Synthesis and Er³⁺ spectroscopic properties study of Er₂O₃ .3Nb₂O₅ phosphor for temperature sensing

Er₂O₃ .3Nb₂O₅ phosphor phase was synthesized by sintering the mixture of Er₂O₃ and Nb₂O₅ powder with a molar ratio of 1:3 at 1200 °C for 76 h. The new polycrystalline phase formation is justified by comparing the X-ray diffraction pattern with those patterns of raw material Er₂O₃ and Nb₂O₅, and of the ErNbO₄ and Er₃NbO₇ phosphors. Optical absorption and emission characteristics of the Er₂O₃ .3Nb₂O₅ phosphor were investigated in comparison with the ErNbO₄ and Er₃NbO₇. Due to structural differences, the spectroscopic properties of the three phosphors show some differences. The Er₂O₃ .3Nb₂O₅ phosphor shows stronger upconversion (UC) emission than the other two, and the energy-transfer UC and/or excited state absorption plays a dominant role in the UC emission. Further study of temperature effect on the UC emission shows that both the peaking and integrated UC intensities decrease almost linearly with the raised temperature, and the ⁴S_3/2 → ⁴I_15/2 (560 nm) UC intensity shows a stronger temperature dependence, implying that the Er₂O₃ .3Nb₂O₅ phosphor is promising for temperature sensing. The feasibility of using the UC emissions to realize the temperature sensing is discussed on the basis of color-modulation principle. In addition, the lifetimes of typical Er³⁺ emissions at 555, 672, 1006 and 1530 nm of Er₂O₃ .3Nb₂O₅ were measured.