Ion conduction in the Ag2HgI4-Cu2HgI4 systems doped with Cd2+, K+, and Na+

Ion conductivities of face centered cubic Ag2HgI4-Cu2HgI4 systems doped with Cd2+, K+, and Na+ were measured. In 67 mol% Ag2HgI4 solid solution doped with Cd2+ ions, the phase transition occurs at a lower temperature than in the parent compounds and the system shows higher conductivity. The increase in conductivity is discussed in terms of vacancies produced. K+ doped Ag2HgI4 exhibits higher conductivity prior to the phase transition, which is attributed to lattice loosening. A decrease in conductivity is observed above 140 degrees C. This is interpreted in terms of anion framework collapse. Na+ doped Ag2HgI4 shows high conductivity for the high temperature phase because of the small size of Na+ ions. The activation energy for ionic motion for all the samples is calculated from the graph of log(sigma T) versus 1/T. (C) 1996 Academic Press, Inc.