**1. Introduction**

The result of scientific progresses in materials science and the continuing developments of modern industry, have given rise to the continual demand for advanced materials that can satisfy the necessary advanced properties and qualities. This requirement for advanced materials with specific properties brought about the gradual transformation of materials from their basic states(monolithic) to composites. Recent advances in engineering and the process‐ ing of materials have led to a new class of materials called Functionally Graded Materials (FGMs). These represent a second generation of composite materials and have been designed to achieve superior levels of performance.

FGMs are a type of composite material and are classified by their graded structure. Specifically, an FGM typically consists of a composite material with a spatially varying property and is designed to optimize performance through the distribution of that property. It could be a gradual change in chemical properties, structure, grain size, texturization level, density and other physical properties from layer to layer. FGMs have a graded interface rather than a sharp interface between the two dissimilar materials. Using a material with, for example, a graded chemical composition, minimizes the differences in that property from one material to another. No obvious change may take place in their chemical composition if the gradient is smooth enough, and if the transition is smooth, the mismatches in the property from one point in the material to another will be limited. Therefore, the ideal FGM has no sharp interfaces. Moreover, there will be no single location that is inherently weaker than the rest of the composite.

The aim of the production of FGMs is the elimination of the macroscopic boundary in materials in which the material's mechanical, physical and chemical properties change continuously and have no discontinuities within the material. Thus, these materials exhibit superior mechanical properties when compared to basic (monolithic) and composite materials.

In the past, the composition of FGMs typically included at least one metal phase. Recently, great attention has been devoted to ceramic-ceramic and glass-ceramic systems due to their attractive properties. Ceramic materials are designed to withstand a variety of severe in-service conditions, including high temperatures, corrosive liquids and gases, abrasion, and mechan‐ ical and thermal induced stresses. In this chapter, special attention will be given to the new advances in Functionally Graded Ceramics (FGCs), their processing and applications.
