n(Zn)：n(Ga)比值对合成ZnGa2O4结构及光致发光性能的影响

以ZnO和HGaO₂为原料,用不同配比合成出系列ZnGa₂O₄,并对其晶体结构和发光性能进行了研究。用荧光分光光度计检测了ZnGa₂O₄的激发和发射光谱,用X射线衍射仪检测了ZnGa₂O₄的衍射图谱,用热重差热仪绘制了TGA-DAT曲线。对检测结果分析认为:1.ZnGa₂O₄属于尖晶石结构,稍过量的Zn或Ga能进入ZnGa₂O₄结构中,并对ZnGa₂O₄的晶格常数产生一定影响。2.ZnGa₂O₄存在两个自激发光中心,当Ga稍过量时,自激发光中心是四面体镓氧键T_d(Ga-O)],最大激发波长约248nm,最大发射波长约367nm;当Zn稍过量时,自激发光中心是八面体镓氧键O_h(Ga-O)],最大激发波长约270nm,最大发射波长约441nm。当n(Zn):n(Ga)在理论值附近,激发和发射光强度最大,而且光谱峰位发生了红移。3.ZnGa₂O₄的热稳定性能非常好。上述结论对研究ZnGa₂O₄基质或掺杂的发光材料具有一定意义。

Influence of the Ratio of n(Zn)∶n(Ga) on the Structure and the Photoluminescence Properties of ZnGa2O4

Recently, zinc gallate (ZnGa₂O₄) phosphors have gained much attentions for use in vacuum fluorescent displays (VFD), thin film electroluminescent devices (TFED), field emission displays (FED) and low-voltage cathodeluminescence (LVC), because they exhibit higher chemical stability than sulfide phosphors. ZnGa₂O₄ is also expected as a new photoluminescence material. The influence of the ratio of n(Zn):n(Ga) on the structure and the photoluminescence properties of ZnGa₂O₄ was investigated mainly. Using our rich compounds of gallium, ZnGa₂O₄ with the nominal formula with ZnO/HGaO₂ (n(Zn):n(Ga)) ratio ranging from 0.350 to 0.650 was prepared by high temperature solid-state reaction methods. ZnO-HGaO₂ system compounds near the ZnGa₂O₄ stoichiometric composition have been tested with diverse characterization techniques. Fluorescence spectrophotometer was used to measure the photoluminescence excitation and emission spectra of ZnGa₂O₄. X-ray diffraction measurements were performed to investigate the phase states in the ZnGa₂O₄ phosphors dependent on the mixture molar ratio of ZnO and HGaO₂. Thermal analyzer was used for recording TGA-DTA curves of ZnGa₂O₄. The results show that ZnGa₂O₄ has a spinel structure, consists of a cubic cell with Fd3m symmetry, which contains a close-packed array of 32 oxygen atoms with cations in tetrahedral and octahedral interstices. The excess Ga or Zn is soluble in ZnGa₂O₄ and don't affect the spinel lattice of ZnGa₂O₄. The lattice constants increased along with increasing of n(Zn):n(Ga) ratio. When Zn excess, the formula of ZnGa₂O₄ changed into Zn(Ga_1-xZn_x)₂O₄,this formula leaded to the increase O^2- vacancy. When Ga excess, the formula of ZnGa₂O₄ changed into (Zn_1-xGa_x)Ga₂O₄,this formula leaded to the increase Zn²⁺ vacancy. ZnGa₂O₄ is a new n-semiconductor material, its lattice interval exist the vacancies and ions, belong to structure defect or crystal defect. The luminescence mechanism is similar the luminescence of semiconducter, with an optical band gap of 4.4 eV. ZnGa₂O₄ is a kind of self-activated luminescence material with two self-activated optical center, e.g. T_d(Ga-O)] and O_h(Ga-O)], its excitation and emission spectras are wider. In n(Zn):n(Ga)≤0.500, the absorption band at 248 nm and the fluorescence band at 367 nm originated from self-activation optical centers of the tetrahedral T_d(Ga-O)] in the spinel lattice. In n(Zn):n(Ga)≥0.550, the absorption and the fluorescence band at 270 nm and 441 nm originated from self-activation optical centers of the octahedral O_h(Ga-O)] in the spinel lattice. The peak of excitation and emission shifted to longer wavelength when n(Zn):n(Ga) ratio between 0.500 and 0.550. TGA-DTAanalyses showed ZnGa₂O₄ had excellent chemical stability properties. These results can help improve understanding ZnGa₂O₄ or doped ZnGa₂O₄ phosphors for the application research with high brightness.