Boltzmann thermometry: Eu3+-doped monoclinic Y2O3 and Y2O3@SiO2 nanoparticles

Abstract

During last decade optical thermometry has gained considerable attention due to the possibility to determine temperature remotely in cases when traditional contact methods fail. The most widespread type of optical temperature sensors is based on monitoring luminescence intensity ratio between transition originated from thermally coupled energy levels. Eu3+ ions own the largest energy gap between thermally coupled 5D1 and 5D0 energy levels among all lanthanides, which guarantees a high thermal sensitivity of Boltzmann-type thermometry. Here, uncoated m-Y2O3:Eu3+ and core-shell m-Y2O3:Eu3+@SiO2 nanophosphors have been successfully utilized as ratiometric thermal sensors within the 298–873 K range. It was shown that the calculation method (integral or peak intensities) only slightly affects thermal sensitivity. SiO2 coating significantly enhances emission intensity and increases lifetime, but has no noticeable effect on thermal sensitivity. m-Y2O3:Eu3+ nanophosphor has the best thermometric characteristics of Sr = 0.96 % K-1 at 373K and δT = 0.5 K.