Ferroelectricity is the property of some materials that have an electric polarization which can be reversed by applying an external electric field. The materials that exhibit ferroelectricity are known as ferroelectric materials. All the ferroelectric materials are pyroelectric. The permittivity of ferroelectric materials is very high especially when close to the phase transition temperature. They are used to make capacitors with tunable capacitance. Ferroelectric capacitors are made up of a pair of electrodes sandwiching a layer of ferroelectric material. This book attempts to understand the multiple branches that fall under the discipline of ferroelectric materials and how such concepts have practical applications. It covers in detail some existent theories and innovative concepts revolving around ferroelectric materials. This book will prove to be immensely beneficial to students and researchers in this field.