This text summarizes recent developments in silicon nitride ceramics with respect to processing, mechanical properties and potential applications. It presents opportunities of controlling the microstructural development and gives an analysis of the enormous progress in improving room temperature strength. Special emphasis is given to the influence of the grain boundary phase on the high temperature properties. The articles describe the scientific advances in understanding creep deformation, subcritical crack growth and fatigue behaviour. The discussion of the stability of the amorphous grain boundary and devitrification behaviour demonstrates the possibilities and limits for the development of high temperature resistant materials. All authors are leading experts in this field and this book has been arranged to achieve a textbook format which will be of value to researchers already active in the field as well as newcomers and students.