Physicochemical properties of ZnCl 2–NaCl–KCl eutectic melt

Abstract

Physicochemical properties of ZnCl 2–NaCl–KCl eutectic melt were studied at 200–300 °C for the first time. Firstly, it was reconfirmed that the eutectic composition is ZnCl 2:NaCl:KCl = 0.6:0.2:0.2 in mole fraction, and that the eutectic temperature is 203 °C. Then, the density, viscosity, and ionic conductivity of the ZnCl 2–NaCl–KCl eutectic melt were measured at 200–300 °C. At 250 °C, the density was 2.43 g cm −3, the viscosity was 42.0 cP and the ionic conductivity was 8.53 S m −1. The temperature dependencies of density and ionic conductivity were well fitted by the VTF equations with the same ideal glass transition temperature of 283 K (10 °C). It was found that the melt obeys the fractional Walden's rule which is explained by the decoupling effect. The electrochemical window of the melt was determined to be 1.7 V at 250 °C with the cathode limit being zinc metal deposition and the anode limit being chlorine gas evolution.