Phase diagrams crystallinity and conductivity

The establishment of phase diagrams for polymer electrolyte systems where the stable regions of the various crystalline phases and the intercrystalline amorphous phase are defined, determining the relationship between these and their characterisation as a function of temperature and composition of the electrolyte, is therefore extremely useful, e.g. in predicting the ionic conduction behaviour of electrolytes. These phase diagram studies were initiated because ionic conductivity studies showed considerable variations as a function of several experimental parameters, such as thermal history.  

The relationship between the levels of conductivity obtained for a given electrolyte and, for example, the volume fraction of coexisting crystalline and amorphous phases, is not totally direct or simple. There are, simultaneously, many other factors involved, including nature, concentration and mobility of charge carriers. However, phase diagrams contribute descriptively, at a certain level, to a better understanding and explanation for the dependence of a particular property on salt concentration and temperature. Nevertheless, it is necessary to take certain issues into account  

Phase diagrams have been constructed based on information derived from different techniques, such as thermal analysis differential scanning calorimetry (DSC), differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction, NMR, optical microscopy and conductivity studies. 

As stated above, we must take into account that the possibly slow nature of ionic transport and crystallisation kinetics, especially at low temperatures, may mean that the system is far from equilibrium. In most cases, hystereses observed in measurements of the physical properties of polymer electrolytes occur because equilibrium phases have not yet been established. 

As for the PEO -ZnCl2 system, Yang and Farrington found (by DSC analysis) an intermediate complex for n 4 compositions, melting in the 

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