Thermally driven chromatric evolution and charge transfer in Pr3+/Eu3+-doped fluorophosphate glasses

This research focuses on developing durable oxyfluoride glass matrices doped with praseodymium and europium ions for advanced luminescence thermometry applications. Rare earth ions provide sharp emission lines ideal for temperature sensing, but thermal treatment on phosphate glasses induces a recurring, understudied chromatic change. During the annealing process, a charge transfer occurs between non bridging oxygen atoms and rare earth ions possessing high reduction potentials. This chemical process successfully reduces the ions to a divalent state, simultaneously triggering structural defects known as Phosphorus Oxygen Hole Centers. These resulting color defects manifest as a broad absorption band centered between 500 and 600 nanometers, causing a highly significant visual color variation in the glass structure. Ultimately, this innovative work explicitly aims to synthesize these specific luminescent materials and completely characterize the precise structural relationship between different annealing temperatures, ion reduction, and color center formation to optimize these robust optical temperature sensors effectively.