The book is arranged in six chapters. The first chapter gives a general introduction and a brief review of ferroelectrics especially the perovskite and layered perovskite ferroelectric ceramics. The second chapter describes the dielectric diffuseness and impedance spectroscopy study of CuNb2O6 incorporated BaTiO3. Chapter three elaborates the influence of Ba2+ substitution by Bi3+ on dielectric, impedance and conductivity behavior of BaBi2Nb2O9. Fourth chapter presents the detail of the influence of substitution on dielectric and impedance spectroscopy of Sr1-xBi2+yNb2O9. Studies of structural and electrical properties of Ca1-xBi2+yNb2O9 have been described in the fifth chapter. Each chapter from second to fifth describes the details of the synthesis by chemical route, materials characterization and electrical characterization. Materials characterizations include the studies of TG-DTA, XRD, TEM, SEM, EDAX analysis, relative density etc; while the electrical characterizations study the dielectric constant, loss tangent, impedance, ac and dc conductivity, and modulus etc. The last chapter i.e., sixth chapter summarizes the important data obtained from second to fifth chapter.