The thermodynamic properties were determined, by means of thermogravimetry, between 250 and 450C. The O pressures ranged from 10-5 to 1atm, under conditions of thermodynamic equilibrium. The O non-stoichiometry was made up of 2 parts: with one part being a fully extractable quantity and the other being a residual quantity. The reversible deviation from stoichiometry could be treated in terms of the interstitial O content. The oxidation process could be written such that O2- occupied a (½½0) site while h0 was an electronic hole. The point-defect model seemed to be correct, and the formation of 2 holes for 1 intercalated O was assumed. The first energy of formation of interstitial O was equal to 0.45eV, at between 450 and 325C, with a second (5.9eV) between 325 and 350C. This large value was attributed to the difficulty which was encountered in oxidizing the material.

Thermodynamic Properties, Non-Stoichiometry and Point Defects of HgBa2Ca2Cu3O8. V.Guillen-Viallet, J.F.Marucco, D.Colson: Superconductor Science and Technology, 2000, 13[8], 1162-6