Effect of Sintering Time on the Crystallisation, Morphology, Structure, Electric, Magnetic and Magnetocaloric Properties of La0.80Ag0.20MnO3

Abstract

The effects of sintering time -(t(S)) on the morphology, structure and magnetic properties of -La0.80Ag0.20MnO3 manganite perovskite investigated. The main purpose of the study was to explore the possibility of increasing the magnetocaloric effect through tuning the magnetic transition temperature depending on the -t(S). -La0.80Ag0.20MnO3 manganite perovskites were prepared by the sol-gel route, and sintering was applied at 1000 degrees C with five different -t(S) (24, 36, 48, 60, 72 h) in the air atmosphere. The relationship between the -tS and the morphology is studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). -t(S) mainly affects grain size, the distribution of grains, the microstructure, and crystallinity. The crystal phase structure determination was carried out by x-ray diffraction (XRD) analysis. All samples have a characteristic perovskite structure, peaks of which indexed with the rhombohedral phase (R3c). XRD also reveals that all samples have a different ratio of metallic Ag and -MnO2 impurities. Temperature dependent resistivity measurement shows all samples have a metal-insulator phase transition around room temperature, -T-IM = 300 K. There seems to be no systematic change in the magnetic phase transition temperature (Curie temperature, -TC), and the magnetocaloric properties of the samples due to the increasing -t(S). The temperature dependence of the magnetization measurements exhibits a ferromagnetic to paramagnetic transition roughtly at 288 K. The maximum magnetic entropy change values were calculated to be around 2.43 J/kg K under a magnetic field change of 1 T.