Electrical properties of multicomponent CMM in correlation with their microstructure

In this work, electrical properties (resistance, resistance temperature coefficient, thermoelectric voltage, current–voltage curve) of multi-component ceramic matrix materials have been investigated. The influence of the structure of discrete particles on the microstructure and properties relations of CMM composites has been studied. Three groups of resistive materials were analyzed: (a) high resistance matrix and percolation clusters; (b) ionic or (c) covalent ceramic matrix and metal-like percolation clusters. The percolation threshold in composite materials is defined as the composition at which the conducting phase forms a continuous three-dimensional network through the material. However, in typical CMC we have observed a multi-threshold situation: at some content of conducting particles the first percolating clusters are formed; when the number of particles increases, clusters are destroyed to be created again at some higher content of conducting particles. These processes are strongly dependent on the starting materials properties, as well as on the thermal treatment of composites. Based on this approach a new product has been designed. Much attention was paid to the particulate structure and processing. A CMM with the resistance ratio R800/R20 = 1.4 has been manufactured. Intensive resistance growth begins at 700 °C and the maximum is achieved at 1100 °C.