A colorimetric optical thermometry of host-sensitized Pr³⁺-doped niobate phosphors based on electronic-rich-site...

Most praseodymium-doped red-emitting phosphors need high-temperature synthesis conditions with a reducing atmosphere. The niobate matrix selected in this work provides a sufficient electron-rich-site environment for praseodymium through charge migration, and praseodymium can be self-reduced in air atmosphere, which is safe and environmentally friendly. By building the [NbO₆] group → Pr³⁺ energy transfer and finely modifying the doping concentration of Pr³⁺ ions, we constructed a dual-luminescence-system of the [NbO₆] group and Pr³⁺. Thereby, optical temperature measurement based on fluorescence intensity ratio (FIR) technology of Pr³⁺ ions and [NbO₆] groups was carried out using non-thermal coupling pairs, through the Boltzmann fitting and integral calculation, the maximum S_r and S_a values were 2.25% K^-1 and 0.0049 K^-1 at 403 K and 443 K, respectively, the S_r value is four times that obtained from the thermal coupling of Pr³⁺ ions, which exceeded most values previously reported for the fluorescence powder. Accordingly, we also studied the thermal sensitivity of Er³⁺ ions and Eu³⁺ ions mono-doped CaNb₂O₆ substrates. Results reveal that CaNb₂O₆:Pr³⁺/Er³⁺/Eu³⁺ phosphors have splendid temperature sensitivity and have far-reaching application prospects in the field of temperature measurements.