Luminescent thermometry using borogermanate glass doped with europium recovered from electronic waste

Borogermanate glasses doped with Eu 3+ ions are promising materials for luminescent thermometry due to their high thermal stability and optical properties. Recovering rare-earth elements from electronic waste (e-waste) offers a sustainable source for such functional materials. Here we synthesized a borogermanate glass incorporating 30 wt% e-waste-derived Eu 3+ ions via melt-quenching and characterized its photoluminescence behavior for temperature sensing. The glass exhibited characteristic Eu 3+ emission transitions with temperature-dependent luminescence intensity ratio (LIR) between thermally coupled 7 F 0 and 7 F 2 energy levels, following Boltzmann distribution in the 300-400 K range. The energy gap was determined as 926 ± 44 cm -1 , with a maximum relative thermal sensitivity of 1.48 % K -1 at 300 K and a temperature uncertainty of 1.7 K. The obtained primary luminescence thermometer proved to be stable under cyclic temperature changes. At 400 K, a mean LIR value of 0.16545 was obtained, with a standard deviation of 0.00277 (RSD = 1.67%). These findings demonstrate that borogermanate glasses derived from e-waste can serve as sustainable and reliable primary luminescent thermometers for advanced optical sensing applications.