燃烧法制备MgGa_2O_4∶Co^(2+)纳米晶及其发光性能研究

Synthesis of MgGa_2O_4∶Co^(2+) Nanocrystals by Combustion Method and its Optical Properties

采用低温燃烧法在500℃成功制备了MgGa2O4及MgGa2O4∶Co2+纳米晶。以推进剂化学为理论依据,对原料的配比进行了理论计算,并通过考察不同点火温度、原料配比对产品质量的影响,找出了合成MgGa2O4的优化条件。X-射线衍射、扫描电镜、透射电镜、荧光光谱等方法对产品表征的结果显示,尖晶石型MgGa2O4晶体是反应生成的唯一晶体,燃烧产生的气体使产品包含大量的气孔;合成的晶体结晶度高,排列规整;掺杂的Co2+取代了MgGa2O4晶体中四面体位上的Mg2+;发射光谱中可见光区和近红外光区两个发射峰分别归因于四面体格位中Co2+的4T1(4P)→4A2(4F)能级跃迁和4T1(4P)→4T2(4F)能级跃迁。

Superfine MgGa2O4 and Co2 ＋ -doped MgGa2O4 nanocrystals were prepared at 500℃ by low- temperature combustion method without any further calcination process. The ratios of reactants were calculated theoretically based on thermo-chemical calculations of propellant chemistry theory, and the optimal procedure parameters were selected by adjusting ratios of reactants and ignition temperatures. The results of powder X-ray diffraction indicated that the as-prepared MgGa2 O4 nanocrystals were the only crystalline phase. The photo of SEM showed that the products contained pores because the gases were given out instantly during combustion reaction. The photo of TEM showed that the products exhibited high crystallinity and regular arrangement. The observed excitation and emission spectra of the nanocrystalline powders in the visible and near infrared regions were characteristic of tetrahedral Co2 ＋ ions,which indicated that Co2 ＋ ions entered into MgGa2 O4 crystal by replacing tetrahedral Mg2 ＋ ions. The visible and near infrared luminescent bands were assigned to the spin-allowed 4 T1 （4 P） →4 A2 （4 F） and 4 T1 （4P） → 4T2（4F） transitions.