A perfect dielectric is a material in which there are no free electrical charges, and which therefore does not conduct electricity. Real dielectrics, also known as insulators, are never perfectly insulating, with the result that there has been a 150-year search for ever better dielectric materials.

The first practical need for dielectric materials arose out of the discovery of electricity, which in turn led to the invention of the light bulb, telegraph, telephone, and other electricity-oriented innovations. Electric line wires in service must be kept as dry as possible in order to function efficiently, and to cut down on loss of current. As electric technology developed, insulators were needed for telephone lines, electric power lines, and other applications. Also, as railroads began crossing the continent, there came the need for signal devices. Electricity had to be moved economically from one place to another to meet the...