A crystallo-chemical approach to superionics

An attempt has been made to integrate concepts in structure, bonding and superionic conductivity so that one can distinguish intuitively between an ionic conductor and a superionic conductor and possibly make predictions about conductivity in a hypothetical compound. The physical origin of electronegativity and break-up of a heteropolar bond into covalent and ionic fractions are stressed as being relevant and prominent pieces in the jigsaw puzzle of understanding the phenomenon of superionic conductivity. Glass formation and defects in glass also enter into the larger context of disordered superionic conductors. The hard-soft acid-base principle completes the picture by providing an important empirical basis for understanding solid-state ionic materials. The high ionic conductivity of alpha-AgI and alpha-Li2SO4 is explained by using the above ideas. (C) 1997 Elsevier Science Ltd. All rights reserved.