Influence of microstructure on the thermal conductivity of magnetoresistive La0.7Ca0.3MnO3/Mn3O4 manganite/insulating oxide polycrystalline bulk composites

摘要

We report the temperature dependence of the thermal conductivity kappa(T) of bulk polycrystalline composite samples containing a magnetoresistive manganite (La0.7Ca0.3MnO3) and an electrically insulating phase (Mn3O4). The sample porosity is shown to be a significant parameter affecting the experimental data: after porosity correction the curves display the characteristics of an ideal composite. A fit of the kappa(T) curves at low temperature using the Debye model enables the mean free path of phonons scattered on "boundaries" to be determined. The values are on the order of the grain size but are influenced by the grain arrangement and the presence of twins.