Photoluminescence, ferroelectric, dielectric and piezoelectric properties of Er-doped BNT-BT multifunctional ceramics

0.93(Bi0.5−x/0.93Erx/0.93Na0.5)TiO3-0.07BaTiO3 photoluminescent ceramics have been prepared by a conventional ceramic fabrication technique and their photoluminescence, ferroelectric, dielectric and piezoelectric properties have been studied. Under an excitation of 980 nm, the ceramics exhibit visible up-conversion luminescent emissions at 532 nm (green), 540 nm (green) and 600 nm (red), as well as broadband down-conversion luminescent emissions in near-infrared (1.44-1.66 μm) and mid-infrared (2.62-2.84 μm) regions. The quenching concentration for the ceramics is high, about 6%, and both the visible and invisible emissions are very strong. Among the emissions, the photoluminescence intensity of the red emission band increases most significantly by more than 47 times as the Er-concentration increases from 0.005 to 0.07. As a result, the Commission Internationale de L'Eclairage chromaticity coordinates shift from (0.29, 0.69) to (0.49, 0.50), and the emission color changes from green to yellowish green. Owing to the establishment of a dynamic circulatory energy process at high Er-concentrations, the photoluminescence intensity of the mid-infrared emission increases significantly by more than 4 times at the expense of the near-infrared emission. Together with the good ferroelectric and piezoelectric properties, the ceramics should be promising candidates for multifunctional optoelectronic applications.