Preparation and upconversion luminescence properties of GdTaO₄:RE/Yb(RE=Tm, Er) phosphor through experimental optimization design

Abstract

In order to obtain the maximum characteristic intensity of the up-conversion luminescence in GdTaO<sub>4</sub>:RE/Yb(RE=Tm, Er) series, we established 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 were combined with the uniform design and quadratic general rotation combination design, meanwhile the Er<sup>3+</sup>/Yb<sup>3+</sup> doping samples were optimized by the uniform design and cubic orthogonal phosphor step by step. The relationship between concentration and luminous intensity was analyzed. The results showed that the concentration changes of RE<sup>3+</sup> (RE=Tm, Er) and Yb<sup>3+</sup> had a significant effect on luminous intensity, and there were extreme points of luminescent intensity in the test space. By solving the regression equation, we gained the optimal doping concentrations. The optimal samples were also prepared by high-temperature solid state method. The XRD diffraction patterns of the optimal samples are analyzed. The results show that the samples are 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 without changing the peak shape. 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-doping phosphor is a three-photon process, and the green light emission of Er<sup>3+</sup>/Yb<sup>3+</sup> co-doping 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 increasing of the temperature, indicating temperature quenching. Finally, the quenching activated energy of the sample is calculated.