Multifunctional optical thermometry using dual-mode green emission of CaZrO₃:Er/Yb/Mo perovskite phosphors

The weak emission intensity of rare-earth element-doped dual-mode materials leads to low-sensor sensitivity, which is a challenge in optical sensor applications. The present work achieved high-sensor sensitivity and high green color purity based on the intense green dual-mode emission of Er/Yb/Mo-doped CaZrO₃ perovskite phosphors. Their structure, morphology, luminescent properties, and optical temperature sensing properties have been investigated in detail. Phosphor shows a uniform cubic morphology with an average size of approximately 1 μm. Rietveld refinement confirms the formation of single-phase orthorhombic CaZrO₃. Under the excitation of 975 and 379 nm, the phosphor emits pure green up and down-conversion (UC and DC) emission at 525/546 nm corresponding to ²H_11/2/⁴S_3/2-⁴I_15/2 transitions of Er³⁺ ions, respectively. Intense green UC emissions were achieved because of energy transfer (ET) from the high-energy excited state of Yb³⁺-MoO₄^2- dimer to the ⁴F_7/2 level of Er³⁺ ion. Furthermore, the decay kinetics of all obtained phosphors confirmed ET efficiency from Yb³⁺-MoO₄^2- dimer to Er³⁺ ions, leading to strong green DC emission. Moreover, the DC of the obtained phosphor shows that a sensor sensitivity value of 0.697% K^-1 at 303 K is higher than the UC (0.667% K^-1 at 313 K) because the thermal effect generated by the DC excitation source light is ignored compared with UC luminescence. CaZrO₃:Er-Yb-Mo phosphor shows intense green dual-mode emission with high green color purity, 96.50% of DC and 98% of UC emissions, and high sensitivity, making it suitable for optoelectronic devices and thermal sensor applications.