Resistivity of Selected Ceramics

Wayne, S. F., andBuljan, S. T., The Role of Thermal Shock on Wear Resistance of Selected Ceramic Cutting Tool Materials, Ceram. Eng. Sci. Proc., 9(9-10) 1395-1408 (1988)... 

Bennett, James P., Corrosion Resistance of Selected Ceramic Materials to Nitric Acid,... 

The conductivity of ceramic substrates is extremely low. In practice, it is primarily due to impurities and lattice defects, and may vary widely from batch to batch. The conductivity is also a strong function of temperature. As the temperature increases, the ratio of thermal to injected carriers increases. As a result, the conductivity increases, and the V-1 relationship follows Ohm s law more closely. Typical values of the resistivity of selected ceramic materials are presented in Table 4.11. 

Table 11.3 Atmospheric Corrosion Resistance of Selected Ceramics...

The corrosion resistance of selected Si3N4 ceramics in NaOH is given in Fig. 40. The attack by bases is less pronounced than by acids. The extent of corrosion increases with increasing temperature and concentration of the bases [524], Also, in bases the intergranular films are not attacked as strongly as the triple points. In NaOH solutions often a linear dependence of the weight loss on time is reported. Materials which are less stable in acids are more stable in bases. This can be explained by the stability of the grain boundary phase [510],... 

Ceramics are subject to the same general forms of corrosion as metals and the same factors of atmospheric corrosion that affect metals also affect ceramics. Table 11.2 lists the atmospheric corrosion resistance of selected glasses and Table 11.3 does likewise for other selected ceramics. 

Selection of fluoropolymers is an integral part of the overall material selection process. This implies that all the available materials such metals, ceramics, and plastics are considered candidates for an application. The end user then considers these materials against established criteria such as required life, mean time between inspection (MTBI), ease of fabrication, frequency of inspection, extent of maintenance and, of course, capital cost. More often than not it is the initial capital cost, rather than the life cycle cost of equipment, that affects the decision made during the material selection step. However, the most important piece of data is the corrosion resistance of a material in the medium under consideration over the life of the equipment. This information is available in a different format for plastics than for metals. A comparison is appropriate. 

Selecting ceramics for use at high temperatures or under applied load requires consideration of their long-term stability. Time dependent deformation is known as creep, and creep resistance is a critical design parameter. Even if creep does not lead to failure, a change in shape or size may render a component useless. The mechanism responsible for creep depends on temperature, stress, and the microstructure of the ceramic. 

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