The aim of this book is to understand the different dielectric relaxation processes and electro-optical characteristics in the materials containing antiferroelectric and ferroelectric phases and investigation of twist grain boundary (TGB) phases in the binary mixtures of cholesteryl caprylate (ChC) and nonyloxybenzoic acid (NOBA). This book contains four chapters. Chapter 1 describes a brief overview on liquid crystals. Relaxation phenomena occurring in ferroelectric and antiferroelectric liquid crystals have been discussed. Chapter 2 describes the experimental techniques for thermodynamical, optical electrical measurements. In Chapter 3, dielectric, switching and electro-optic studies of multicomponent antiferroelectric liquid crystal mixture (W-312A), and a single component antiferroelectric liquid crystal MOPB(H)PBC, have been given. In Chapter 4, phase diagram of 21 mixtures mixture of cholesteryl caprylate (ChC) and nonyloxybenzoic acid (NOBA)) has been drawn with the help of electrical, optical and thermodynamical studies.