A 3D Decoding Anti‐Counterfeiting Platform Based on Defect‐Engineered Photo‐Thermochromic Ceramics

ABSTRACT To address the urgent demand for materials that combine high stability, multifunctional response, and spatial encoding capabilities in the fields of 3D optical information storage and dynamic anti‐counterfeiting, the development of novel intelligent optical materials holds significant importance. Here, KNN‐based lead‐free ceramics were employed, achieving unique microstructural evolution and the formation of high‐concentration color centers through synergistic manipulation of composition and sintering atmosphere. The resultant 0.5Er@Defect ceramic not only exhibits transparency, but the abundant vacancy related defects formed in the matrix constitute an efficient photo‐thermochromic (PTC) multimodal optical modulation platform. Leveraging the photochromic (PC) behavior, it achieves an optical transmittance modulation degree (Δ Abs ) of up to 46.6% in the visible region while simultaneously exhibiting over 88% photoluminescence quenching contrast (Δ R ) for the characteristic upconversion luminescence of Er 3+ , rendering its exceptional comprehensive optical modulation performance highly competitive among currently reported inorganic PC materials. This promisingly enables the synchronous writing of three types of information within a single physical storage unit: color information for public display, transmittance information for efficient reading, and fluorescence information for core‐level confidentiality, realizing an intelligent secure storage architecture characterized by “single‐write, multi‐layer read” capability. This work not only elucidates the mechanism underlying the regulation of macroscopic optical properties through defect chemistry, but also provides novel insights for advancing dynamic anti‐counterfeiting and high‐capacity 3D optical storage technologies.