Photoluminescence and optical temperature sensing properties of Gd ₃Al ₃Ga ₂O ₁₂:Pr ³⁺ garnet transparent ceramics

Optical temperature sensors have garnered significant attention because of their ability to provide accurate, noncontact temperature measurements. Rare-earth element-doped Gd₃Al₃Ga₂O₁₂ (GAGG) ceramics are known for their excellent optical properties, stable crystal structure, good thermal stability, and tunable fluorescence characteristics. In this study, we innovatively introduced a series of Pr³⁺-doped GAGG garnet ceramics with high sensitivity for optical temperature sensing. The phase structure, morphology, and optical properties of the ceramics were investigated, and the optimal doping concentration was determined. The photoluminescence (PL) and optical temperature sensing properties of the GAGG:Pr³⁺ ceramics were thoroughly examined. The PL spectra of the GAGG:Pr³⁺ garnet transparent ceramics displayed multiple narrow emission peaks, and CIE plots indicated that the luminescence color was tunable within the green region. The emission intensities exhibited a quenching phenomenon at high rare-earth element doping concentrations and elevated temperatures. The optical temperature sensing properties of GAGG:Pr³⁺ were analyzed via the fluorescence intensity ratio (FIR) method, which is based on Pr³⁺ thermally coupled (³P₁ → ³H₅ and ³P₀ → ³H₄) and nonthermally coupled (³P₁ → ³H₅ and ¹D₂ → ³H₄) energy level pairs. The maximum relative sensitivities for the thermally coupled and nonthermally coupled energy level pairs of GAGG:Pr³⁺ reached 0.81% K⁻¹ (at 300 K) and 0.37% K⁻¹ (at 350 K), respectively, under 450 nm blue light excitation. These results suggest that GAGG:Pr³⁺ ceramics have significant potential for noncontact optical temperature sensing applications.