Mats Hillert has shown [*] that what is called a Phase Diagram is derivable from a projection in a so-called Property Diagram. The (molar) Gibbs Energy as the property is plotted along the **z**-axis as a function of two other variables **x** and **y**. For binary systems, for example, T equals **y** and the mole fraction x equals **x**. It must be emphasized that the total pressure P must be kept constant for this representation.Â

Our partners at Ex-Mente have developed aÂ tool that allows to visualize the above 3D-interrelationship between the molar Gibbs Energies of the phases occurring in a binary system and the corresponding phase diagram. The visualization shows, in a perspective view, the three-dimensional Gibbs energy vs Temperature vs molar fraction (G-T-x) relationship in cartesian representation. In the respective Gm vs x diagrams, i.e. for given values of T and P, the equilibrium condition Gm=min for a given value of x is used to establish the one- or two-phase regions. On the **x**–**y**-plane, the phase diagram is depicted inÂ its usual Temperature vs molar fraction representation. By turning the mouse wheel, the temperature of the correspondingÂ G-x vertical graph is changed interactively.

Two interactive diagrams were generated, one for a metallic system and another one for a ceramic system:

- Pb-Sn interactive diagram
- Al
_{2}O_{3}-CaO interactive diagram

Concerning the Al_{2}O_{3}-CaO interactive diagram, it should be born in mind that all Gibbs Energies must be given for one mole of total component oxides. Thus the composition of the compound CaO.Al_{2}O_{3} corresponds to (CaO)_{0.5}(Al_{2}O_{3})_{0.5}. Also the Gibbs Energy of CaO.Al_{2}O_{3} has to be scaled down accordingly in order to be able to insert a correct data point in the Gm vs x diagram.

Please be aware that the behavior of the interactive diagram may be browser dependent.

[*] Mats Hillert, Phase Equilibria, Phase Diagrams and Phase Transformations – Their Thermodynamic Basis, Cambridge University Press,Â 2^{nd} edition (2008), p. 158.