OXYGEN-ION COMPOSITES MWO4-SiO2 (M – Sr, Ba)

Abstract

Composite materials (1-f)SrWO4–fSiO2 and (1–f)BaWO4–fSiO2, where f is the volume fraction of the dispersed SiO2 additive, were prepared by the solid-phase method. The resulting composites were studied by XPA, TG-DSC, SEM-EDA. The electrical conductivity of the composites was measured by the electrochemical impedance method as a function of temperature, oxygen partial pressure in the gas phase, and composition. To estimate the contribution of ionic conductivity, the sum of ionic transfer numbers was measured by the EMF method. It has been shown that the addition of 20–25 vol % nano-SiO2 to low-conductivity oxygen-ion conductors SrWO4 and BaWO4 leads to an increase in the ionic conductivity of composites based on them by two orders of magnitude and by 12 times, respectively. The increase in conductivity in the systems under study is explained by the additional contribution of interfacial boundaries formed between the MeWO4 matrix and dispersoid nanoparticles. The mixing rule [1] was used to calculate the electrical conductivity of (1-f)SrWO4–fSiO2 and (1-f)BaWO4–fSiO2 composites depending on the SiO2 content. The calculated concentration dependences of the conductivity obtained are in satisfactory agreement with the experimental results.