White up-conversion luminescence and highly-sensitive optical temperature sensing in Na3La(VO4)2:Yb,Er,Tm,Ho phosphors

In this work, tunable white up-conversion luminescence was achieved in the Yb3+, Er3+, Tm3+, Ho3+ co-doped Na3La(VO4)2 phosphors under 980 nm excitation. The emissions of three primary colors are mainly attributed to the 2H11/2/4S3/2 → 4I15/2 transitions of Er3+, 1G4→3H6 transition of Tm3+, and 5F5→5I8 transition of Ho3+. White luminescence characteristics and mechanisms of up-conversion system were investigated in detail. In addition, the temperature sensing behaviors of multiple levels emission combinations for Na3La(VO4)2:Yb3+,Er3+,Tm3+,Ho3+ were analyzed by employing thermally coupled and non-thermally coupled energy levels. Based on the emissions of 3F2,3/1G4 energy levels, the maximum relative and absolute sensitivities were obtained to be 2.20%/K and 0.279 K–1. The design of up-conversion luminescence materials with high-quality white luminescence and excellent sensitivity performance is critical in the field of optical applications.