The temperature dependences of the linear dielectric permittivity, the third harmonic amplitude, and the heat capacity of nanoporous silica matrices MCM 41 with cellular channels (3.7 and 2.6 nm in diam eter) filled with KNO 3 have been investigated in comparison with those obtained for bulk potassium nitrate. Measurements have been performed during heating and cooling in the range from room temperature to 463 K. Anomalies corresponding to structural phase transitions have been observed. A significant broadening of the temperature region of the existence of the ferroelectric phase III of potassium nitrate upon cooling has been revealed. This broadening increases with a decrease in the size of pores. It has been shown that, in the nanocomposites with potassium nitrate, the ferroelectric phase can also be formed during heating. The effi ciency of observation of the third harmonic generation for studying nanocomposites with the ferroelectric phase has been demonstrated.

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