Yb-Mn dimer tailored upconversion luminescence in CaWO4:Er3+/Yb3+/Mn2+green phosphors for thermometry and optical heating

Upconversion emission in CaWO4:Er3+/Yb3+/Mn2+ phosphor synthesized via ethylene glycol route has been analyzed on excitation under 980 nm diode laser. The structural information and morphology have been widely studied through different experimental techniques. The Yb-Mn dimer is inserted to explicate the energy transfer mechanism which brings about twofold enhancement in the green emission. The optical thermometric perfor-mance of the developed phosphor based on the thermally coupled green levels of Er3+ (2H11/2 and 4S3/2) ions in the range of 303-623 K has been explored using the fluorescence intensity ratio (FIR) technique. The maximum sensitivity of 1.04 % K-1 at 303 K is obtained for the optimized phosphor with a thermal resolution of 0.4 K. Additionally, the internal heating characteristics of the said phosphor developed by the variation in excitation laser power is also studied which is found to raise from 265 to 563 K. Under 980 nm excitation the prepared phosphors exhibit strong green emission with a color purity of 98 %. The energy transfer mechanism, population redistribution ability and thermal stability have been discussed in detail and the possible field of applications have been explored.

Automated summary

Upconversion emission of CaWO4:Er3+/Yb3+/Mn2+ phosphor synthesized via ethylene glycol route under 980 nm diode laser excitation is analyzed. Structural information, morphology, and the energy transfer mechanism with Yb-Mn dimer are studied. Optical thermometric performance based on the thermally coupled green levels of Er3+ ions and the internal heating characteristics are explored. The prepared phosphors exhibit strong green emission and high color purity under 980 nm excitation.