Nanocomposite Ceramics on the Basis of Magnesium, Cerium, and Samarium Oxides

Abstract

A model of conductivity of nanocomposite ceramics consisting of solid-electrolyte and dielectric phases is proposed based on the assumption that the conductivity of grain boundaries between the solid-electrolyte and dielectric phases is higher than the conductivity of the volume of particles in the solid-electrolyte phase and its grain boundaries. Taking into account the size of particles, the thickness of grain boundaries, and the bulk and grain-boundary conductivities, the grain size of composite ceramics for which the conductivity may exceed the conductivity of single-phase solid-electrolyte ceramics is assessed. For testing this model, the composite samples are synthesized based on dielectric magnesium oxide and solid-electrolyte cerium oxide doped with samarium oxide. It is shown that introduction of 50 mol % magnesium oxide into composite ceramics has virtually no effect on its conductivity as compared with single-phase solid-electrolyte ceramics. This result can be explained by assuming the appearance of accelerated transport routes for oxygen ions in grain boundaries between dielectric and solid-electrolyte phases. Further dispersion, optimization of the ratio, and increase in distribution homogeneity of components can confirm the validity of the proposed conductivity model and open up the possibility of preparation of oxide solid-electrolyte materials with higher conductivity.