Regulation of optical, thermal, and electrical properties of GaNbO4 crystal by Mg²⁺ doping

In this paper, GaNbO4 crystal properties were regulated by Mg2+ doping. The refractive indexes, optical properties, and thermal properties were characterized, the influence of Mg2+ doping and air annealing on the conductivity and photoluminescence properties of GaNbO4 was systematically studied. The Mg2+ doping causes the ultraviolet absorption edge of GaNbO4 crystal blue shift, and the band gap of Mg: GaNbO4 crystal is 3.463 eV. The thermal expansion coefficient in b-direction was presented, which is -0.977 x 10(-6) K-1; the hightemperature resistivity of the Mg: GaNbO4 crystal decreases from 1.7 x 10(9) to 3.0 x 10(6) W center dot cm in the temperature range of 500 to 800 degrees C, decreasing by about an order of magnitude after air annealing. The photoluminescence spectrum shows an enhanced blue emission in Mg: GaNbO4 crystals, and x-ray photoelectron spectroscopy was measured, the element's chemical states and oxygen vacancies in the crystal were analyzed. The regulation mechanism of the crystal properties was discussed in detail.