The hydrogen bond in ferroelectricity and the role of high pressure research

Abstract

The hydrogen bond plays an all important role in determining the physical properties of a variety of classes of ferroelectrics and antiferroelectrics of which potassium dihydrogen phosphate (KDP), lithium trihydrogen selenite and Rochelle salt are examples. This role is evidenced by the usually large isotope effects on the static and dynamic properties of these materials observed on deuteration. It has been demonstrated that high pressure is an extremely useful (sometimes essential) variable in elucidating these properties. Results on both deuterated and nondeuterated crystals will be summarized and discussed illustrating the usefulness and/or uniqueness of pressure as a variable in such studies. Emphasis will be on the KDP-class of crystals as this is the class which has been most widely studied and understood.