White up-conversion La₂Mo₂O₉:Yb³⁺, Ho³⁺, Tm³⁺ phosphors based on dual luminescence centers for high-sensitive optical thermometry

In this paper, the La₂Mo₂O₉:Yb³⁺, Ho³⁺, Tm³⁺ phosphors are successfully synthesized through simple solid-state method. The white up-conversion luminescence is realized by appropriately varying the co-doped concentrations of Ho³⁺, Tm³⁺. The up-conversion luminescence characteristics and energy transfer processes of La₂Mo₂O₉:Yb³⁺, Ho³⁺, Tm³⁺ are specifically analyzed upon 980 nm laser excitation. A strategy to enhance the optical temperature sensing performance is demonstrated via flexibly selecting diverse non-thermally coupled energy levels of dual luminescence centers with the fluorescence intensity ratio technology. The maximum values of absolute and relative sensitivity for the thermometer reach 0.2478 K⁻¹ and 1.38% K⁻¹ based on the non-thermally coupled energy levels of ³F_2,3 (Tm³⁺)/⁵S₂,⁵F₄ (Ho³⁺). The luminescence color of La₂Mo₂O₉:Yb³⁺, Ho³⁺, Tm³⁺ phosphors can maintain in the white region over the whole measured temperature range. These results indicate that the phosphors possess great potential in broad application prospects in the aspects of anti-counterfeiting, displays and non-contact temperature sensing.