Photochromic (PC) luminescent ferroelectric materials have aroused great interest because of their potential applications in non-contact smart information storage materials and devices. In this work, we adopted the effect of...

Ferroelectric photo‐thermochromic (PTC) materials with both high coloration contrast and high transparency have attracted great attention for their applications in “smart window” for non‐contact optical information storage. Nevertheless, it has been challenging to develop a ferroelectric PTC material that simultaneously meets the distinct transparency and coloration contrast requirements. Herein, dual rare‐earth ions doping of 1%Er‐(K0.5Na0.5)0.985La0.015NbO6 (Er‐KNLN) ferroelectric ceramics is aimed at increasing the optical transmittance and obtaining an ideal coloration contrast. The traditional solid‐state reaction is exploited for ceramics fabrication, and the optimal optical transmittance (≈70% at 900 nm) can be obtained due to finer grains, more symmetrical structure, and compact structure in samples sintered at a suitable temperature (such as ≤1165 °C). Contributed from the trapping and de‐trapping of charge carriers in vacancy‐related defects, the Er‐KNLN ceramics exhibit obvious PTC behavior and the novel impedance modulation is developed. The coupling between PTC behavior and optical transparency, lanthanide up‐conversion emission, patterned display, and room temperature impedance enables nondestructive rewritable and readout characteristics of multi‐mode “0” and “1” states. This work solves the main problems hampering the promising applications of ferroelectric materials and paves a way for developing multifunctional optical memory smart windows.

An up-conversion luminescence (UCL) transparent ferroelectric oxide (KNN) introduced by rare-earth ions (Er3+ and Bi3+) has been demonstrated to exhibit a unique, high-purity, red emitting, high transparency, reversible, photothermochromic (PTC) reaction. And, its associated transmittance/red emitting modulations are realized via the continuous alternating of UV light irradiation and heat treatment (200 °C). The effects of the phase structure, microstructure, and oxygen vacancy defects on their optical transmittances and the corresponding optical modulation based on PTC reaction at different sintering temperatures were systematically studied. Because of the sufficiently small grain size, dense structure, and appropriate concentration of oxygen vacancy defects, excellent optical transparency (∼70%, at 900 nm) and moderate PTC modulation contrast (ΔAbs = 13.9%, ΔR = 48.9%) are obtained in KNNEB-1155. The decreased and increased transmittance/red emitting can represent two pairs of “off” and “on” codes, which makes the red-emitting KNNEB transparent ceramics very competitive in the application of multifunctional transparent sustainable warning equipment and optical storage materials.

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