A six-mode optical thermometry rooted from the distinct thermal behavior of SrLaLiTeO6: Mn4+, Eu3+ double perovskites and their potential application in wavelength detection

Developing accurate and reliable temperature sensors with better temperature sensitivity, high spatial, temporal, and temperature resolutions via cost-effective methods is a major concern in the scientific world. Optical thermometry has gained worldwide interest owing to its unique features compared to its conventional counterparts. For the first time, a six-mode optical thermometry is implemented in Eu3+ and Mn4+ co-doped SrLaLiTeO6 (SLLT) double perovskites. X-ray diffraction analysis identified the crystal structure of the phosphor as monoclinic (P21/n). Additionally, the Raman and FTIR spectra confirmed the successful incorporation of Eu3+ and Mn4+ ions into the SLLT host. Thermometric properties of SLLT: Eu3+, Mn4+ over a wide temperature range were analyzed using fluorescence intensity ratio (FIR) of Mn4+ to Eu3+ emissions, TCL-based FIR, dual excitation single emission band (SBR) ratio, the ratio of charge transfer absorption edge of the host to 4f-4f absorption of Eu3+ ions, lifetime and line broadening methods. A maximum temperature sensitivity of 1.97% K−1 at 200 K is obtained using the intensity ratio of absorption bands in the excitation spectra, 0.33% K−1 at 340 K is obtained using the lifetime method, and 0.20% K−1 at 500 K is obtained using the line broadening method. The study envisages double perovskites as potential optical temperature sensors if a proper sensing method is identified to detect temperature. SLLT: Eu3+, Mn4+ is also examined for wavelength detection in the range 270–330 nm and proves to be a promising candidate for wavelength detection with maximum wavelength sensitivity of 8.09% nm−1 at 305 nm.