Correlation between the Electrical Properties and Structural and Morphological Characteristics of Samples in the Ba2In2O5–Ba2InNbO6 Quasi-Binary Eutectic System

The structural and morphological properties of samples in the Ba2In2O5–Ba2InNbO6 eutectic system were studied when treated below and above the eutectic temperature. A narrow-extent Ba2In2-xNbxO5+x (х ≤ 0.05) solid solution and (1 − y)Ba2In1.95Nb0.05O5.05∙yBa2InNbO6 composites were found in the system. In the y ≥ 0.15 composites, the major phase is a stabilized structure with a disordered arrangement of oxygen vacancies. The total electrical conductivity in dry air is determined primarily by oxygen-ion transfer, and it increases for both the solid solution and the composites; the greatest increase of about two orders of magnitude is in the y = 0.15 and 0.25 composite samples treated at above-eutectic temperature. The increase in electrical conductivity is due to the combined influence of structural and morphological factors. The composites treated at above-eutectic temperature have a specific morphology. A layer of submicron-sized crystallites is formed on the surface of the grains of the major phase upon eutectic crystallization, which is responsible for the appearance of the composite electrical conductivity effect.