Ceramics are unique in their ability to interact with electric and magnetic fields, and exhibit properties that can vary many orders of magnitude. These include the dielectric permittivity, electrical conductivity, piezoelectricity, magnetic susceptibility, and magneto- and electro-optics. With this variety of properties, the use of ceramic components in electronics is so vast that it includes most of the devices and appliances which we encounter and use every day. For example, the electrical insulating properties allow for the use of materials such as alumina for substrates in integrated circuits as well as high voltage insulators (e.g. computers, spark plugs, TV). Electrical energy storage capabilities have allowed ceramic materials to be integral parts of electronic circuits which require both active component isolation as well as local power supplies which capacitors provide (e.g. TV, computers, cell phones). A high electronic conductivity allows ceramics to be used as electrodes as well as resistors for a wide range of applications. Piezoelectric properties allow ceramics to serve as transducers for many everyday applications (e.g. ultrasonic imaging and smoke detectors). And the ability of zirconia to display a high oxygen ion conductivity has enabled a rapidly growing list of applications such as oxygen sensors (every automobile has one), oxygen separations membranes and electrolytes for solid oxide fuel cells.
All of these applications of ceramics are perfect examples where understanding the structure-property relationships at multiple scale levels was a key necessity for success. And amongst the crystallographic symmetries which have yielded the most varied properties, the perovskite system reigns supreme. I have dedicated my research career to this system, exploring the influence of composition and defect structure on both insulating and conducting systems. I first will discuss the properties and characteristics of this unique class of ceramics which allows them to be utilized both as electrical insulators as well as electrical conductors. I will then give some examples in which the properties are tailored to meet requirements of specific applications: capacitors, solid oxide fuel cells, and sensors.
(Harlan Anderson is a Curators’ Professor of ceramic of engineering