Synthesis of LixNayK(1-x-y) YF4: Yb3+, Er3+ by hydrothermal method and its upconversion properties

Upconversion materials have significant application prospects in many fields due to the advantages of being excited by infrared light. However, the development of upconversion materials is constrained by low upconversion efficiency and low luminescence intensity. The aim of this work is to improve the luminescence efficiency and intensity of fluorine-based upconversion luminescent materials through ternary alkali metal doping. A series of ternary alkali metal-doped Li x Na y K (1−x−y) YF 4 :Yb 3+ , Er 3+ novel upconversion luminescent materials were synthesized by a one-step facile hydrothermal method, and their mechanisms were explored. The results show that the doping of Li, Na, and K ions changes the crystal structure of Li x Na y K (1−x−y) YF 4 :Yb 3+ , Er 3+ , thereby affecting the spatial structural relationship between the rare-earth ions, which changes the energy transfer efficiency to them. The luminescence intensity of the prepared Li x Na y K (1−x−y) YF 4 :Yb 3+ , Er 3+ was 30 times higher than that of the undoped samples when doped with Li, Na, and K ions in a molar ratio of 10:6:9. This study provides a simple and effective method for the preparation of upconversion materials with excellent luminescent properties.