PHASE-DIAGRAMS UNDER HIGH TOTAL GAS-PRESSURES ELLINGHAM DIAGRAMS FOR HOT ISOSTATIC PRESS PROCESSES

Ellingham diagrams are very powerful phase diagrams to evaluate equilibrium phases obtained by chemical reactions. These phase diagrams were extended to higher pressures to examine stable phases under high total gas pressures. The variables under consideration consist not only of temperature and partial pressure of a gas involving the chemical reactions, but also total gas pressures. These new phase diagrams are applied to predict stable phases under hot isostatic pressing conditions (HIP phase diagram). Examples of silicon nitride sintering, and aluminium nitride sintering were given as the case of low oxygen partial pressure HIP phase diagrams. Bismuth based superconducting ceramics are discussed as an example for a high partial oxygen partial pressure HIP phase diagram. In all cases the proposed HIP phase diagrams agree well with experimental observations. © 1990.