Electrical behavior of platinum-group metals in glass-forming oxide melts

This paper presents an experimental study of the electrical conduction mechanisms in glass-forming oxide melts containing RuO 2 needles. The composites were obtained by melting calcine in an industrial-scale induction-heated cold crucible melter. The temperature dependence of the conductance was measured by complex impedance spectroscopy, using a four-electrode cell, from 1200 °C to 400 °C. Direct current analysis revealed that even with low RuO 2 content, electronic and ionic transport occurred over a wide temperature range. The RuO 2 particle dispersion significantly enhances the total electrical conductivity up to 1200 °C. Percolation theory associated with tunneling conduction models is used to describe the electronic contribution to the conductivity. An equivalent circuit is proposed to describe the mixed ionic–electronic transport. The electronic conductivity not only depends on the RuO 2 content, but on the particle length-to-diameter ratio and the RuO 2 solubility.