Luminescence of Triple Perovskite Ba₃MgTa₂O₉:Dy³⁺ Up to 1100 °C

The luminescence response of Dy3+-doped Ba3MgTa2O9 (BMTO:Dy) between room temperature and 1100 °C was studied in the context of high-temperature thermosensitive phosphors. Single-phase BMTO:Dy was synthesized via solid-state reaction. Powder X-ray diffraction, diffuse reflectance spectroscopy, and density-functional theory calculations were used to probe its crystal and electronic structure. Variable-temperature time-resolved decays of the 4I15/2 → 6H15/2 transition of Dy3+ (457 nm) were collected and the temperature dependence of the excited-state average lifetime was quantitatively analyzed with two objectives: establish mechanisms driving luminescence thermal quenching and assess the potential of BMTO:Dy as a high-temperature luminescent thermometer. Quenching was observed above 450 °C and appeared to be driven by thermal ionization of the 4I15/2 excited state to the host’s conduction band, with a temperature-dependent activation barrier in the 1.1–1.5 eV range. The occurrence of high-order (≈21) multiphonon relaxation to lower-lying 4f levels as an additional or alternative quenching pathway at high temperatures could not be ruled out. As a luminescent thermometer, the operational temperature range of BMTO:Dy was between 450 and 1100 °C and temperature sensitivities ranged between ≈2.1 % °C–1 at 538 °C and ≈0.9 % °C–1 at 1100 °C. Findings presented herein expand the library of high-temperature thermosensitive phosphors to group V d0 refractory metalates, a class of materials that offers the opportunity to tailor luminescence response through rational tuning of crystal, vibrational, and electronic structure.