Phonon Spectroscopy of Solid Dielectrics

Abstract

A method for studying solid dielectrics under conditions of nonstationary propagation of subterahertz phonons is presented. The method analyzes the transport characteristics of thermal phonons in the helium (He) temperature range (2–4 K) in diffusion mode and makes it possible to investigate the following: the kinetic characteristics of thermal phonons in single crystals of solid solutions; the contribution to phonon scattering from the concentration, type, and positions of a substitutional impurity, defects comparable with the wavelength (clusters, phase inhomogeneities, dislocations), low-energy excitations of various nature, including those associated with the formation of an equilibrium configuration of vacancies in the anionic sublattice with respect to substitutional impurity cations; equilibrium criteria in the system of nonequilibrium phonons–low-energy excitations; peculiarities of the phonon spectrum of nanostructured materials; the relationship between the diffusion coefficient of subterahertz phonons and the system of grain boundaries (GB), grain size, conditions for the formation of a “gap” in the phonon spectrum of nanostructured ceramics; spectral properties of GB, their relationship with the technological conditions of synthesis, to evaluate the average thickness and acoustic impedance of GB for a sample; the features of thermal phonon transport in amorphous dielectrics (glasses and glasslike materials) near the thermal conductivity “plateau,” the possibility of “gap” formation in the spectrum of phonon states; subterahertz phonon transport in ceramics based on ferroelectrics, electrolyte solid solutions, and cermets.