Synthesis and processing of AgInO2 delafossite compounds by cation exchange reactions

In recent years, ternary noble metal oxide compounds based on the delafossite structure have attracted great interest because of their potential use as transparent conductors. In this work, the experimental conditions which affect the synthesis and properties of Ag-based compounds by the cation exchange technique was explored. The reaction between AgNO3 and NaInO2 was performed at temperatures ranging from 200 to 300 degreesC in air over a period of 48 h or more. With X-ray diffraction, the phase distribution and crystallite size was monitored and related to the experimental conditions. Electron microscopy was also utilized to observe the phase distribution and locate the presence of secondary phases such as Ag metal. From these results, it was concluded that the volume change associated with the NaInO2 to AgInO2 transformation affected the delafossite crystallite size. The effects of KNO3 in promoting the cation exchange reaction were also discussed in terms of stabilizing the AgNO3:NaNO3:KNO3 solution. Finally, it was shown that n-type AgInO2 with a conductivity of 6 S cm(-1) was synthesized by modifying the precursor NaInO2 phase. (C) 2002 Elsevier Science B.V All rights reserved.