Excellent optical transparency of potassium-sodium niobate-based lead-free relaxor ceramics induced by fine grains

Here we report a lead-free multifunctional material (1-x)(K0.5Na0.5)NbO3-xBa(Mg1/3Nb2/3)O-3 prepared by pressure-less sintering procedure. X-ray diffraction indicates a gradual crystal structure transformation with increasing x. Microstructural observation demonstrates that the addition of Ba(Mg1/3Nb2/3)O-3 additive reduces the size of grains with clear grain boundary, which is favorable for a high optical transmittance. The relaxor characteristics of the ceramics could lead to further enhancement of the transparency, owing to the low defects and weak light scattering. Notably, the ceramics with 0.04 <= x <= 0.06 all show good transparency over 70% in visible region and 80% in infrared region.