Optical temperature sensing properties of novel RE3+ (RE = Er, Ho) doped BaLa2Ti3O10 phosphors

A novel luminescent material of BaLa₂Ti₃O₁₀:RE³⁺ was synthesized by the high-temperature solid phase method, with a typical layered structure belonging to a special crystal system. Under the excitation of 980 nm, BaLa₂Ti₃O₁₀:4 %Er³⁺ exhibits characteristic emissions centered at 531 nm, 551 nm and 668 nm. It is noteworthy that the color of BaLa₂Ti₃O₁₀:3 %Ho³⁺ shows a strong green emission at 551 nm and a weak red emission near 664 nm, also represents adjustable yellow-green light with the change of 980 nm laser pumped powers. The optical temperature sensing properties were checked by employing different strategies, relating to the thermally-coupled-levels (TCLs) and nonthermally-coupled-levels (NTCLs). The results show that the maximum relative sensitivity of TCLs based on BaLa₂Ti₃O₁₀:Er³⁺ is 0.68 % K⁻¹ (305 K). Similarly, the maximum sensitivity of TCLs is 0.89 % K⁻¹ (313 K) in BaLa₂Ti₃O₁₀:Ho³⁺, which performs well from 313 K to 513 K. It has been found the samples using FIRs of TCLs can produce higher absolute (S_a) and relative (S_r) sensitivities compared with those using Fluorescence Intensity Ratios (FIRs) of NTCLs. The multiple FIRs also achieved superior levels of temperature resolution and repeatability in all cases. Generally, this work provides favorable candidates for the temperature sensors.