Mid-IR to visible photoluminescence, dielectric, and ferroelectric properties of Er-doped KNLN ceramics

Two mole percentage Er-doped (K0.5Na0.5)1 - xLixNbO3ceramics have been prepared and their dielectric, ferroelectric, and photoluminescence (PL) properties have been investigated. Under an excitation of 980 nm, the ceramics exhibit intense up-conversion luminescent emission at 548 nm (green), weak emission at 660 nm (red) as well as strong down-conversion luminescent emission in near-infrared (NIR) (1.40-1.65 μm) and mid-infrared (2.60-2.85 μm) regions. Probably due to the induced structure distortion and reduced local symmetry, the PL intensities of the green, red as well as mid-infrared emissions are enhanced by the doping of Li+. Our results show that the Li-doping is effective in establishing a dynamic circulatory energy process to further enhance the PL intensity of the mid-infrared emission at the expense of the NIR emission. At the optimum doping level of Li+(∼6 mol%), the full bandwidth at half maximum of the mid-infrared emission reaches a very large value of ∼250 nm. The ceramics also exhibit good ferroelectric properties, and thus they should have great potential for multifunctional optoelectronic applications.