Piezoelectricity is the ability of certain crystalline materials to develop an electric charge proportional to a mechanical stress. Since its discovery, the piezoelectricity effect has found many useful applications, such as the production and detection of sound, generation of high voltages and frequency, microbalances, and ultra fine focusing of optical assemblies. It is also the basis of a number of scientific instrumental techniques and everyday uses such as acting as the ignition source for cigarette lighters and push-start propane barbecues. This book gives a review of the state of art in polycrystalline piezoelectric ceramic materials, which covers the processing, properties, characterisation and applications of piezoelectric ceramic materials.