Photochromic and photoluminescence modulation properties of Zr6Nb2O17 ceramics doped with a variety of rare earth ions

Inorganic photochromic (PC) materials are increasingly recognized as promising candidates for anti-counterfeiting technologies and optical storage applications. To enhance their practical value, integrating superior mechanical properties can improve durability, ensuring stable performance over extended periods of use. In this study, we synthesized Zr₆Nb₂O₁₇-based structural–functional integrated ceramics doped with rare earth ions (Sm³⁺, Eu³⁺, Dy³⁺, and Ho³⁺) using the high-temperature solid-state reaction method. By controlling the excitation energy of luminescent centers, we regulated the photochromic contrast and photoluminescence modulation ratio of the materials. The results showed that, upon irradiation with 365 nm UV light, all prepared ceramic samples exhibited a significant deepening in color. The photochromic contrasts of the four types of rare earth ion-doped Zr₆Nb₂O₁₇ ceramics were 20.4% (Sm³⁺), 20.3% (Eu³⁺), 19.5% (Dy³⁺), and 20.0% (Ho³⁺), significantly higher than the undoped matrix's contrast of 12.4%. After heating at 350 °C, the colors of the ceramics were restored. Even after eight coloring–bleaching cycles, the color-changing performance remained stable, demonstrating excellent cycling stability and reversibility. Fluorescence modulation based on photochromic reactions effectively controlled the luminescence intensity of the rare earth ions, with luminescence modulation ratios of 39.7% (Sm₂O₃), 62.9% (Eu₂O₃), 61.2% (Dy₂O₃), and 41.3% (Ho₂O₃). The Vickers hardness values of different compositions ranged from 14.66 to 15.90 GPa, while the fracture toughness values ranged between 4.66 and 4.98 MPa m^1/2. All ceramic materials exhibited excellent cycling stability, reversibility, and rapid photoresponse times, indicating significant potential for applications in optical information storage.