Tailoring luminescence thermometry for environmental barrier coatings via Yb3+/Y3+ ratio and Eu3+ concentration engineering in yttrium rare earth silicate phosphors

To address the need for non-contact temperature monitoring of environmental barrier coatings (EBCs) used in aircraft engines, phosphors of (Eu x Y 1-x ) 2 SiO 5 and (Eu 0.2 Yb x Y 0.8-x ) 2 SiO 5 with varying Yb 3+ /Y 3+ composition ratios were prepared via high-temperature solid-state synthesis. The study investigates how Eu 3+ concentration and the Yb 3+ /Y 3+ ratio influence phase structure, luminescent behavior, and temperature-sensitive properties. The results indicate that both sample series are homogeneous monoclinic solid solutions. Substitution of Eu 3+ for Y 3+ causes lattice expansion, and the 612 nm orange-red emission increases with concentration without exhibiting significant concentration quenching within the studied range (up to 20 mol%). However, increasing the Yb 3+ /Y 3+ composition ratio promotes energy transfer from Eu 3+ to Yb 3+ , causing a sharp decrease in luminescence. Based on these findings, (Eu x Y 1-x ) 2 SiO 5 is established as a suitable material for temperature-sensitive studies. Temperature measurements combined fluorescence intensity and lifetime as dual parameters. The 2 mol% Eu 3+ sample shows an optimal linear response of emission intensity over 25-600 °C, while the 20 mol% Eu 3+ sample overcomes interference from blackbody radiation with the strongest high-temperature signal (signal-to-background ratio ≥ 0.10), extending the upper limit of reliable temperature measurement by lifetime to the highest achievable temperature of 850 °C. Together, these two methods cover a temperature range from room temperature to 850 °C. Twelve high-low temperature cycles confirm the material’s structural stability and good measurement reproducibility. This study provides experimental evidence for composition design and temperature-measurement parameters of fluorescent temperature-sensing materials for EBCs, and the system is expected to be an ideal candidate for non-contact temperature measurement in EBCs.