Phase transition of the potassium nitrate ferroelectric in a nanoporous matrix

Nanocomposite materials which are silicate nanoporous matrices filled with KNO$_3$ are studied by the calorimetric method. The anomalies observed in the specific heat related to the ferroelectric phase transitions are studied in the framework of the smeared phase transition theory. The extrapolation of results confirms the assumption made before that there is the minimum pore size in the nanocomposite at which KNO$_3$ at room temperature will be completely in the ferroelectric state.