How to Realize Ultrahigh Photochromic Performance for Real-Time Optical Recording in Transparent Ceramics

A combination of transparency and photochromic (PC) properties in ferroelectrics has promising application potential in smart windows and optical storage/imaging. Nonetheless, limited by understanding the underlying PC mechanism, a splendid PC performance is rarely achieved in transparent ferroelectrics. Here, a strategy to construct deep-lying traps by ion-doping induced defect engineering in (K_0.5Na_0.5)NbO₃-based ferroelectric ceramics is proposed. Based on the improved density functional theory simulations, a high concentration of vacancy defects can be realized by codoping 1 mol % Pr and 4 mol % Ba in (K_0.5Na_0.5)NbO₃, which helps achieving deep-lying traps and then superior PC performance. Through traditional pressureless sintering, highly transparent ceramics with designed optimal composition have been fabricated in a wide sintering temperature range (1170-1210 °C), exhibiting an ultrafast PC feature, i.e., 0.1 s response time (by illumination of 400 nm light), along with high PC efficiency (5.8 cm²·W^-1) and PC rate (7.1 s^-1), preeminent among reported inorganic PC transparent materials. Additionally, the ceramics have been utilized for real-time optical recording, displaying unambiguous patterning with long-time preservation (21 days). This research supplies a paradigm for designing high-performance PC transparent materials in optical applications and helps deepen the comprehensive understanding of the PC mechanism.