Luminescence Properties Of ZnGa₂O₄ Phosphors

ZnGa₂O₄ is a kind of self-activated luminescence material which attracts more and more attention recently. It has higher chemical stability in severe atmosphere such as ultra-high electrical field or electron bombardment than traditional sulfide materials, So it has more applications in various fields such as TFED,FED,VFD.The main work is using high temperature solid state reaction , ZnO and Ga₂O₃ with high purity as raw materials, preparing different ZnGa₂O₄ samples under different molar ratios of raw materials(ZnO: Ga₂O₃=0.8: 1, 0.9: 1, 1: 1, 1: 0.9, 1 : 0.8), different temperatures(from 1000 ℃ to 1400 ℃ ), different reaction atmospheres (sintering in air and C reduced atmospheres ) ,and measuring the luminescence spectra thoroughly. Luminescence characters of the samples are in good correspondence with the former works: the PL is a broad emission with the peak at about 430nm in the blue region, The origin of the peak is the transition from Ga³⁺ to the O^2- around in the normal octahedral. PL emission also appears around 690nm, and there is luminescence possibility around 505nm, which have little reports before. The origins of the 690nm and 505nm emission are considered as V_O*→ O^2- transition after the singly charged ion oxygen vacancy appeared in the octahedral structure, and ²E_A→ ⁴A₂ transition of Ga³⁺ in a relatively distorted octahedral after some Zn²⁺ are substituted by Ga³⁺.After excited by 254nm UV lamps, two new long-lasting luminescence peaks 505nm and 690nm were detected for the first time ,which shows green and red luminescence respectively, this is a result which never have been researched. We measured long lasting luminescence spectra, and the time based peak intensity decay curves; the origin of the luminescence are discussed, and the effects of synthesis parameters such as molar ratio of the raw materials, the temperatures and C reduced atmospheres are concluded , Our conclusion is that the 505nm peak comes from the ²E_A→ ⁴A₂ transition of Ga³⁺ in a relatively distorted octahedral after some Zn²⁺ are substituted by Ga³⁺; and the 690nm peak comes from the V_O*→ O^2- transition after the singly charged ion oxygen vacancy appeared in the octahedral structure.