Thermoelectric Powers in Palladium-Silver and Palladium-Rhodium Alloys

Thermoelectric powers have been measured in the temperature range 77°K to 273°K in the alloys of palladium with silver. The absolute thermoelectric power is found to be highly sensitive to the presence of unoccupied $d$-band states, and a marked variation with composition is also found in alloys with more than 90% of either element. This latter behavior is ascribed to a departure of the Fermi surface from an accurately spherical form as the $s$-electron concentration increases above 0.9 per atom in the silver-rich alloys, and to a contribution to conduction from $d$-band holes in the palladium-rich alloys. The values of thermoelectric power obtained for the pure metals by extrapolation from the results for alloys where these effects are absent are in good agreement with estimates made on the basis of simple theoretical models. Results of measurements on some palladium-rich palladium-rhodium alloys are also presented and discussed briefly.