Experimental investigations of the thermochemical properties of the ph
ases in the system Ba-Cu-O by means of DTA and calorimetric measuremen
ts are reported. The results together with critically selected data fr
om the literature are used for an assessment of the Gibbs energies of
the ternary phases (based on the Standard Element Reference State, SER
). For the binary subsystems critically assessed data from the literat
ure are used.