La₂O₃-Doped (K_0.5Na_0.5)NbO₃-Based Photochromic Transparent Ceramics for Optical Storage Applications

Good transparency and color contrast are difficult to obtain at the same time, which is a pressing problem for photochromic ceramics. Lanthanum oxide doping improved the transmittance and color-changing characteristics of the sample. In this study, the photochromism and reversible luminescence modulation of 0.94(K_0.5Na_0.5)NbO₃-0.06Sr(Bi_0.5Nb_0.5)O₃:2.0 wt% La³⁺ (KNN–SBN + La2.0) transparent ferroelectric ceramics with different sintering temperatures were investigated. KNN–SBN + La2.0 has good light transmittance and color contrast characteristics, as well as a certain degree of photoluminescence characteristics. The sample that was sintered at 1162°C has a relatively high dielectric constant (ε_r) and a high transmittance (1100 nm). The diffuse reflection spectra of the sample that was sintered at 1182°C has a wide absorption band at 400 nm, while, after ultraviolet irradiation, the reflectivity of the sample is significantly reduced. The color rendering rate of the sample at the sintering temperature of 1182°C is high, the color rendering contrast (ΔR_T) is 60.01%, and the high fluorescence luminescence contrast (ΔR_I) is 82.42% under 150 s of 365-nm light. Based on these results, KNN–SBN + La2.0 ceramics have a good application prospect in data storage and electronic goods.