Novel optical temperature sensors based on the emission of the Pr3+ ions doped Ca3(M,Ga)5O12 (M5+ = Nb, Ta) garnet phosphors

Pr3+-doped Ca3(Nb,Ga)5O12 (Pr:CNGG) and Ca3(Ta,Ga)5O12 (Pr:CTGG) phosphors with garnet structure have been systematically investigated as optical thermometric materials for potential applications in the field of sensing technology, for the first time to our knowledge. The ceramic samples of Pr:CNGG and Pr:CTGG with different concentrations of Pr3+ ions have been obtained by the solid-state reaction method. A comparative analysis to evidence the influence of the position of the inter-valence charge transfer (IVCT) states on the excited-state dynamics of Pr3+ ions in CNGG and CTGG materials is presented. The optical thermometric properties of the Pr:CNGG and Pr:CTGG samples were studied. The luminescence thermal quenching mechanisms of the 3P0 and 1D2 levels were investigated in detail based on the luminescence intensity ratio (LIR) of 1D2→3H4 / 3P0→3H4 (I606/I487) transitions over an extended temperature range (10–700 K). The maximum relative sensitivities were determined to be 1.64% K−1 at 10 K for 7 at% Pr:CTGG and 2.4% K−1 at 430 K for 1 at% Pr:CNGG, thus proving their potential as high-sensitivity temperature sensors in cryogenic and high-temperature domains, respectively.