**Abstract**

Ferroelectric ceramic is one of the most important functional materials, which has great importance in modern technologies. A ferroelectric ceramic simultaneously exhibits dielectric, piezoelectric, ferroelectric, and pyroelectric properties. The inherent ferroelectric properties are directly related to long-range electric dipoles arrangement in the ferroelectric domains and its response to external stimuli. However, the interruption of the long-range ordering of dipoles leads to the formation of a special class of material is known as relaxor ferroelectric. It shows quite different physical properties as compared to ferroelectric (normal ferroelectric). The origin and design of relaxor ferroelectric are quite interesting for fundamental perspective along with device applications. Therefore, the origin of relaxor ferroelectric along with its fundamental understanding for possible future applications, have been explained briefly in the present chapter.

**Keywords:** relaxor ferroelectric, spontaneous polarization, ferroelectric domains, polar nanoregions, diffuses phase transition, solid solution
