Stabilization of ferroelectricity in KNO3 embedded into MCM-41 molecular sieves

Measurements of the linear permittivity and third-order harmonic generation were carried out for KNO3 loaded molecular sieves MCM-41 with pores of 37 and 26 Å in comparison with bulk potassium nitrate. The samples were warmed up to 423 and 463 K from room temperature. The ferroelectric phase III was shown to occur upon cooling in both nanocomposites after warming till 463 K when it emerges also in bulk KNO3. Nanoconfinement led to the pronounced broadening of the temperature range of ferroelectricity. While under the thermal conditions when phase III does not arise in bulk KNO3, ferroelectricity was found only within pores of 26 Å.