Materials in general consist of defects which can be divided into a variety of categories such as point defects or 0-D defects, line defects or 1-D defects and 2-D or surface defects. These defects play an important role in determining the properties of ceramic materials and in this context, the role of point defects is extremely important. In this module, we will learn about various point defects, the role of stoichiometry i.e. cation and anion excess and deficit, the role of foreign atoms on the defect chemistry. Subsequently, we will adopt a simple thermodynamic basis for calculating their concentration in equilibrium and then will extend the Gibbs-Duhem relation for chemical systems to the defects in ceramics considering them to be equivalent to the dilute solutions, an approximation which is fairly valid. This will lead us to the determination of defect concentrations as a function of partial pressure of oxygen which is an important exercise to establish the defect concentration vs pO2 diagrams, called Brower’s diagrams.
Nonstoichiometry, Diffusion and Electrical Conductivity in Binary Metal Oxides (Science & Technology of Materials), P.K. Kofstad, John Wiley and Sons Inc.
Physical Ceramics: Principles for Ceramic Science and Engineering, Y.-M. Chiang, D. P. Birnie, and W. D. Kingery, Wiley-VCH
Introduction to the Thermodynamics of Materials, David R. Gaskell, Taylor and Francis.
