Effect of annealing conditions on the luminescence properties and thermometric performance of Sr 3 Al 2 O 5 Cl 2 :Eu 2+ and SrAl 2 O 4 :Eu 2+ phosphors.

We report on the synthesis, photoluminescence optimization and thermometric properties of Sr 3 Al 2 O 5 Cl 2 :Eu 2+ and SrAl 2 O 4 :Eu 2+ phosphor powders. The photoluminescence of Sr 2.9 Al 2 O 5 Cl 2 :0.1Eu 2+ phosphors exhibits a blue-shift with an increasing annealing temperature owing to a decrease in the crystal field strength of the host caused by evaporation of Cl from the material. The quenching of the blue band in favour of the red band observed in the luminescence spectra of Sr 2.9 Al 2 O 5 Cl 2 :0.1Eu 2+ with an increased annealing temperature was explained using the mechanism of the Landau-Zener transitions. The quantum yield and the lifetime of the phosphors depend on the annealing temperature. Phosphor samples annealed at 850 °C, 1000 °C, 1200 °C and 1500 °C were found to be potential luminescence thermometers using the luminescence spectral method. For Sr 3 Al 2 O 5 Cl 2 :Eu 2+ annealed at 1000 °C, the temperature-dependent dual-band intensity ratio demonstrated a high-temperature sensitivity of ∼1.47%/°C in the temperature range of 23 °C to 40 °C which is superior to other reported phosphors with a microsecond decay time, suggesting that the material has potential for sensitive thermometry applications at ambient temperatures.