CeO2:Eu3+粉末的溶胶-凝胶法制备及发光性能研究

采用溶胶-凝胶法制备了不同浓度Eu3 掺杂的CeO2发光粉,样品粉末在紫外光激发下发出明亮的橙红色光.利用X射线衍射(XRD)、热重-差热分析(TG-DTA)和光致发光光谱(PL)对样品的结晶过程和发光性质进行了表征.XRD分析表明在0.2at.%～10at.%的Eu3 掺杂范围内,用溶胶-凝胶法合成的样品在500℃就结晶成纯相的CeO2:Eu3 多晶粉末.由于Ce4 和Eu3 离子半径十分接近,因而Eu3 在CeO2中具有较高的固溶度.PL激发谱中出现在300～390 nm的宽带激发峰起源于基质CeO2的吸收,电子吸收能量后,发生O2--Ce4 的电荷迁移,再将能量传递给Eu3 .PL发射谱显示Eu3 含量为6at.%的样品发光强度最强,随后出现浓度猝灭.导致发光出现浓度猝灭的机制是电偶极-电四极相互作用.样品烧结温度的升高,促使晶粒长大和结晶完整性提高,从而显著提高了CeO2:Eu3 粉末的发光强度.

Preparation of CeO2: Eu3+ Powders by Sol-Gel Method and Their Photoluminescence Properties

CeO2 Eu3+ phosphor powders with various Eu3+ concentrations have been prepared by the sol-gel method. Upon excitation with UV light, the CeO2 : Eu3+ powders showed bright orange red emissions due to the 4f-4f transitions of Eu3+ ions. X-ray diffraction (XRD), TG-DTA and Photoluminescence (PL) measurements were used to characterize the samples. XRD analysis showed that the powders with pure cubic fluorite-type CeO2 phase at an up to 10at. % concentration of Eu3+ was obtained at the sintering temperatures from 500 to 1 250 degrees C. The large solubility for doping Eu3+ ions in CeO2 is due to the nearness of ionic radius between Ce4+ and Eu3+. It was also found that an increase in sintering temperature promotes the grain growth of CeO2 and improves its crystallinity. The excitation spectra of the CeO2 : Eu3+ powders were dominated by a broad band at 300-390 nm, suggesting the efficient energy transfer from the O(2-) - Ce4+ charge-transfer state to the doping Eu3+ in the CeO2 : Eu3+ powders. The CeO2 : Eu3+ phosphor powders with a 6at. % concentration o f Eu3+ sintered at 1 250 degrees C revealed the strongest photoluminescence and then in abruptly decreased with increasing the doping concentration indicating the concentration quenching. The mechanism of concentration quenching could be explained as the result of the dipole-quadrupole interaction of neighboring Eu3+.