Unraveling theRole of F‑Type Color Centerson the Optical and Electrical Properties of Al₂W₃O₁₂ Nanoparticles with Different Content of Oxygen Vacancies

Identification and tuning of defects in nanomaterials are critical to the advancement of emerging technologies. In this work, F-type color centers in Al₂W₃O₁₂ nanopowders, formed via extrinsic oxygen vacancies, were comprehensively studied for the first time. By correlating photoluminescence (PL), electron paramagnetic resonance (EPR), and diffuse reflectance spectroscopy (DRS), the types of F color centers were identified, unraveling their influence on the optical and electrical properties of Al₂W₃O₁₂ nanopowders. EPR coupled with X-ray photoelectron spectroscopy (XPS) demonstrated that the formation of F-type color centers in Al₂W₃O₁₂ nanopowders is mainly generated by an electronic charge compensation process. Our experimental findings highlighted that the increased concentration of F and F⁺ color centers, present in the heat-treated Al₂W₃O₁₂ nanopowders under inert and reducing atmospheres, contributed to enhanced visible light sensitivity and higher electrical conductivity due to the introduction of intermediate energy levels within the band gap by the F-type color centers, the contribution of free electrons from the formation of F⁺ color centers, and the excitation of trapped electrons in the F⁺ and F color centers to the conduction band. These findings provide new insights into the creation and tuning of F-type color centers in nanomaterials, potentially enabling applications in advanced technological devices.