Infrared Spectra of Inorganic Dielectric Solids

Abstract

The lattice vibration spectrum of a solid has recently been characterized by one single frequency, which is defined as the frequency of the center of gravity of the spectrum, called “centro-frequency”. Here the experimental determination of this frequency is shown in detail for a number of solids the vibrational spectra of which became available recently. Emphasis is given to spectral data at various temperatures, from 4°K to about 1000°K, and at the various major crystallographic directions. The “centro-frequencies” at room temperature and higher temperatures show almost no change; whereas, at low temperature, the “centro-frequencies” consistently show a very definite increase. The result reveals a definite increase in binding energy with temperature decrease. A considerably higher resolution, particularly in the broad band areas, was obtained with spectra at very low temperatures.