Monoclinic Er3+ -doped Y2O3 Phosphor: Advancing Ratiometric Optical Temperature Sensing Beyond the Cubic Phase

Abstract

Luminescence thermometry has been established as a reliable technique for remote temperature sensing in cases where traditional contact methods are unsuitable. Er3+ -doped oxide materials are frequently utilized for optical thermal sensing due to the fact that the erbium ion possesses a complex energy level structure, which includes both thermally and nonthermally coupled levels suitable for providing ratiometic strategy. The diversity of oxide structures offers opportunities for crystal phase engineering to optimize properties. Monoclinic Y2O3:Er3+ nanoparticles were demonstrated, for the first time, as ratiometric thermal sensors across a wide temperature range of 98-873 K. The thermometric performance of the monoclinic nanoparticles is comprehensively compared with that of the conventional cubic Y2O3:Er3+ sample. The best relative thermal sensitivity of ~1.2 % K -1 @298K was found to be comparable for both crystal phases, while the monoclinic polymorph exhibited a superior temperature resolution, reaching a maximum of 0.24 K. These results highlight the potential of monoclinic Y2O3:Er3+ as a superior alternative to cubic phase counterparts for high precision luminescence thermometry applications.