(La_(0.88)Yb_(0.10)Ho_(0.02))_(2)W_(2)O_(9)荧光粉的上转换发光及双模式荧光测温

Up-conversion photoluminescence of(La_(0.88)Yb_(0.10)Ho_(0.02))_(2)W_(2)O_(9)phosphor and dual-mode thermometry

采用共沉淀法制备了Yb-Ho共掺的La_(2)W_(2)O_(9)纳米晶。采用X射线衍射(XRD),场发射扫描电子显微镜(FE-SEM)和荧光光谱(PL/PLE)对前驱体及产物进行表征。系统地研究了样品包括功率/温度依赖发射光谱、潜在上转换发光机制、主发射的衰减动力学、发光颜色等上转换发光特性及荧光测温性能。结果表明在不同功率980 nm光源激发下,(La_(0.88)Yb_(0.1)Ho_(0.02))_(2)W_(2)O_(9)荧光粉在654 nm出现最强发射峰,对应于Ho^(3+)离子的_(5)F_(5)→_(5)I_(8)跃迁。在298-548 K温度范围内的上转换发光性能研究表明所得荧光粉可通过荧光强度比模式(FIR)和荧光寿命模式(FL)实现双模式荧光测温。在980 nm光源激发下,所得荧光粉可基于Ho^(3+)的最强发射峰^(5)F_(5)→^(5)I_(8)(654 nm)与(^(5)F_(4),^(5)S_(2))→^(5)I_(8)(544 nm)和(^(5)F_(4),^(5)S_(2))→^(5)I_(7)(759 nm)两发射峰的荧光强度比(FIR)进行荧光测温。I_(654)/I_(759)荧光强度比模式测温最大绝对灵敏度(S_(A))及相对灵敏度(S_(R))分别为266×10^(-4)和3266×10^(-4)K^(-1),I_(654)/I_(544)荧光强度比模式测温的最大绝对灵敏度(S_(A))为81×10^(-4),最大相对灵敏度(S_(R))为3427×10^(-4)K^(-1)。随着温度的升高,所得荧光粉的发光颜色发生人眼可见的明显变化,从室温的绿色变为高温的橙红色。此外,本工作荧光粉可基于主发射峰的荧光寿命进行测温,在298-548 K范围内主发射峰荧光寿命与温度呈指数减小关系,通过FL模式测温S_(A)、S_(R)最大值分别为997×10^(-4)K^(-1)、1184×10^(-4)K^(-1)。

In this work,Yb-Ho co-doped La_(2)W_(2)O_(9)nanocrystals were prepared by co-precipitation followed calcination method.The precursors and the calcination products were characterized by X-ray diffraction(XRD),field emission scanning electron microscopy(FE-SEM)and fluorescence spectroscopy(PL/PLE).The upconversion luminescence including power/temperature dependent emission,decay kinetics of the main emission,emission color,underlying UC mechanism,and luminescence thermometric performance were systematically investigated.The results show that(La_(0.88)Yb_(0.1)Ho_(0.02))_(2)W_(2)O_(9)phosphor has the strongest emission at 654 nm under 980 nm laser excitation,corresponding to the^(5)F_(5)→^(5)I_(8)transition of Ho^(3+)ions.The up-conversion luminescence of the phosphor was studied in the temperature range of 298-548 K.It is found that the obtained phosphor can be used as dual-mode thermometry via fluorescence intensity ratio mode(FIR)and fluorescence lifetime mode(FL).The fluorescence intensity ratios of the strongest emission of^(5)F_(5)→^(5)I_(8)(654 nm)to that of(^(5)F_(4),^(5)S_(2))→^(5)I_(8)(544 nm)and(^(5)F_(4),^(5)S_(2))→^(5)I_(7)(759 nm)transition respectively were used for temperature measurement.The maximum absolute sensitivity(S_(A))and relative sensitivity(S_(R))of I_(654)/I_(759)were 266×10^(-4)and 3266×1010^(-4)/K.The maximum absolute sensitivity(S_(A))of I_(654)/I_(544)was 81×10^(-4)/K,and the maximum relative sensitivity(S_(R))was 3427×10^(-4)/K.With the increase of temperature,the luminescence color of the phosphor changed obviously from green at room temperature to orange-red at high temperature.In addition,the fluorescence lifetime of the main emission of the obtained phosphor was applied for thermometry.In the range of 298-548 K,the fluorescence lifetime of the main emission shows an exponential decrease trend with the increasing temperature.The maximum values of S_(A)and S_(R)measured by FL mode are 997×10^(-4)/K and 1184×10^(-4)/K,respectively.