A novel optical temperature sensor and energy transfer properties based on Tb 3+ /Sm 3+ codoped SrY 2 (MoO 4 ) 4 phosphors.

A series of SrY 2 (MoO 4 ) 4 phosphors doped and co-doped with Tb 3+ /Sm 3+ ions was synthesized to develop new optical temperature sensor materials. The structures, morphologies, and luminescent characteristics of these phosphors were thoroughly investigated. Luminescence spectra of mono-doped SrY 2 (MoO 4 ) 4 phosphors were measured under the excitation at 375 and 403 nm corresponding to direct excitation of Tb 3+ and Sm 3+ , respectively. The characteristic luminescence bands corresponding to electronic transitions of terbium and samarium ions were detected and investigated for different dopant concentrations. The emission spectrum of the Tb 3+ /Sm 3+ co-doped sample exhibited a total of five distinct emission peaks, indicating an energy transfer from Tb 3+ to Sm 3+ ions. The energy transfer efficiency from Tb 3+ ions to Sm 3+ ions was investigated in detail. At elevated temperatures, Tb 3+ and Sm 3+ exhibited distinct thermal sensitivities in their emission and excitation spectra, leading to evident thermochromic behavior. The fluorescence intensity ratio (FIR) was utilized with dual center to evaluate the temperature sensitivity of SrY 2 (MoO 4 ) 4 :Tb 3+ /Sm 3+ phosphors. The temperature sensing mechanism relied on the emission band intensity ratios of the 4 G 5/2 → 6 H 5/2 , 4 G 5/2 → 6 H 9/2 , and 4 G 5/2 → 6 H 7/2 transitions of Sm 3+ in conjunction with the 5 D 5/2 → 7 F 5/2 transitions of Tb 3+ . This approach demonstrated high thermal sensitivity values, reaching up to 0.9% K -1 . The studied nanoparticles exhibited sub-degree thermal resolution, making them suitable candidates for precise temperature-sensing applications.