USE OF THE RIGID BAND FORMALISM TO INTERPRET THE RELATIONSHIP BETWEENO CHEMICAL-POTENTIAL AND ELECTRON-CONCENTRATION IN LA1-XSRXCOO3-DELTA

The equilibrium oxygen chemical potential of mixed oxygen ion and elec tron conducting perovskites La1-xSrxCoO3-delta, was measured as a func tion of delta and x by high temperature oxygen coulometric titration. An almost linear decrease in the chemical potential is observed with i ncreasing net electron concentration. The observed behavior is interpr eted to reflect the corresponding change in the Fermi level upon gradu ally filling up states in abroad electron band with electrons induced by vacancy formation and Sr doping. Assuming a rigid band formalism, a n apparent density of states at the Fermi level was calculated, the va lue of which is in good agreement with that obtained from XPS.