This monograph provides researchers, engineers, postgraduates and lecturers working in the field of ferroelectric or piezoelectric and related materials with features of the structure-property relationships in modern piezo-active composites. These are piezoelectric composites which are active dielectric materials, which can be poled ferroelectric ceramics or domain-engineered single crystals poled along specific crystallographic directions. Current knowledge of the effective physical properties of these materials is lacking especially due to gaps of information in physical, chemical,...