Upconversion luminescence and temperature sensing properties of Yb2(MoO4)3:Ln3+ (Ln = Ho, Tm, Er) phosphors based on energy transfer

Abstract

Yb₂(MoO₄)₃:Ln³⁺ (Ln = Ho, Tm, Er) phosphors were synthesized by a hydrothermal method with further calcination. The crystal structure and morphology of the samples were characterized by X-ray diffraction and scanning electron microscopy. The effects of rare earth ion interaction in the Yb₂(MoO₄)₃:Ln³⁺ phosphors on the upconversion (UC) luminescence properties and energy transfer process at different doping concentrations were discussed. It is concluded that by doping Ho³⁺, Tm³⁺, and Er³⁺ in the Yb₂(MoO₄)₃ host, the phosphors emit orange-yellow, blue and green light, respectively, and the energy transfer from Yb³⁺ → Ho³⁺/Er³⁺ and Yb³⁺ → Tm³⁺ is a two and three photon process, respectively. Under the excitation of a 980 nm laser, by changing the Ho³⁺/Tm³⁺ ratio in doped Yb₂(MoO₄)₃, we have realized the transition of phosphors from cold white light to warm white light. The temperature sensitivity of the ²H_11/2 and ⁴S_3/2 energy levels of Yb₂(MoO₄)₃:Er³⁺ in the range of 323–573 K was studied by the FIR technology. The experimental results show that the maximum absolute sensitivity was 0.0081 K⁻¹ at 573 K and the maximum relative sensitivity was 0.01 K⁻¹ at 323 K. Compared with other materials, the Er³⁺ doped Yb₂(MoO₄)₃ phosphor is an excellent optical temperature sensing material.