Temperature dependence of up-conversion luminescence and sensing properties of LaNbO: Nd/Yb/Ho phosphor under 808 nm excitation.

LaNbO: Nd/Yb/Ho phosphor was prepared by a conventional high temperature solid-state reaction method. The temperature dependence of up-conversion (UC) luminescence property of LaNbO: Nd/Yb/Ho phosphor under 808 nm excitation and the potential application of exploiting the red-to-green UC emission intensity ratio (I/I) of Ho in temperature sensing were studied. Two-photon processes were confirmed to be responsible for both the green and the red UC emissions at different temperatures by analyzing the excitation power density dependent UC luminescence spectra measured at different temperatures. The energy level diagram was drawn to analyze the UC luminescence mechanism of Ho. In addition, it was found that the ratio I/I of Ho was independent of the excitation power density of 808 nm laser under the current experimental condition, but it was sensitive to the temperature. And the temperature dependent UC luminescence spectra displayed that the ratio I/I exhibited a good linear increasing tendency with temperature rising. The obtained temperature sensing sensitivity was 2.04 × 10 K in the temperature range of 303-693 K. The results suggest that LaNbO: Nd/Yb/Ho phosphor may be a good candidate for application in optical temperature sensors.