A free volume model for transport in fused salts has been tested by electrical conductance measurements on Ca(NO3)2 + KNO3 melts. Low temperature results exhibit rapidly changing activation energies and fit precisely an equation of the predicted form Λ = AT-1/2 exp(-k/(T - T0)). The constant T0 agrees with the measured glass transition temperature and represents the temperature for zero free volume in the liquid. T0 is shown to have a characteristic value for all molten salts, which depends on the electrostatic field strength of the constituent ions. Changes of T0 with composition are the main source of the composition dependence of conductance in the present system. Experimental values of k for molten salts indicate a predisposition of holes in the liquid to be of ionic size. The model offers an explanation of the glass-forming ability of molten ZnCl2.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry