Standard Article

Defects in Solids

  1. Richard J. D. Tilley

Published Online: 15 DEC 2011

DOI: 10.1002/9781119951438.eibc0058

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Tilley, R. J. D. 2011. Defects in Solids. Encyclopedia of Inorganic and Bioinorganic Chemistry. .

Author Information

  1. University of Cardiff, Cardiff, UK

Publication History

  1. Published Online: 15 DEC 2011

Abstract

The chemical aspects of defects of relevance to inorganic crystalline solids are described, especially the close links with the composition of crystalline nonmetallic inorganic nonstoichiometric compounds. The discussion begins with a description of simple point defects in stoichiometric materials and the relationship between the population of these defects and the Gibbs energy of formation of the defects. This includes defects in monatomic structures and balanced populations of point defects, Frenkel and Schottky defects, in binary compounds. Superionic compounds that contain quasi-liquid cation arrays are considered as extreme cases of these simpler defect populations. Nonstoichiometric compounds treated from the standpoint of small populations of point defect populations are considered, including color centers. Defect chemistry, the incorporation of point defects into chemical nomenclature, is described, including the Kroger–Vink notation and the construction of Brouwer diagrams. Grossly nonstoichiometric compounds, including those that can be considered to contain point defects or structurally organised defect clusters, such as the iron oxide wüstite, and the defect fluorite structures are illustrated. Extended defects portray a wider view of defect chemistry, in which planar faults and intergrowths are prominent structural features of many complex inorganic solids. To illustrate planar defects, examples are taken from crystallographic shear phases, twinned structures, intergrowth structures, and the niobium oxide block structures. Structures containing pentagonal columns linked by vertices provide an example of structures that contain columnar defects. Examples of inorganic solids that possess more than one defect type are taken from layered perovskite phases, tungsten bronzes, and high-temperature ceramic superconductors. The final section is concerned with structures that were once described as containing defects but that have recently been found to be essentially defect free. These materials, in which defects are eliminated by the device of continuous structural modulation affecting one part of the structure, are widespread over many classes of inorganic solids. Examples drawn from oxides related to tantalum pentoxide, layer misfit phases, and anion-excess fluorite-related materials.

Keywords:

  • point defect;
  • extended defect;
  • nonstoichiometric compound;
  • defect formation energy;
  • Brower diagram;
  • defect clusters;
  • anion-excess phase;
  • anion-deficit phase;
  • crystallographic shear structure;
  • block structure;
  • modulated structure;
  • incommensurate structure;
  • layer misfit structure