A highly thermal-stable red-emitting tantalate phosphor for WLED and multiple-mode optical temperature sensor dual-applications

Abstract

Recently, more and more attention has been concentrated on luminescence materials activated with rare-earth ions for white light-emitting diodes (WLEDs) or optical thermometers. However, due to their opposite requirements for thermal response, it is hard to realize the above dual applications in the same material. Herein, a red-emitting tantalate phosphor, Gd3TaO7:Eu3+, was designed and prepared to solve the problem. The emission of Eu3+ in the phosphor was surprisingly observed to be different from that in most of the reported red phosphors activated with Eu3+, that is, the emissions coming from the f - f transitions of Eu3+ exhibit severe splitting, and the intensities of several strong transitions are not very different. According to the structural and spectral analyses, the reasons may be the highly covalent and polarized lattice environments of Eu3+ in this material. When excited with 393 nm, the temperature-dependent photoluminescence (TDPL) of Gd3TaO7:Eu3+ presents a normal thermal quenching and the integrated intensity at 500 K keeps 90.8 % compared to that at 300 K. Whereas the TDPL presents an edge abnormal thermal quenching phenomenon upon the excitation of 330 nm. Taking advantage of the special TDPL characteristics, a WLED device and a multiple-mode optical thermometer are successfully realized in this material. The former has excellent performances with high Ra of 88.8 and low CCT of 3882 K, and the latter includes one type of excitation intensity ratio and two types of fluorescence intensity ratio with the maximal relative temperature sensitivities of 0.92 % K−1, 0.97 % K−1 and 0.92 % K−1, respectively. The results reveal that Gd3TaO7:Eu3+ phosphor has a great prospect in WLED and multiple-mode optical temperature sensor dual-applications, and this work may provide a new and effective strategy for developing multifunctional optical materials.