Synthesis and luminescence properties of Yb3+/Er3+-doped Bi2(MoO4)3−z(WO4)z phosphors for optical thermometry†

Yb³⁺/Er³⁺-doped Bi₂(MoO₄)_3−z(WO₄)_z phosphors were synthesized via a hydrothermal method combined with subsequent calcination. Under the excitation of a light source of 980 nm, Bi₂(MoO₄)₃:Yb³⁺/Er³⁺ phosphors exhibited strong upconversion green light and weak red light emissions. By doping WO₄²⁻ in Bi₂(MoO₄)₃:Yb³⁺/Er³⁺ phosphors, the upconversion luminescence intensity of the phosphors significantly enhanced, which is 42 times higher than that of the undoped WO₄²⁻ phosphor. With an increase in WO₄²⁻ doping content, the final color coordinates of Bi₂(MoO₄)_3−z(WO₄)_z:Yb³⁺/Er³⁺ phosphors were (0.2352, 0.7274), which is closer to the standard green CIE coordinates. The maximum CP of WO₄²⁻-doped phosphors is as high as 116.68%, which is 74.44% higher than that of the undoped WO₄²⁻ phosphor. Based on the thermally coupled energy levels (TCLs) of Er³⁺ (²H_11/2/⁴S_3/2 → ⁴I_15/2) in Bi₂(MoO₄)_2.7(WO₄)_0.3:14%Yb³⁺,3%Er³⁺ phosphor, the S_R value reached a maximum of 0.0081 K⁻¹ at 323 K and the S_A value reached a maximum of 0.0099 K⁻¹ at 398 K. The obtained Bi₂(MoO₄)_3−z(WO₄)_z:Yb³⁺/Er³⁺ phosphors are suitable for upconversion luminescent materials for green displays and have potential advantages in optical temperature measurement.