铝酸钙基稀土荧光粉CaAl_(4)O_(7)∶Eu^(3+)的制备及热稳定性研究

Preparation and thermal stability of calcium aluminate rare earth phosphor CaAl_(4)O_(7)∶Eu^(3+)

在目前商用白光LED的实际应用中,存在发光色温高、显色指数低及热稳定性差等问题。为了改进白光LED存在的不足,使其更适用于人类生活的需求,本文通过共沉淀法合成了一系列CaAl_(4)O_(7)∶Eu^(3+)高温红光荧光粉,采用扫描电子显微镜、X射线衍射仪、能谱仪分别对样品的形态、结构、组成元素及分布进行表征,并通过荧光光谱仪对CaAl_(4)O_(7)∶Eu^(3+)的荧光特性及热稳定性进行了研究。实验结果表明,最佳样品为CaAl_(4)O_(7)∶0.02Eu^(3+)。其激发光谱中,在393及464 nm处有两个强光激发峰,分别属于^(7)F_(0)→^(5)L_(6)及^(7)F_(0)→^(5)D_(2)跃迁;在发射光谱中,最强发射峰位于612 nm,为^(5)D_(0)→^(7)F_(2)跃迁的窄带红光发射;最佳样品的发光具有负的热猝灭效应,其在90℃时发射光强度最大,此时积分荧光发射强度为30℃时初始值的114.5%。当测试温度升高至150℃时,积分荧光发射强度仍为初始值的108%;在CaAl_(4)O_(7)∶0.02Eu^(3+)的原型红光LED的电致发光测试中,发射红光比随着驱动电流的增大而增大。CaAl_(4)O_(7)∶0.02Eu^(3+)荧光粉具有优异的高温荧光特性,满足LED对荧光粉的发光热稳定性的要求,表明其在WLEDs领域具有潜在的应用前景。

In the current practical application of commercial white LEDs,there are problems such as high color temperature,low color rendering index,and poor thermal stability.In order to improve the shortcomings of white LEDs and make them more suitable for the needs of human life,a series of high-temperature red-emitting phosphors CaAl_(4)O_(7)∶Eu^(3+)were synthesized by co-precipitation method.The morphology,structure,and elemental composition and distribution of samples were characterized by Scanning Electron Microscope(SEM),X-ray Diffractometer(XRD),and Energy Dispersive Spectrometer(EDS),respectively.The fluorescence properties and fluorescence thermal stability of CaAl_(4)O_(7)∶Eu^(3+)were studied by fluorescence spectrometer.Results show that the best sample was CaAl_(4)O_(7)∶0.02 Eu^(3+).In the excitation spectrum,there were two strong excitation peaks at 393 and 464 nm,which belonged to ^(7)F_(0)→^(5)L_(6) and ^(7)F_(0)→^(5)D_(2) transitions respectively.In the emission spectrum,the strongest emission peak located at 612 nm,which was the narrow-band red emission of ^(5)D_(0)→^(7)F_(2) transition.The luminescence of the best sample had a negative thermal quenching effect,and its emission intensity reached the maximum at 90℃,at which the integrated fluorescence emission intensity was 114.5%of the initial value at 30℃.When the test temperature increased to 150℃,the integrated fluorescence emission intensity maintained at 108%of its initial value.In the electroluminescence test of the prototype red LED of CaAl_(4)O_(7)∶0.02 Eu^(3+),the emission ratio of red light increased with the increase in driving current.The CaAl_(4)O_(7)∶0.02 Eu^(3+)phosphor has excellent high-temperature fluorescence properties,which meets the requirements of LEDs for the fluorescence thermal stability of phosphors,indicating that it has potential application prospects in the field of WLEDs.