New facets for the role of defects in ceramics

D have a public relations problem—for too long, they have been regarded as the “bad guys.” Defects generally have been dismissed as deleterious to properties and performance of ceramic materials and devices, and, in turn, considerable efforts have attempted to either minimize their concentration or to counterbalance their detrimental impact. We know, however, that defects can generate value. For example, defects and impurities cause highly desirable color in gem-quality diamonds (see sidebar). Today, advances in synthesis, characterization, and theoretical modeling of ceramics are beginning to challenge the “bad guy” reputation of defects. The intentional and purposeful introduction of defects, with control over type, concentration, and location, presents an opportunity to make use of “good guy” defects. In this new role, defects are a tool for tuning and enhancing properties and even enabling new functionalities. This perspective focuses on current work and future potential for this role redefinition by highlighting advances in methodologies and scientific examples where defects have been embraced and applied to improve material function.