ABSTRACT
The understanding of chemical or ceramic one-component systems is based on isothermal and isobaric analyses or consideration of the simultaneous effect of temperature and pressure. The temperature and magnitude of the volume changes which occur during solid state polymorphic transitions and the aggregate and axial thermal expansion of each polymorph is extremely important to the use of ceramic materials. The greater specific volume of the crystal would cause an increase in the pressure of the system and the equilibrium between solid and liquid would thus shift to a position of higher pressure and lower temperature. In a qualitative way, one can predict the effect of changes on the equilibrium of a system by means of the principle of Le Chatelier. A metastable phase is fundamentally in a non-equilibrium state. However, it is frequently described as a state of "metastable-equilibrium" due to the extremely long time which is required to return to the stable equilibrium condition.
