Short communication Synthesis of La 0.7 Sr 0.3 MnO 3 at 800 8C using citrate gel method V. Ravi a, * , S.D. Kulkarni b , V. Samuel c , S.N. Kale d , J. Mona d , R. Rajgopal d , A. Daundkar d , P.S. Lahoti e , R.S. Joshee e a Physical and Materials Chemistry Division, National Chemical Laboratory, Pune 411008, India b Centre for Materials Characterization, National Chemical Laboratory, Pune 411008, India c Catalysis Division, National Chemical Laboratory, Pune 411008, India d Department of Computer Science, Fergusson College, Pune 411004, India e Department of Physics, Fergusson College, Pune 411004, India Received 22 December 2005; received in revised form 17 January 2006; accepted 13 February 2006 Available online 18 April 2006 Abstract Manganite systems have been of considerable interest in the recent past due to their potential to operate in wide property range and also to serve as effective magnetic sensing and storing devices when synthesized using stringent conditions. We report a novel citrate gel method, in which La 0.7 Sr 0.3 MnO 3 system has been synthesized at temperature 800 8C (LSMO800) with the synthesis duration is 6 h. The results have been compared with the sample synthesized at 1050 8C (LSMO1050). The synthesized bulk polycrystalline sample shows single-phase nature with the increase in particle size from 50 nm to 300 nm with the increase in the sintering temperature. The magnetization data for LSMO800 shows well-defined hysteresis with saturation magnetization at around 1800 Oe and Curie temperature at 360 K, which is slightly lower than that of LSMO1050, which is 375 K. The results can be well attributed to the grain boundary effects. # 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Ceramics; Oxides; CMR; Citrate gel method 1. Introduction Colossal magnetoresistive (CMR) materials are doped Mn- oxides with generalized formula as (R 1x M x )MnO 3 (where R = La, Nd like rare earth element and M is a divalent dopant such as Sr and Ca). These materials exhibit large magnetor- esistanc and have wide applications as magnetic sensors, hard disk read–write heads, infrared detectors and microwave based application [1–3]. The materials are of immense interest due their rich phase diagram, which indicate that their properties are highly dependent on the type of R and M and also on the value of x [4–6]. The parent compound (LaMnO 3 ) is an antiferro- magnetic insulator, while the hole doped manganites undergo metal–insulator transition and ferroparamagnetic transitions at T c and T p respectively, where T c is close to T p . By changing the doping concentration, the electrical and magnetic properties can be tuned as per the specific device requirement. There have also been reports on their wide range of properties, which depend on the grain size of the synthesized sample. After significant studies, it has been observed that if the manganite material consists of grain boundaries, the materials exhibit large magnetoresistance at sufficiently low magnetic fields [5,12]. Understanding of transport and magnetotransport properties in these materials is an appreciable challenge. Of all various kinds of manganite systems, La 1x Sr x MnO 3 (with x = 0.3) (LSMO) is one typical composition, which is of much interest due to its T c much above room temperature (350 K) and substantial magnetoresistance (MR) [4,7–9]. These materials have been around for almost a decade now, and various synthesis routes have been investigated to form these compounds in their bulk as well as thin film form. The magnetic and magneto-transport properties of these materials are highly sensitive to the synthesis route, pre- and post- synthesis annealing, calcinations and sintering temperatures, oxygen stoichiometry control, grain boundary engineering and so on. Synthesis time, temperature range, quality of the precursors used and consideration of their economical production viability at larger scale, are the major issues, which are to be worried about. Further, the sample synthesized should be homogeneous, with smaller particle size, compact and hard, www.elsevier.com/locate/ceramint Ceramics International 33 (2007) 1129–1132 * Corresponding author. Tel.: +91 20 5893300; fax: +91 20 5893044. E-mail address: r.venkat@ncl.res.in (V. Ravi). 0272-8842/$32.00 # 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2006.02.008