Microstructure and electrical resistivity of calcined magnesite

The high-temperature electrical resistivity of magnesia powders derived from natural magnesite was investigated. These powders are currently used as electrical insulation in mineral insulated cables, produced in Australia by Pyrotenax Australia Pty Ltd. Heat Containment Industries Pty Ltd are the principal suppliers of calcined magnesite to Pyrotenax Australia Pty Ltd. The insulative characteristics of the calcined magnesite varies from source to source and are dependent on mineralogical parameters and the industrial processing (i.e. calcining conditions). Magnesite materials from two different mines proved to have significantly different electrical resistivity as measured in short cable sections.