The usability of the Judd-Ofelt theory for luminescent thermometry using Eu³⁺-doped phosphate glass

The Judd-Ofelt theory, which is the most thorough and insightful method to determine theoretically the luminescent properties of the trivalent rare earth dopants, is here tested on Eu³⁺-doped glasses in the P₂O₅ – SrO – CaO – Na₂O system to assess their usefulness as luminescent thermometers. It is demonstrated that the thermometric sensitivity (change of the emission lines ratio in response to change in temperature) can be estimated using the Judd-Ofelt theory and aligns well with the experimentally obtained values. It is shown here that the addition of B₂O₃ or SiO₂ in a phosphate network increases the absolute sensitivity due to an increase in the phosphate network connectivity while having no significant impact on the site of Eu³⁺ ions. The applicability of the Judd-Ofelt theory for predicting the thermometric parameters of a glass luminescent material, without the time-consuming measurement of the glasses spectroscopic properties as a function of temperature, is clearly demonstrated and allows for further development of novel efficient luminescent thermal sensors with high sensitivity.