Power-dependent up-conversion emissions and temperature sensing properties of NaYF4:Er/Yb@NaYF4 phosphors

Abstract

Rare earth doped luminescent materials have unique up-conversion properties and can be applied to optical temperature sensing. In this work, the power-dependent emission intensity from bare core NaYF4:Er/Yb and core–shell structured NaYF4:Er/Yb@NaYF4 phosphors and the temperature sensing properties of NaYF4:Er/Yb@NaYF4 phosphors are investigated. The NaYF4:Er/Yb and NaYF4:Er/Yb@NaYF4 phosphors are prepared through typical co-precipitation method. The enhancement factor of emissions located at 520, 540 and 654 nm reach 1.51, 1.42 and 1.75, respectively, which is originated to the suppression of surface quenching. The enhancement factor decreases slowly with excitation power increasing due to the more sensitivity to laser power of the bare core phosphors. In addition, the green emissions (520 and 540 nm) exhibit distinct temperature-dependent behaviors, including relatively sensing sensitivity and thermal repeatability stability. The maximal relatively sensing sensitivity reaches 1.2% K−1 at 294 K and The value of thermal repeatability stability reaches 98.4%.