Module 3: Defects, Diffusion and Conduction in Ceramics
Introduction
In this module, we will discuss about migration of the defects which happens via an atomistic process called as diffusion. Diffusivity of species in the materials is also related to their physical properties such as electrical conductivity and mobility via Nernst-Einestein relation which we shall derive. As we shall also see, the conductivity in ceramics is a sum of ionic and electronic conductivity and the ratio of two determines the applicability of ceramic materials for applications. Subsequently framework will be established for understanding the temperature dependence of conductivity via a simple atomistic model leading to the same conclusions as predicted by the diffusivity model. Subsequently we will look into the conduction in glasses and look at some examples of fast ion conductors, material of importance for a variety of applications. Presence of charged defects in ceramics also means the existence of electrical potential gradients, in addition to the chemical gradient, which results in a unified equation for electrochemical potential. Finally, we will look at a few important applications for conducting ceramic materials.
