Structural, Optical, Thermal and Photocatalytic Dye Degradation Properties of BiFeO 3 –WO 3 Nanocomposites YATHAVAN SUBRAMANIAN, 1 VENKATAPATHY RAMASAMY, 1 RAMESH KUMAR GUBENDIRAN, 1,4 GOKUL RAJ SRINIVASAN, 2 and DURAIRAJAN ARULMOZHI 3 1.—Department of Physics, University College of Engineering Arni, Anna University, Arni, India. 2.—Department of Physics, C. Kandaswami Naidu College for Men, Chennai, India. 3.—I3N- Aveiro, Department of Physics, University of Aveiro, Aveiro, Portugal. 4.—e-mail: rameshvandhai@gmail.com In the present work, nanocomposites of BiFeO 3 –WO 3 (BFO–WO 3 ) have been successfully synthesized for the first time by a single step sol–gel method. The main objective lies in enhancing the photocatalytic activity of BiFeO 3 by modifying it with a WO 3 matrix. Powder x-ray diffraction studies on BFO– WO 3 confirm the presence of the monoclinic character of WO 3 along with rhombohedral BFO. In addition, elemental mapping using energy dispersive x-ray analysis ascertains the existence of tungsten ions in the BFO matrix. Field emission scanning electron microscopy analysis on pure and nanocom- posites depicts the distinct morphologies of the nanoparticles upon modifica- tion of BFO with WO 3 . From the UV–Vis–NIR spectrum, it has been noticed that there is a reduction in the band gap energy from 1.8 eV (BFO) to 1.5 eV (BFO–WO 3 ) suggesting the increase in the absorption of a visible portion of light upon loading of WO 3 in BFO. Thermogravimetric analysis/differential thermal analysis trace of BFO–WO 3 nanocomposites shows that there is a suppression of the multiferroic character of BiFeO 3 , when it is modified with WO 3 . However, the photodegradation of methylene blue using BFO–WO 3 nanoparticles found to have been enhanced to 91%. The increase in dye re- moval property may be due to the fact that the higher surface area of nano- composites due to the incorporation of WO 3 particles. The other significant results have been discussed in detail. Key words: Methylene blue, dye degradation, nanocomposites INTRODUCTION Recently, semiconductor photocatalysts have been given considerable attention among the scien- tific community due to their property of complete decomposition of the harmful pollutants from usable water resources and solar energy. 1 As solar light can be a potential energy source for photocatalytic degradation, initial researches on the semiconduc- tor based photocatalysis were focused mainly on wide band gap semiconductors like TiO 2 , titanates, etc., using UV light, and it was observed by Fuishima and Honda 2 owing to their high stability, low cost, and nontoxicity. However, their applica- tion in photocatalysis under visible light is limited, consequent to their large band gap energy of 3.0– 3.4 eV, which could activate only the UV portion of light. 3–6 Many attempts, including doping with metals and/or nonmetals, attaching dye molecules as the photosensitizers, were found to have been carried out to make them visible light active. 7 But, it has ended up with limited success. In case of doping with metals and/or nonmetals, extending the light absorption towards the visible region was too little and interband doping states act as the source of recombination centers for the photogenerated (Received June 7, 2018; accepted September 6, 2018) Journal of ELECTRONIC MATERIALS https://doi.org/10.1007/s11664-018-6654-2 Ó 2018 The Minerals, Metals & Materials Society