Reversible multi-mode modulations of optical behavior in photochromic-translucent Nd-doped K0.5Na0.5NbO3 ceramics

Abstract

A novel photochromic (PC) ferroelectric material, Nd³⁺-doped K_0.5Na_0.5NbO₃ translucent ceramic, was fabricated by a conventional solid method. The ceramic shows moderate optical transparency due to its dense microstructure, as well as good photoluminescence (PL) properties of up-conversion (UC) emission in the visible region and down-shifting (DS) emission in the near-infrared region. Simultaneously, the colors of all the ceramics turn darker after 365 nm illumination, and then recover to their initial states upon thermal stimulus (210 °C, 10 min), exhibiting a typical PC phenomenon. In particular, the effect of the PC behavior on PL lifetimes of Nd³⁺ was investigated. Multi-mode reversible modulations of various optical behaviors were realized based on the PC behavior, especially for the regulation of near-infrared emission. And the maximum modulation ratios of transmittances, UC or DS PL intensities and luminescence lifetimes are 43.0%, 66.7%, 66.4% and 12.8%, respectively. Owing to high-temperature sintering and Nd³⁺ substitution in the ceramics, cation and oxygen vacancies appear to produce F′ and V₁ color centers, which are in charge of the PC behavior and corresponding modulations. These results suggest that the ceramics are a promising PC material in visible and near-infrared optical data storage, photo-switches, and optoelectronic devices. Meanwhile, they also provide insights into the applications of rare-earth Nd³⁺ in other inorganic PC ferroelectric materials.