Radiation Effects in Ceramics

Abstract

Ceramics are inorganic, nonmetallic materials, a class that includes solids with both crystalline and glassy (i.e., aperiodic) atomic structures. This article will emphasize radiation effects in conventional refractory oxide ceramics and glasses that display high-temperature strength, chemical inertness, and high electrical resistivity. The introduction to this issue cites various radiation environments to which materials may be exposed; a number of these environments receive mention in this article. However emphasis here is on giving the reader an overview of damage mechanisms and of the changes in key physical properties (optical, thermal, electrical, and mechanical) that can affect the behavior of these materials. The broad subject of radiation-damage phenomena in ceramics has recently been reviewed by Hobbs et al.Even at low doses of energetic radiation, whether particulate or electromagnetic, isolated atomic-level defects may be generated and can offer the potential to induce changes in physical properties. However for some applications such as fission reactors, fusion reactors (now in the conceptual design stages), and high-energy accelerators, one must deal with high fluences capable of generating relatively large damage aggregates such as dislocation loops and voids. Thus one must understand the evolution of damage microstructures from point defects to aggregates in both model materials and engineering ceramics. Even when induced changes are only electronic in nature, the effects on some properties (e.g., electrical conductivity) can be dramatic. In the following sections, evolution of the damage state and consequent changes in key properties are described, with some attention to the often critical role of impurities.