xLiNbO3-(1-x)(K,Na)NbO3 ceramics: A new class of phosphors with tunable upconversion luminescence by external electric field and excellent optical temperature sensing property

In this study, Er3+-doped and Er3+/Yb3+-co-doped xLiNbO3-(1-x)(K,Na)NbO3 (xLN-(1-x)KNN) ferroelectric ceramics were synthesized by a solid state reaction process and the samples were found to exhibit tunable upconversion luminescence (UCL) under an external electric field as well as excellent optical temperature-sensing properties. By altering the polarization time, UCL intensity was effectively controlled under an external electric field. Furthermore, an optimal UCL was observed in a 0.4LN-0.6KNN:Er3+,3Yb3+ sample and its excellent optical temperature sensitivity (0.006 K−1 at 643 K) from 83 to 663 K was 131% higher than that of 0.4LN-0.6KNN:Er3+. These results suggested that xLN-(1-x)KNN ferroelectric ceramics were promising candidates for an opto-electronic integrator and optical temperature sensors with high sensitivity and broad temperature range.