This book presents research in the study of piezoelectric materials and devices. The developed concepts and ideas, as well as the presented theoretical, model and experimental results have been obtained by several internationally recognized research teams. The covered themes include the methods of determining the piezoelectric characteristics of non-uniformly polarized electroelastic solids, by using non-classical boundary integral equations; the mathematical modeling of polarization for polycrystalline ferroelectric materials, in strong electric and mechanical fields and the novel preparation technique to obtain lead-free piezoceramic materials with very high useful properties.