Synthesis and magnetocaloric properties of La_(0.85)K_(0.15)MnO3 nanoparticles

摘要

In this paper, La_(0.85)K_(0.15)MnO3 nanoparticles were successfully synthesized at relatively low calcinated temperature from a polyaminocarboxylate complex precursor with diethylenetriaminepentaacetic acid (H5DTPA) as ligand, and the magnetocaloric properties were investigated. The phase transformation, chemical composition, and'microstructure of La_(0.85)K_(0.15)MnO3 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 La_(0.85)K_(0.15)MnO3 nanoparticles calcined at temperatures within the range of 600-1000 °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 La_(1-x)K_xMnO3 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 °C 800 °C and 1000 °C are 2.02,3.06 and 3.56/kg K at H = 2T, respectively. Also La_(0.85)K_(0.15)MnO3 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.