KSr₂Nb₅O₁₅-based composite ceramics: The atomic-scale anisotropic origin of photochromism and influences of second phase concentrations on optical properties

The compositing modification strategy overcame the contradiction between the concentration and depth of photochromic centers and effectively enhanced the photochromic and luminescence modulation abilities of KSr₂Nb₅O₁₅-based ceramics. However, the compositing concentration influences and potential competitive mechanism are unclear. In this work, the influences of Nb₂O₅ composite concentration on the microstructures and the photochromic and luminescence modulation properties were systematically investigated. The overconcentration generated the aggregation of the second phase, which brought the competitive mechanism during the photochromic reaction and deteriorated the property. Moreover, to further strengthen the anti-counterfeiting ability, the textured composite ceramic was prepared by a template grain growth method. In addition to the grain-oriented microstructures and anisotropic optical properties, an atomic-scale explanation of the anisotropies of the defect distribution around interfaces was given. This work further explores the heterojunction modification mechanism and the atomic-scale origin of anisotropic photochromism and paves the way to develop and modify photochromic ceramics by interface design.