Synthesis and magnetocaloric properties of La0.85K0.15MnO3 nanoparticles

In this paper, La0.85K0.15MnO3 nanoparticles were successfully synthesized at relatively low calcinated temperature from a polyaminocarboxylate complex precursor with diethylenetriaminepentaacetic acid (H(5)DTPA) as ligand, and the magnetocaloric properties were investigated. The phase transformation, chemical composition, and microstructure of La0.85K0.15MnO3 nanoparticles were characterized by X-ray diffraction (XRD), thermogravimetric (TG), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and electron diffraction (ED). The results revealed that La0.85K0.15MnO3 nanoparticles calcined at temperatures within the range of 600-1000 degrees C are of pure single-phase rhombohedral structure and the grain sizes were precisely controlled by varing the calcined temperature. The relationship between magnetocaloric properties and the calcined temperature of La1-xKxMnO3 nanoparticles was also investigated systematically. From the magnetic measurements as function of temperature and magnetic applied field, we have discovered that the Curie temperature T-C is 274.5 K and is independent of the calcined temperature. From the measurements and calculation of isothermal magnetization at different temperatures, the maximum magneticentropy changes close to T-C (274 K) of the samples calcined at 600 degrees C, 800 degrees C and 1000 degrees C are 2.02, 3.06 and 3.56/kg K at H = 2T, respectively. Also La0.85K0.15MnO3 nano-particle displays a second-order phase transition. These results suggest that this material is a candidate for use as an active for magnetic refrigerent around the room temperature. (C) 2010 The Society of Powder Technology Japan. Published by Elsevier B.A. and The Society of Powder Technology Japan. All rights reserved.