Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Characterization of perovskite LaFeO 3 synthesized by microwave plasma method for photocatalytic applications Orawan Wiranwetchayan a,c, ⁎ , Surin Promnopas a,f , Surachet Phadungdhitidhada a , Anukorn Phuruangrat e , Titipun Thongtem b,d , Pisith Singjai a,c,d , Somchai Thongtem a,d, ⁎ a Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand b Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand c Research Center in Physics and Astronomy, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand d Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand e Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand f The Graduate School, Chiang Mai University, Chiang Mai 50200, Thailand ARTICLE INFO Keywords: LaFeO 3 Microwave plasma Photocatalysis ABSTRACT Perovskite LaFeO 3 nanoparticles were successfully synthesized by microwave plasma method combined with high temperature calcination at 700–1000 °C. The influences of calcination temperature on morphology, crys- talline structure, purity and the atomic compositions of samples were studied. The photocatalytic performance of LaFeO 3 was evaluated though the photodegradation of Rhodamine B (RhB) under visible light. In this research, the orthorhombic LaFeO 3 nanoparticles showed band gaps in the range of 2.15–2.30 eV. The particle size in- creased with increasing in the calcination temperature, leading to the decreasing in the surface area. The LaFeO 3 sample calcined at 900 °C showed the highest photodegradation of 77.8% and the apparent rate constant of 0.0077 min -1 within 180 min because of the narrower of band gap and the higher crystalline degree and oxygen adsorption. 1. Introduction For industries, photocatalysis is one of the best processes for en- vironmental purification because it is a clean approach and usage of ultraviolet–visible light. Photocatalytic reactions involve photogenera- tion of electron-hole pairs through the absorption of solar energy; and reduction/oxidation reactions occur [1]. Heterogeneous photocatalysis via semiconducting oxides such as TiO 2 , WO 3 and ZnO and non-oxides such as CdS and Ta 3 N 5 is considered as the main catalyst for degrada- tion of organic pollutants in air and water. However, the photocatalytic efficiency of these materials is still limited. With respect to these issues, perovskite-type oxide materials have attracted considerable attention for use as photocatalysts to decompose toxic organic compounds. Per- ovskite-type oxides have general formula of ABO 3 , where A is the rare earth ion and B is the transition metal ion. Lanthanum ferrite (LaFeO 3 ) perovskite is an important p-type semiconductor with excellent physical and chemical properties. It has been applied in advanced applications such as electrode material in solid oxide fuel cells [2], sensors [3,4], and catalysts [5–8]. Moreover, LaFeO 3 has orthorhombic perovskite structure with antiferromagnetic properties [9,10]. Its properties make these materials appropriate for data storage. Generally, the properties of LaFeO 3 are strongly influenced by the synthetic method, and they allow for adjustment of their crystalline structure, electrochemical performance, morphology, and size distribution. Several methods were used to synthesize LaFeO 3 , including the sol–gel method [3,4], hydro- thermal process [11], electrospinning [12], and microwave-assisted method [13]. In recent years, several research groups have used the microwave plasma method for the synthesis of semiconducting particles. Microwave is an electromagnetic wave with frequency ranging between 300 MHz and 300 GHz, and the photonic energy ranging from 1.24 meV to 1.24 μeV. When microwave is radiated onto the precursor, the mi- crowave power is absorbed. The distribution of charge within the precursor molecules is created, and is assymmetrical. Therefore, the temperature of the precursor increases due to the occurrence of dipolar polarization or interfacial polarization [14]. These molecules rotate according to the electric field oscillation. Ionization and dissociation occur when the electric field of the microwave is strong enough to break down bonding of the molecules/atoms, and plasma generates. This ionization and dissociation can initiate and enhance the kinetics of https://doi.org/10.1016/j.ceramint.2018.11.175 Received 12 September 2018; Received in revised form 22 November 2018; Accepted 22 November 2018 ⁎ Corresponding authors at: Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand E-mail addresses: wiranwetchayn@gmail.com (O. Wiranwetchayan), schthongtem@yahoo.com (S. Thongtem). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2018 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: Wiranwetchayan, O., Ceramics International, https://doi.org/10.1016/j.ceramint.2018.11.175