Concentration- and temperature- dependent luminescence quenching and optical transition of Sr2GdTaO6: Eu3+ phosphor for potential applications in white LEDs
Li Wang, Yuhang Zhang, Yuhang Zhang, Duan Gao, Xuezhu Sha, Xin Chen, Yanqiu Zhang, Yanqiu Zhang, Jinsu Zhang, Xizhen Zhang, Yongze Cao, Yichao Wang, Xiangping Li, Sai Xu, Hongquan Yu, Baojiu Chen
Abstract
A series of Eu3+ doped Sr2GdTaO6 (SGT) phosphors with double perovskite structure were synthesized via a high-temperature solid-state reaction approach. The crystal structure, morphology and luminescence properties were characterized by means of X-ray diffraction, transmission electron microscope, luminescence spectroscopy and fluorescence decay lifetimes, respectively. Under the excitation of 394 nm, intense red emission in the visible region was observed in Eu3+ doped SGT phosphors, and the critical quenching concentration of Eu3+ in SGT phosphors was derived to be 15 mol%. The chromaticity coordinates and color purity of SGT: 15 mol% Eu3+ were calculated to be (0.61, 0.36) an 93.82%, respectively. Meanwhile, it was also confirmed that the electric quadrupole-quadrupole interaction is responsible for the luminescence concentration quenching of Eu3+. The internal quantum efficiency of SGT: Eu3+ phosphors with different Eu3+ concentrations were calculated. Furthermore, the crossover process was confirmed to be the main mechanism for luminescence thermal quenching based on the temperature-dependent emission spectra and temperature-dependent fluorescence lifetimes. In addition, the Judd-Ofelt parameters, radiative transition rates and branch ratios from the 5D0 emitting states to various lower energy states were evaluated with the aid of the Judd-Ofelt theory, respectively. All results indicate that SGT: Eu3+ samples are a promising red-emitting phosphor.