GdAlO_3:Er^(3+),Yb^(3+)荧光粉的制备与上转换发光性能

Preparation and Up-Conversion Photoluminescence Properties of GdAlO_3:Er^(3+),Yb^(3+) Phosphors

采用共沉淀、溶胶-凝胶和固相反应法制备了GdAlO3:Er3+,Yb3+荧光粉.借助X射线衍射、扫描电子显微镜、傅里叶变换红外光谱、N2-吸附、吸收光谱和荧光光谱等手段研究了不同方法制备的GdAlO3:Er3+,Yb3+荧光粉结构、形貌、表面基团和光吸收及上转换发光性能.结果表明:用共沉淀法比固相反应法和溶胶-凝胶法可以在更温和的条件下制得纯相GdAlO3:Er3+,Yb3+荧光粉,用共沉淀法和溶胶-凝胶法制备的GdAlO3:Er3+,Yb3+荧光粉颗粒都在纳米尺寸,溶胶-凝胶法制得的样品存在相对严重的颗粒团聚现象,而用固相反应法制备的荧光粉为微米级颗粒.GdAlO3:Er3+,Yb3+荧光粉在980 nm激发的上转换发射光谱包含波长为524和546 nm的绿光与659 nm的红光,且三种方法制备的样品绿光发射强度都显著高于红光.不同方法制备的荧光粉上转换发光强度和红光/绿光强度比相差较大,共沉淀法制备的样品上转换发光强度要显著高于固相法以及溶胶-凝胶法制备的样品,而溶胶-凝胶法制备的样品发光中红光/绿光相对强度比最高.红外光谱显示,不同方法制备的GdAlO3:Er3+,Yb3+荧光粉表面OH-、CO32-及CO2官能团含量不同,溶胶-凝胶法制备的样品要明显高些.基于红外光谱、不同Er3+和Yb3+离子掺杂浓度及不同激光功率上转换发光的结果,对Er3+和Yb3+之间的能量传递过程及不同方法制备荧光粉的上转换发光性能进行了讨论.

GdAlO3：Er3＋Yb3＋ phosphor was prepared by coprecipitation, sol-gel, and solid-state reaction methods, respectively. The effects of the preparation method on the structures, morphologies, surface species, light absorption, and up-conversion photoluminescence （UCPL） of the phosphors were investigated using powder X-ray diffraction （XRD）, scanning electron microscopy （SEM）, Fourier-transform infrared （FTIR） spectroscopy, N2 physisorption, absorption spectroscopy, and UCPL spectroscopy. The results showed that preparation using coprecipitation method gave a pure-phase GdAlO3：Er3＋Yb3＋ phosphor under milder conditions than those needed for the sol-gel or solid-state reactions. The particles of the phosphors prepared by coprecipitation and sol-gel methods were nanometer sized, and severe particle agglomeration occurred for the sol-gel sample. In contrast, the phosphor particles obtained using the solid-state reaction method were micrometer sized. Under excitation with 980 nm IR radiation, bright green UCPL at wavelengths of 524 and 546 nm, and red UCPL at 659 nm, were observed, with the green emission being dominant, irrespective of the preparation method. A comparison of the UCPL spectra of the phosphors prepared by different methods showed that the phosphor prepared by coprecipitation method showed a much higher emission intensity than the others, and the phosphor prepared by the sol-gel method gave the largest ratio of red to green emission intensities. The FTIR results showed that the phosphor prepared by the sol-gel method had larger amounts of surface CO2, CO3^2-, and OH- species. Based on the FTIR spectra, the UCPL results for phosphors with different concentrations of Er3＋ and Yb3＋ as well as the power dependences of UCPL intensities, the energy transfer processes between Yb3＋ and Er3＋ ions, and UCPL of theGdAlO3：Er3＋Yb3＋ phosphors prepared by different methods were discussed.