INCORPORATION OF MONOVALENT IONS IN ZNO AND THEIR INFLUENCE ON VARISTOR DEGRADATION

An atomistic simulation technique has been used to predict the spatial arrangement of the dopant species sodium, lithium, and chlorine withi n the zinc oxide lattice. The alkaline oxides are preferentially incor porated via a self-compensating mode, forming interstitial cations whi ch hinder the migration of zinc interstitials and hence slow the degra dation of the varistor. The addition of chloride ions is shown to nega te this effect by forming sodium and chloride substitutional defects r ather than any species involving sodium interstitial ions.