Optical, luminescent and optical temperature sensing properties of (K0.5Na0.5)NbO3-ErBiO3 transparent ceramics

The lead-free 0.985(K0.5Na0.5)NbO3-0.015ErBiO3 (KNN-EB-0.015) ceramic was fabricated by pressureless sintering. It possessed a pure perovskite phase with pseudo-cubic symmetry. Due to the fine-grains, small-sized pores, dense microstructure and relaxor-like characteristics, the ceramic was optically clear, exhibiting the highest transmittances of ∼40% and ∼71% in the visible and infrared regions, respectively. The photoluminescence (PL) properties of the ceramic were studied, including the up-conversion (UC) green and red emissions, down-conversion near infrared emission as well as the emission lifetimes. The color-tunable (from green to yellow) UC emissions were observed by increasing the temperature, based on the temperature-dependent emission spectra, which also exhibited good thermal stability (52.6% of the initial intensity at 453 K) of the ceramic. Additionally, the temperature sensing properties were investigated using the fluorescence intensity ratio technique. A maximum sensitivity of ∼0.0048 K at 603 K was obtained. Combined with the good optical and electrical properties, the KNN-EB-0.015 transparent ceramic could be a promising candidate for multifunctional optoelectronic applications.