Effects of processing parameters on the properties of lanthanum manganite

A systematic study of the effects of processing parameters on the structure, microstructure, magnetic, and magnetotransport properties of lanthanum manganite (LMO) ceramics are presented. LMO ceramics are prepared using solid-state reaction technique by applying wide range of sintering temperatures 1100–1500 °C with varying holding times. It is observed that phase pure LMO can be formed at a sintering temperature of 1300 °C for a short duration of 2 h with measured density 4.8 g cm−3. Density does not improve with lower sintering temperature and longer duration. The grains appeared are quite homogeneous and uniform and do not differ much with further increase of temperature, however, less voids and higher leakage currents are observed for the LMO samples sintered at higher temperature. As the physical properties of manganites depend of structure, composition and oxidation states of Mn ions, XPS analysis are done to study the valence states. XPS analysis shows that LMO ceramics sintered at higher temperature have lower Mn valence and values approaches towards +2 as well as the loss of oxygen stoichiometry. All the samples show colossal magnetoresistance (CMR) behavior, however, the LMO prepared by sintering at 1300 °C for 2 h shows the highest MR% ∼60%.