Reversible yellow-gray photochromism in potassium-sodium niobate-based transparent ceramics

Ferroelectric ceramics exhibiting photochromic behavior and reversible luminescence modulation are highly desirable for optoelectronic applications ranging from information storage, displays, anti-counterfeiting to photo-switching devices. Herein, Sm3+-doped lead-free 0.85(K0.5Na0.5)NbO3-0.15SrZrO3 (KNN-SZ: Sm3+) transparent ferroelectric ceramic featuring a typical photochromic phenomenon is designed and demonstrated. Upon alternate illumination and thermal stimulus (220 ℃ for 1 min), the ceramic exhibits reversible yellow-gray coloration. Furthermore, a maximum relative reflectivity variation of 29 % and a large luminescence quenching of 65.4 % with superior fatigue resistance were achieved in KNN-SZ: Sm3+. Various in-situ illuminations and thermal treatments in different ambient conditions were carried out to bring insight into the trapping and de-trapping processes involved in photochromic behavior. The KNN-SZ: Sm3+ photochromic ceramics have great prospect in optoelectronic devices expanding the applications of KNN-SZ ceramics into advanced multifunctional materials for devices integration beyond electrical energy storage, electrocaloric and piezoelectric effects.