Some solid-solid phase transitions yield a structure accompanied by a high conductivity, viz. fast-ion conduction. Our efforts are focused on 'locking-in' or preserving the high conductivity structure by the incorporation of appropriate guest ions. Differential scanning calorimetry (DSC) is used to quantitatively monitor the progress of this structure stabilization or guest-host interaction effects. The DSC data are used to calculate fundamental thermodynamic quantities, viz. heat of transition, heat of complex association, partial molar heat of solution/substitution at infinite dilution chi, the change in heat content/enthalpy of the host lattice Delta H-s(o) and the 'recovered lattice energy', Delta H-L(o).