disodium dimolybdate (Na2Mo2O7, NM2O) crystals and understanding their luminescence mechanism. An NM2O 2 O crystal with a size of 23 * 23 * 90 mm(3) was grown using the vertical Bridgman method. The cleavage of the NM2O crystal was analyzed by X-ray diffraction and scanning electron microscopy, which showed that the crystal cleaves along the (001) plane and the cleavage planes appear in a step pattern. Its luminescence properties were studied using transmission spectra and laser- stimulated luminescence spectra, which showed that the transmittance of a 5 mm thick sample reaches 85 % in the range of 500-700 nm with the absorption cutoff edge at 360 nm, resulting in the optical band gap of 3.35 eV. Under excitation of a 278 nm laser beam, the sample exhibited dual-peak emission, typically at around 598 nm and 673 nm, consistent with radioactive annihilation of the self-trapped exciton on [MoO6](6)- - and [MoO4](2)- groups respectively. Also the luminescence at low temperatures were measured and discussed. All results can benefit the crystal growth and application to the 0v beta beta experiments for the functional material.