Suppression of Vaporization in Copper--Silver-Selenide Thermoelectric Materials

摘要

Current thermoelectric generator designs using P-type (Cu,Ag) sub 2 Se specify hot cap temperatures of 850 to 1000 exp 0 C for target generator efficiencies. Vapor pressures of volatile species above this material are high even at 850 exp 0 C. Thus the only way these designs can be made feasible is to develop a vapor suppression system which will inhibit (Cu,Ag) sub 2 Se degradation and weight loss. Suppression of vaporization in P-type copper--silver-selenide (Cu,Ag) sub 2 Se, was attempted by applying coatings and by mechanical barriers. The difficulties encountered with this material are associated with its very high thermal expansion and change in stoichiometry. Coatings which were both chemically inert and reactive with selenium were examined and include both crystalline and glassy coatings. Vaporization rates for inert and glassy coatings were exp 1 / sub 5 the rates of uncoated control samples. Reactive coatings reduced 850 exp 0 C isothermal weight loss rates to exp 1 / sub 10 that of uncoated controls. Theoretical and experimental studies have been preformed on bonded elements containing both glass sleeves and coatings. Results obtained with this concept have shown the greatest promise for minimizing 900 exp 0 C vaporization degradation. (ERA citation 03:055330)