Phase equilibria in the titanium-oxygen system

Data in the literature on the Magneli oxides of titanium have been critically evaluated and equations have been developed from these data for the standard-state Gibbs energy of formation of the following oxides: Ti4O7, Ti5O9, Ti6O11, Ti8O15, and Ti9O17. Examination of those data yielded the following: Delta G(f) degrees(TiO7/4) = -845.26 + 0.1490 . T kJ/mol, 1150 K < T < 1304 K Delta G(f) degrees(TiO9/5) = -867.04 + 0.1564 . T kJ/mol, 1150 K < T < 1373 K Delta G(f) degrees(TiO11/6) = -879.58 + 0.1600 . T kJ/mol, 1150 K < T < 1304 K Delta G(f) degrees(TiO15/8) = -894.79 + 0.1642 . T kJ/mol, 1150 K < T < 1304 K Delta G(f) degrees(TiO17/9) = -900.36 + 0.1660 . T kJ/mol, 1150 K < T < 1304 K Similar equations for Ti16O31 and Ti50O99 have been estimated from their respective data at 1304 K. The result of that analysis has lead to the following equations: Delta G(f) degrees(TiO31/16) = -916.93 + 0.1703 . T kJ/mol, T approximate to 1304 K Delta G(f) degrees(TiO99/50) = -935.63 + 0.1776 . T kJ/mol approximate to 1304 K These equations, along with data in the literature, have been used to construct the Ti-O stability diagram.