Luminescence temperature sensing based on spectral characteristic of CeF3-TbF3-YF3 nanoparticles

When $\mathrm{Ce}^{3+}$ ions are excited, intense peaks of luminescence of $\mathbf{T b}^{3+}$ ions are observed, which indicates an obvious energy transfer from $\mathrm{Ce}^{3+}$ to $\mathrm{Tb}^{3+}$. It has been shown that the ratio of the intensities of the luminescence bands $\mathrm{Ce}^{3+}$ to $\mathbf{T b}^{3+}$ is a decreasing function depending on temperature. The ratio of the intensities of the luminescence bands of $\mathrm{Ce}^{3+}$ and $\mathrm{Tb}^{3+}$ ions (in the range of $303-523 \mathrm{~K}$) was used as a temperature-dependent parameter. The rate of decrease in the LIR function decreases with increasing temperature for different concentrations of $\mathbf{T b}^{\mathbf{3 +}}$ ions. It has been suggested that this phenomenon is due to the presence of two processes populating the ${ }^{5} \mathrm{D}_{4}$ state of the $\mathbf{T b}^{3+}$ ion. There are a multiphonon non-radiation transition from the ${ }^{5} D_{3}$ to ${ }^{5} D_{4}$ level of the $\mathbf{T b}^{3+}$ ion (more temperature-dependent) and cross-relaxation between $\mathbf{T b}^{3+}$ ions, which was estimated as less temperature-dependent process.