In this important book, the author summarizes and generalizes the results of 25 years of work in this exciting field, which has been developing extensively within the last few decades. The reader will find discussions of many crystals that were investigated in the microwave region, including low-dimensional and ferroelectric semiconductors, protonic conductors, quasi-one-dimensional H-bonded. and other order-disorder ferroelectrics. This volume is an essential reference for all scientists and graduate students whose interests are connected to the physics of ferroelectrics and related materials; the physics of structural phase transitions; and superionic conductors. It will also be of value to those interested in developing or exploiting microwave measurement techniques.