Synthesis, Characterization, Fast Ion Transport and Phase Transition In a [Ag2HgI4:0.x AgI] Type Superionic Mixed Composite Materials (x = 0.2, 0.4, 0.6 mol. wt. %)

Experimental investigations concerning the preparation and characterisation of the system [Ag2HgI4:0.x AgI] (x=0.2, 0.4, 0.6 mol. wt. %),, have been undertaken with a view to evaluate the transport properties of the mixed system and to identify the fast ion conducting compositions. Powder samples of various compositions containing 0.2, 0.4 and 0.6 mol. wt. % [Ag2HgI4:0.x AgI] (x=0.2, 0.4, 0.6 mol. wt. %), were synthesized by solid state reaction. Samples were analyzed using powder X-ray diffraction (XRD), differential thermal analysis (DTA) and thermo-gravimetric analysis techniques in order to determine their crystal structure and phase transition temperatures. These studies have revealed the formation of new substances having phase transition temperatures similar to that of AgI. Detailed electrical conductivity measurements carried out in the frequency range 100 Hz- 10 kHz and over the temperature range 90°-170 °C by a Gen Rad 1659 RLC Digibridge have identified the best conducting composition namely 4 mol. wt.% [Ag2HgI4:AgI], exhibiting an electrical conductivity of 1.14×10-1 S cm-2 K at 393 K and an activation energy of 1.6 eV for Ag+ ion migration within the solid. The occurrence of fast ion transport due to silver ion migration in several compositions of the above mixed system has been explained on the basis of “hard and soft acids and bases” principle and ion exchange chemistry.