Investigation of up-conversion luminescence properties and optical temperature sensing behavior in CaMoO4: Pr3+/ Yb3+ phosphors

Abstract

CaMoO₄:Pr³⁺/Yb³⁺ phosphors were synthesized employing the solid-state reaction, whereas the temperature dependence of up-conversion (UC) luminescence properties under 980 nm excitation and the potential application as an optical temperature sensor were investigated. X-ray diffraction (XRD) analysis demonstrated the absence of secondary phase, confirming the formation of a single phase for the materials investigated and that co-doped samples have the same structure as CaMoO₄. Phosphors were excited at 980 nm demonstrating blue, green, red emissions correlated to transitions from Pr³⁺ ions. Moreover, optical temperature-sensing properties were analyzed employing the Fluorescence Intensity Ratio (FIR) technique, whereas relative (S_R) and absolute (S_A) sensitivities were calculated from Thermally Coupled Levels (TCL) and Non-Thermally Coupled Levels (NTCL) from Pr³⁺ ions. The highest sensitivity values were obtained for NTCL 600 nm/650 nm, with S_A = 14.81 × 10⁻³ K⁻¹ and S_R = 1.93 % K⁻¹ demonstrating that the CaMoO₄:Pr³⁺/Yb³⁺ system could be employed as optical temperature sensors in the high-temperature region.