High-resolution electrical characterization of RuO2-borosilicate glass composites

RuO2-borosilicate glass composites representing nuclear glasses show a sudden increase in electrical conductivity when the RuO2 content reached concentration of around 1% volume. This percolation threshold is astonishingly low compared to geometrical threshold, i.e. 15%, considering random distribution phases. Herein, electrostatic force microscopy (EFM) analyses were used investigate this anomalous behavior by performing local dielectric characterization that comprised clusters precipitated particles and "apparently” RuO2-free borosilicate regions. As expected, differences between relative permittivity two zones, matrix, particles, found. Most interesting, sensitivity EFM technique combined with numerical modeling based on finite element method revealed matrix was enhanced overall content. Such an can be explained enrichment RuO2, which increases due its much higher electronic polarizability. The could play role conduction mechanism, changing effective volume conductive medium and, therefore, decreasing minimal phase necessary for percolation.