Preparation and upconversion luminescence properties of GdTaO<sub>4</sub>:RE/Yb(RE=Tm, Er) phosphor through experimental optimization design

Abstract

In order to obtain the maximum characteristic intensities of the up-conversion luminescence in GdTaO<sub>4</sub>:RE/Yb(RE = Tm, Er) series, we establish the regression equation between the luminescent intensity of the phosphors and the rare earth doping concentration upon the 980 nm laser excitation based on the experimental optimization design. The Tm<sup>3+</sup>/Yb<sup>3+</sup> doping samples are combined with the uniform design and quadratic general rotation combination design, meanwhile the Er<sup>3+</sup>/Yb<sup>3+</sup> doping samples are optimized by the uniform design and cubic orthogonal phosphor step by step. The relationship between concentration and luminous intensity is analyzed. The results show that the changes of concentration of RE<sup>3+</sup> (RE = Tm, Er) and Yb<sup>3+</sup> can exert a significant effect on luminous intensity, and there exist extreme points of luminescent intensity in the test space. By solving the regression equation, we obtain the optimal doping concentration. The optimal samples are also prepared by the high-temperature solid state method. The XRD diffraction patterns of the optimal samples are analyzed. The results show that the samples are of pure phase, the doping of Li<sup>+</sup> flux will inhibit the generation of reaction impurity phase, and the doping of rare earth will shift the diffraction peak to a high angle, with the peak shape remaining unchanged. The relationship between excitation power and luminescent intensity is analyzed. The results show that the blue light emission of Tm<sup>3+</sup>/Yb<sup>3+</sup> co-doped phosphor is a three-photon process, and the green light emission of Er<sup>3+</sup>/Yb<sup>3+</sup> co-coped phosphor is a two-photon process. The relationship between sample temperature and luminescent intensity is analyzed. The luminescent intensity of the sample decreases with the increase of the temperature, indicating temperature quenching. Finally, the quenching activated energy of the sample is calculated.