Disordering phenomena in superionic conductors

Superionic conductors are materials which exhibit exceptionally high ionic conductivity whilst in the solid state. The manner in which certain structures accommodate superionic conduction has preoccupied many scientists throughout the latter part of the last century, beginning with the early debate about the disordered structure of the superionic α-phase of silver iodide. In this review, the key methods that have been used to deduce structural disorder in superionic conductors are described, and the important results summarized. The review focuses on simple archetypal systems, since these have dominated the literature, concentrating on more recent work and including emerging methodologies for deducing structural disorder. In most cases, the interpretation of diffuse scattering, as observed in scattering measurements, has played a crucial role in the understanding of these highly disordered systems and this is considered in some detail.