Thermoelectric powers of cells with NaF-AlF3-Al2O3 melts

A thermodynamic description of the Peltier heat at the aluminum and the oxy gen electrode in the system NaF-AlF3-Al2O3 is given. The thermoelectric pow er in melts with molar ratios n(NaF)/In-AlF3 from 3.0 to 1.0, saturated wit h alumina are measured. Seebeck coefficients for molten fluoride electrolyt es saturated with alumina, electrolytes that are relevant for aluminum elec trowinning electrolysis cells, are reported. The results allow determinatio ns of Peltier heats of aluminum, oxygen and carbon electrodes in NaF-AlF3 e lectrolytes saturated with alumina. For molar ratios of n(NaF)/n(AlF3) betw een 2.6 and 1.2, there is a Peltier heating of the aluminum cathode. This h eating is in the same order of magnitude as the electrolyte Joule heat, whe n the current density is 0.7 A cm(-2). For molar ratio n(NaF)/n(AlF3) equal to 1.0 the Peltier effect at the aluminum electrode approaches zero. From theoretical considerations we expect a drop also for molar ratio 3.0. For t he anode we report a Peltier cooling that is larger than the heat produced by the anodic overvoltage, in melts with NaF/AlF3 molar ratio between 2.6 a nd 1.2 saturated with alumina.