Electrical Conductivities of Conductors, Semiconductors, and Their Mixtures at Elevated Temperatures

Modernization efforts across the energy and industrial sectors are driving developments in engineered materials with tailored electrical properties suitable for operation in demanding thermal environments. The nominal electrical properties of common material classes, including metals, semiconductors, and insulators, are well‐known and routinely measured by researchers in materials science, geophysics, engineering, and physics. Despite decades of study, a persistent conductivity gap exists between metals and semiconductors at elevated temperatures. In this article, experimental data from the literature are reviewed to provide the first summary of the electrical properties of metals, semiconductors, and some insulators under direct‐current conditions at elevated temperatures, further highlighting the existing conductivity gap between these material classes. To bridge this gap, metal‐ceramic irregular metamaterials (MCiM) are proposed as novel engineered composites containing high‐ and low‐conductivity granular materials identified from the literature. The bulk electrical conductivity that emerges from the MCiM as a function of material constituents, relative volume fraction, and temperature is modeled with an effective medium approximation. MCiM mixtures composed of Cu/Cu 2 O, Cu/MgO, and Ni/Cu 2 O are predicted to span the conductivity gap between and S/m. In comparison to current materials exhibiting a negative temperature coefficient of resistivity, MCiM offers a low‐cost alternative for high‐temperature applications where tailored electrical properties are required. Opportunities for future research focusing on characterizing the temperature‐dependent conductivities of commercially available metal and ceramic powders to experimentally validate the MCiM concept are discussed.