Potassium and Sodium Filled Skutterudites

Abstract

Interstitial voids of the cubic CoSb 3 type skutterudite structure can be filled with sodium and/or potassium atoms. Such filled skutterudites have the general formulas, K y Co 4 Sb 12 and Na y Co 4 Sb 12 , where y indicates the filling fraction of potassium and sodium, respectively, in the CoSb 3 cubic crystal structure, and has a value greater than zero and less than one. Also sodium-filled and/or potassium-filled skutterudites of the general formula, (K, Na) y T 4 Pn 12 are made, where T denotes Fe, Ru, Os, Co, Rh, or Ir; and “Pn” denotes one of the pnicogen elements P, As, or Sb. Again, y has values less than one.

1 . Filled CoSb 3  type skutterudites in which interstitial voids in the cubic CoSb 3  structure contain only potassium or sodium atoms, and in which the filling fraction of potassium or sodium atoms is 0.2 to 0.6. 
     
     
         2 . A filled CoSb 3  type skutterudite as recited in  claim 1  having the formula K y Co 4 Sb 12 , where y has a value in the range of 0.5 to 0.6. 
     
     
         3 . A filled CoSb 3  type skutterudite as recited in  claim 2  having the formula K y Co 4 Sb 12 , where y has a value of 0.6. 
     
     
         4 . A filled CoSb 3  type skutterudite as recited in  claim 1  having the formula Na y Co 4 Sb 12 , where y has a value in the range of 0.5 to 0.6. 
     
     
         5 . A filled CoSb 3  type skutterudite as recited in  claim 4  having the formula Na y Co 4 Sb 12 , where y has a value of 0.6. 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . (canceled)