Seebeck Effect in (U,Pu)Osub(2+-Y) and Its Influence on Oxygen Migration

摘要

Thermoelectric potentials have been investigated in hypo- and hyperstoichiometric uranium-plutonium mixed oxide pellets up to temperatures of 1800 K. At low temperatures, below 1200 K the Seebeck coefficient is positive. It vanishes at temperatures between 1200 K and 1800 K and changes its sign with increasing temperatures. This behavior is explained by a change of the conductivity mechanism from p- to n-type. The absolute value of the Seebeck coefficient depends strongly on the O/M-ratio. It is big for the stoichiometric region and small for higher deviations from stoichiometry. Thermoelectric power provides one of the forces which drive ions along the temperature gradients. Another force originates in the differences of the lattice forces of the various ions, atoms, and vacancies. Both forces can be described by the heat of transport of oxygen ions which contains a thermoelectric and a thermic part. The parts are calculated using the known values of the overall heat of transport and that of the measured Seebeck coefficient. (Atomindex citation 10:459782)