CaMoO4∶Tb^3＋发光材料的制备和发光性质的研究

Preparation and Luminescent Properties of CaMoO_4:Tb^(3+)

用共沉淀法制备了样品CaMoO_4:Tb^(3+)的前驱物,经TG-DTA测试表明:样品在850℃时有能量吸收峰,即达到样品反应的活化点。XRD谱图分析显示,焙烧后样品CaMoO_4:Tb^(3+)为CaMoO_4的白钨矿结构,但峰位发生了右移,说明晶体内部产生了微小的晶体缺陷,推测该缺陷可能是由晶胞内2个Tb^(3+)取代了3个Ca^(2+)形成空穴而引发的。通过对激发谱图的测试发现,此种缺陷结构有利于使MoO_4^(2-)发射特征峰(488 nm)的能量有效地传递给Tb^(3+),使Tb^(3+)的4f电子发生跃迁,特别使Tb^(3+)的~7F_6→~5D_4(488 nm)电子跃迁大大加强,因而在样品CaMoO_4:Tb^(3+)的发射谱图(λ_(ex)=488 nm)中,自激活荧光体MoO_4^(2-)的发射强度被大大减弱,而Tb^(3+)的~5D_4→~7F_5(544 nm)跃迁的绿光发光强度被大大增强,使该材料成为有潜在应用价值的发光材料。

The precursor of the sample CaMoO4 ： Tb^3＋ was prepared by the coprecipitation method. TG-DTA spectra show that there is, at 850 ℃, an energy absorption peak, suggesting that the sample reaches the activation spot of its response. The XRD pattern of the roasted sample shows that CaMoO4 ： Tb^3＋, in the single phase, is a representative scheelite structure of CaMoO4, but the peaks shift toward right, implying that tiny crystal defect in the crystal is produced. The defect is likely to be formed by the formation of the holes as two Tb^3＋ replace three Ca^2＋ in a cell. The excitation and emission spectra of the sample were investigated and revealed that the defect structure of the sample is in favor of the energy transfer of the characteristic peak （488 nm） of the MoO4^2- effectively to Tb^3＋ , and makes the 4f electrons of the Tb^3＋ transit, especially the ^7F6→^5 D4 electronic transition （488 nm） of the Tb^3＋ , to be greatly strengthened. As a result, the emission spectra with λex =488 nm show that the emission intensity of the spontaneously activated fluorescence MoO4^2- is greatly weakened, while the green light luminescence in tensity of the ^5D4→^7F5 transition （544 nm） of the Tb^3＋ is greatly enhanced. This suggests that the sample CaMoO4 ： Tb^3＋ will become the luminescence material with potentially great application value.