Temperature‐controlled synthesis of bismuth tungstate with enhanced photochromic properties

İngilizce (OpenAlex)

Abstract This study explores the photochromic properties of bismuth tungstate (Bi2WO6) synthesized via a solid‐state method at various temperatures (300°C–1000°C) to optimize light‐responsive behavior for potential applications. The Bi2WO6 samples, prepared from tungsten oxide (WO3) and bismuth oxide (Bi2O3) through heat treatment, were analyzed using X‐ray diffraction (XRD), UV‐Vis Diffuse Reflectance Spectroscopy (UV‐DRS), and scanning electron microscopy (SEM) techniques. XRD results revealed the formation of the Bi2WO6 phase at higher temperatures, while the Bi14W2O27 phase, formed at 400°C–500°C, exhibited an oxygen‐deficient structure enabling significant color shifts. Band gap analysis showed that samples synthesized at 400°C and 500°C had a lower band gap (2.63 eV) compared to those prepared at higher temperatures, suggesting enhanced electronic properties due to oxygen vacancies. SEM images showed nanoscale crystal facets in the 400°C and 500°C samples, which facilitated effective sunlight excitation and stable color changes. Under sunlight exposure, these samples transitioned from yellow to greenish brown within 5 min, quickly reaching color saturation, while samples synthesized at higher temperatures showed minimal photochromic response. This work is the first to report on the photochromic properties of Bi2WO6 synthesized through solid‐state methods, highlighting the role of oxygen vacancies, reduced band gap, and nanoscale morphology on enhancing photochromic performance.