Synergistic use of Raman and photoluminescence signals for optical thermometry with large temperature sensitivity

Highlights: • We present an alternative approach for luminescence based optical thermometry by using a combination of Raman and PL signals from rare-earth doped crystalline phosphors. • We have introduced Raman-PL intensity ratio (RPIR) as an alternative thermometric parameter to estimate temperature sensitivity in such a mode of optical thermometery. • We achieved (i) large temperature tuning of color (red↔blue/green) and (ii) large values of sensitivities in a wide temperature range: +6.4 %K-1 at 65 K, +2.4 %K-1 at 303 K using this strategy on a Eu doped BaTiO₃. In this work we demonstrate that large temperature sensitivity over a wider temperature range is possible by adopting the dual use of Raman and photoluminescence (PL) signals emitted by rare-earth doped crystalline phosphors when excited by a suitable laser light. We define Raman-PL-intensity ratio (RPIR) as an alternative thermometric parameter to define temperature sensitivity and exploited the contrasting effect of temperature on the intensities of the PL and Raman lines of a Eu³⁺-doped BaTiO₃ ferroelectric phosphor and achieved large temperature tuning of color (red ↔ blue/green) and large relative temperature sensitivities in a wide temperature range: +6.4 %K⁻¹ at 65 K, +2.4 %K⁻¹ at 303 K. Our strategy offers greater flexibility for the design of phosphor systems for optical thermometry with high sensitivity.