Synthesis and characterization of (1 − x)(La_0.6Ca_0.4MnO₃)/x(Sb₂O₃) ceramic composites

ABSTRACT

The composites ((1 − x)(La_0.6Ca_0.4MnO₃)/x(Sb₂O₃)) (x = 0.00, 0.07 and 0.12) were synthesized by conventional solid-state reaction method. The results of X-ray diffraction (XRD) and SEM indicate that Sb₂O₃ and LCMO coexist in the composites and Sb₂O₃ mainly segregates at the grain boundaries of LCMO. Furthermore, the magnetic study shows a typical variation. The resistivity of the composite samples was measured at the applied magnetic fields of 0T, 2T and 5T. All the specimens undergo a metallic–semiconductor transition at the temperature T_ρ. The temperature dependence of resistivity shows that the transport behavior of the composites is governed by the grain boundaries. It is suggested that the Sb₂O₃ addition, acts as a separation layer between grains. The ρ-T fit well with the phenomenological equation for conductivity under a percolation approach. Magnetoresistance (MR) has been found to reach a maximum value with Sb₂O₃ addition. The magnetocaloric properties of LCMO based on resistivity measurements were investigated. We measure the magnetic entropy change ΔS_M from the resistivity which is similar to that calculated from the magnetic measurements. Finally, the TCR curves show good value under zero magnetic field, which makes it a good candidate for bolometer applications.

KEYWORDS:

• Manganite-composite
• resistivity
• percolation model
• TCR
• MR