Optical properties of Er3+, Yb3+ co-doped calcium zirconate phosphor and temperature sensing efficiency: Effect of alkali ions (Li+, Na+ and K+)

Abstract

The Er3+/Yb3+ co-doped calcium zirconate phosphors have been synthesized through solid state reaction method. The structural characterizations confirm the crystalline nature of the phosphor. The Er3+, Yb3+ co-doped phosphor emits intense green emission centered at 523 and 544 nm due to the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions, respectively and weak red emission at 662 nm due to 4F9/2 → 4I15/2 transition of Er3+ on excitation with 976 nm radiation. The emission intensity of the green band dominates over the red band. When the alkali ions (Li+, Na+, K+) are added in the Er3+/Yb3+ co-doped phosphor, the emission intensities of bands enhance significantly. The fluorescence intensity ratio correspond to 523 and 544 nm peaks at different temperatures have been obtained which confirm the temperature sensing ability of the samples. In presence of alkali ions, the temperature sensor sensitivity increases and is maximum for K+ co-doped phosphor. It is found that the energy gap between 2H11/2 and 4S3/2 levels increases with crystallinity in order of K+>Na+>Li+> without alkali ion. Thus, the Li+, Na+ and K+ incorporated Er3+, Yb3+ co-doped calcium zirconate phosphor may be useful for photonic devices and temperature sensor.