EXCHANGE OF NA+ WITH CD2+ IN POLYCRYSTALLINE BETA''-ALUMINA IN MOLTEN-SALTS

The thermodynamics and kinetics of the exchange of Na** plus with Cd**2** plus in polycrystalline beta double prime -alumina in NaCl-CdCl//2 melts are studied. It is found that the Cd**2** plus ions favor the melt. At degrees of exchange between 10 and 40% a yellow-brown coloration of the samples is observed. The grain boundaries do not influence noticeably the equilibrium but considerably hinder the ion-exchange process. The kinetic study shows that the rate of the ion-exchange process is controlled by the diffusion of the ions through the exchanged layer. The ionic conductivity of the Na** plus -Cd**2** plus - beta double prime -alumina samples is measured. Its activation energy coincides quite well with that of the ion-exchange process.