NONSTOICHIOMETRIC ZINC-OXIDE AND INDIUM-DOPED ZINC-OXIDE - ELECTRICAL-CONDUCTIVITY AND IN-111-TDPAC STUDIES

Indium-doped zinc oxide powders have been prepared which show room-tem perature electrical conductivities as high as 30 Omega(-1) cm(-1). The indium doping apparently occurs as Zn1-xInxO, Zn1-yInyO1+y/2, or a co mbination of these. Optimum conductivity occurs for Zn1-xInxO where th e maximum value of x obtained was about 0.5 at%. This substitution res ults in a lattice volume expansion of 0.4%. The degrees of sample redu ction were determined by iodimetric titration. Time differential pertu rbed angular correlation (TDPAC) spectroscopy on indium doped zinc oxi de is consistent with indium substituting at normal zinc sites in the ZnO lattice. TDPAC studies on zinc oxide annealed under zinc vapors sh ow a second environment for the In-111 probe. In this case, there is a n unusually high temperature dependence of the electric field gradient which may be caused by a nearby zinc interstitial. An important concl usion of this work is that zinc interstitials are not ionized and do n ot therefore contribute significantly to the increased conductivity of reduced zinc oxide. (C) 1996 Academic Press, Inc.