Ceramic insulators are widely used in the electrical power transmission system. They possess a number of valuable properties: high mechanical and electrical strength, good chemical resistance etc. As these are clay products, their properties are related to the structural modification of clay when they are fired. The properties of these types of materials are determined to a considerable extent by the mullite content, the amount and the properties of the feldspar glass, and also the volume of sealed pores. Local ceramic industry was faced yield losses as the rejection rate was very high for the production of ceramic insulator. The research work was carried on ceramic body to improve the quality of these materials. The target audience of this book is the postgraduate students and the researchers who would like to understand the structural property relationship of ceramic insulator.