Model Calculations of the Micrometer to Millimeter Intrinsic Absorption for Simple Ceramics

Authors

John R. Hardy, University of Nebraska - LincolnFollow
P. J. Edwardson, University of Nebraska - Lincoln
J. A. O'Gara, University of Nebraska - Lincoln

Date of this Version

11-15-1984

Comments

Published in Physical Review B Volume 30, Number 10, 15 November 1984. Copyright © 1984 The American Physical Society. Used by permission.

Abstract

A systematic study has been made of the strength of the intrinsic absorption, or loss, for millimeter to micrometer electromagnetic radiation propagating in simple ceramic materials. This study employed a number of model diatomic systems whose simplicity enabled the basic two-phonon decay process, responsible for this intrinsic loss, to be computed with precision, even at the lowest frequencies, on a dedicated microcomputer. It was found that, at least at low frequencies, the loss was a relatively structureless universal function of the atomic mass ratio, in general agreement with earlier results for real alkali halides. In particular, it was found that, if one atomic mass was markedly increased, the low-frequency damping dropped dramatically and a "window" appeared in the loss function. This behavior and its origins are discussed and illustrated by predictions of the absolute values of the intrinsic low-frequency losses for MgO and SrO at room temperature. The values for MgO are almost an order of magnitude larger, and in reasonable accord with values measured for typical ceramics, when estimated extrinsic losses are subtracted. The present studies also provide a natural explanation of the general observation that the loss at the fundamental lattice resonance frequency is, at least in centrosymmetric systems, dominated by three-phonon decay.