Sr/Ho-codoped (K0.5Na0.5)NbO3 photochromic-transparent ceramics in non-destructive optical data storage and multi-modal anti-counterfeiting†

Transparent-photochromic materials have garnered significant attention for their applications in optical information storage and anti-counterfeiting, which necessitate excellent transparency and high optical contrast. Herein, x mol% Sr²⁺ and 1 mol% Ho³⁺-codoped (K_0.5Na_0.5)NbO₃ (xSr–1Ho–KNN) ceramics were synthesized by a conventional solid-state reaction and pressureless sintering. Notably, the 7Sr–1Ho–KNN ceramic displays exceptional transmittance (60.7% at 780 nm), attributed to its fine grains and highly symmetric crystal structure. The photochromic (PC) contrast based on the change in photoluminescence (PL) intensity of 7Sr–1Ho–KNN under excitation with a 980 nm laser reaches as high as 91.5%. After thermal treatment under appropriate conditions, the transmittance and PL intensity of the ceramic can revert to their respective original values, demonstrating superior optical stability in response to alternating light and thermal stimuli. The combination of high transparency and PC contrast suggests that the xSr–1Ho–KNN ceramics have promising potential for optical information storage and optical anti-counterfeiting applications, which can guide the development of other KNN-based materials or even multifunctional luminescent ferroelectrics.