Abstract
Vanadium oxides (V2O5) with relatively low melting point (963 K) was found to be an effective sintering aid for forming multiphase nanocomposite of La2/3Ca1/3MnO3. The polycrystalline perovskites with a nominal composition of La2/3Ca1/3Mn1−xVxO3 (0 ≤ x ≤ 0.12) were prepared by the liquid-phase sintering method. The structure, magnetic properties and magnetocaloric effect (MCE) were investigated. The study on microstructure revealed that the composites consist of a major crystalline phase of La2/3 Ca1/3MnO3 and intergranular phases of Ca10V6O25 and La2MnO4.15 at the grain boundary. All the samples undergo the first-order phase transition at the Curie temperature. V-addition leads to a reduction of the Curie temperature, but significantly improves the MCE. The maximal magnetic entropy change of 3.8 J/kg K was achieved for x = 0.08 under an applied field of 0.5 T, almost twice as high as the un-doped sample. The result implies that the control of intergranular phases is a potential way to improve the MCE in perovskite manganites. The enhancement of MCE could be attributed to spin-polarized tunneling or spin-dependent scattering of polarized electrons at the grain boundaries.
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