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

Yb3+/Er3+-doped Bi-2(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, Bi-2(MoO4)(3):Yb3+/Er3+ phosphors exhibited strong upconversion green light and weak red light emissions. By doping WO42- in Bi-2(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 Bi-2(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+ (H-2(11/2)/S-4(3/2) -> I-4(15/2)) in Bi-2(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 Bi-2(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.