Short communication Sol–gel based Pechini method synthesis and characterization of Sm 1 - x Ca x FeO 3 perovskite 0.1 ≤ x ≤ 0.5 A.M. Huízar-Félix, T. Hernández ⁎, S. de la Parra, J. Ibarra, B. Kharisov Laboratorio de Materiales I, Centro de Laboratorios Especializados, Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, Ciudad Universitaria, Av. Pedro de Alba S/N, C.P. 66450, San Nicolás de los Garza, Nuevo León, México abstract article info Article history: Received 26 August 2011 Received in revised form 6 June 2012 Accepted 29 June 2012 Available online 6 July 2012 Keywords: Sol–gel method Perovskite-based compounds Calcium Iron X-ray powder diffraction This study initiates the preparation of Sm 1-x Ca x FeO 3 (0.1 ≤x ≤0.5) compounds by sol–gel based Pechini method at low temperatures. The samples are analyzed by X-ray diffraction (XRD), Scanning Electron Micros- copy (SEM), Thermogravimetric Analysis (TGA), and Differential Thermal Analysis (DTA) techniques for ap- propriate characterization of the distinct thermal events occurring during synthesis. The resulting XRD data reveal that a pure phase with perovskite structure is obtained for each composition. An exothermic peak ap- pears in the DTA curve at 700 °C for x = 0.1 sample, suggesting a crystallization process; a similar behavior is found to occur for the other compositions as well. The microstructural characteristics of all the phases show particles of different morphology and size. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Perovskite-related rare earth orthoferrites have attracted interest owing to their potential for use as logic- or memory-component devices and as laser and light modulators in optical materials [1,2]. In addition, the solids are catalytically active [3–5] and can be used as gas-sensing [6,7] and solid electrolytes [8–10]. In the past decades various methods have been studied for the prep- aration of perovskites oxides. The ceramic method has been one of the most commonly used; however, soft chemistry (Chemie Douce) routes of preparation such as sol–gel [11] prove to be a convenient alternative way to obtain inorganic materials. Table 1 shows a comparison of differ- ent advanced powder synthesis routes [12,13]. The resulting materials obtained by these methods exhibit a considerably smaller particle size and high porosity, as compared with those synthesized by the ceramic method. Further, soft chemistry methods also provide a better control on stoichiometry and reduce the synthesis temperature of materials [21]. Thus, variations on the sol–gel based Pechini method [22] have been employed in the successful preparation of several types of perov- skite materials. Pechini's method employs complexing of cations in an aqueous-organic medium and makes use of low cost precursors resulting in a homogeneous ion distribution at the molecular level. It is based on the fact that certain α-hydroxycarboxylic organic acids can form stable chelates with several cations. After the addition of a polyhydroxylic alcohol to this mixture, it is heated and the chelate is transformed into a polymer with a homogeneous distribution of cat- ions. The organic part is subsequently eliminated at temperatures as low as 300 °C, thereby forming reactive oxides. In particular, the samar- ium–calcium orthoferrites (0.1 ≤ x ≤0.7) have been synthesized for the first time in air by the solid state reaction and analyzed from a classical crystal chemistry point of view [23]. X-ray diffraction analysis on these samples indicates that these compounds are one-phase perovskite-type belonging to the Pbnm space group. The present study is aimed at de- scribing the synthesis of samarium and calcium orthoferrites (Sm 1- x Ca x FeO 3-y ) with x=0.1, 0.2, 0.3, 0.4, 0.5 by the Pechini method. The X-ray results indicate that all samples consist of one-single phase. Nev- ertheless, no report is available until now regarding synthesis of this system by this method. 2. Experimental 2.1. Preparation of Sm 1 -x Ca x FeO 3 (0.1 ≤ x ≤ 0.5) system Fig. 1 depicts the scheme for the synthesis of samarium–calcium orthoferrites. Polycrystalline powders of Sm 1-x Ca x FeO 3 (0.1 ≤ x ≤0.5) compounds were prepared under identical conditions via the sol–gel based Pechini method. Stoichiometric amounts of analytical grade Ca(NO 3 ) 2 • 4H 2 O, Sm(NO 3 ) 3 • 6H 2 O, Fe(C 2 H 3 O 2 ) 2 were dissolved in a cit- ric acid solution to which ethylene glycol and diluted nitric acid were added. The gel obtained was dried at 120 °C in a sand bath to obtain a resin, and this resin was then fired at 400 °C for 24 h in air. A powder was then obtained after a subsequent heat treatment. This powder Powder Technology 229 (2012) 290–293 ⁎ Corresponding author. E-mail addresses: tomas.hernandezgr@uanl.edu.mx, thernang@yahoo.com (T. Hernández). 0032-5910/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.powtec.2012.06.057 Contents lists available at SciVerse ScienceDirect Powder Technology journal homepage: www.elsevier.com/locate/powtec