Simultaneously improved transparency, photochromic contrast and Curie temperature via rare earth ion modification in KNN-based ceramics

Photochromic (PC) luminescent ferroelectric materials have aroused great interest because of their potential applications in non-contact smart information storage materials and devices. In this study, we adopted the effect of rare-earth ions to refine the grains, combined with the unequal replacement of donor doping and higher temperature sintering methods to introduce more vacancy defects, to simultaneously improve the transmittance and photochromic contrast of KNNLB-RE ceramics. The optical transmittance of a typical KNNLB-RE > 50%, and the modulation contrast of KNNLB-RE is relatively significant, such as ΔAbs = 16.2% and ΔR = ∼34% for KNNLB-Er. More interestingly, the Tc of KNNLB-RE increased by about 10%–18% (∼30 °C–50 °C) due to the degradation of the relaxor-feature and the increase of internal stress, which broadens the temperature application range of KNNLB-RE ferroelectric ceramics. In contrast to most opaque inorganic photochromic materials, the KNNLB-RE transparent ceramics can express multiple pairs of “off” and “on” codes by using the reversibly decreased and increased transmittance and PL intensity; thus, these materials have potential in the applications of optical sensors and memories or other optical data storage devices.