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Heat capacity, thermal dilatation, sensitivity to pressure and permittivity of NH 4 HSO 4 embedded into glass matrices with a pore size of 320 nm and 46 nm were studied. Large difference in the thermal expansion of both glass and ferroelectric leads to a "clamped" state of NH 4 HSO 4 in nanocomposites and to the phase transition temperatures change. The restricted geometry does not effect on the order of successive transformations in NH 4 HSO 4 but is accompanied by a significant reduction in entropy of phase transitions. The behavior of DTA-signal and permittivity show the expansion of the temperature range of the ferroelectric phase under hydrostatic pressure.

We present the results of both direct measurements and modeling of the intensive electrocaloric effect DT AD in ferroelectric triglycine sulfate under nonequilibrium thermal conditions and periodically varying electric field. In the narrow region around the phase transition temperature T C , a visible difference was observed between the electrocaloric responses at applying DT ON and removal DT OFF of the constant electric field: |DT ON | < |DT OFF | and |DT ON | > |DT OFF | at T < T C and T > T C , respectively. The variation of the frequency and profile of the periodic electric field at T < T C allowed one to obtain the gradual decrease in the average temperature of the top of the sample compared to the bottom kept at the constant temperature. At low frequency electric field, qualitative agreement was found between the time dependences of the measured experimentally and calculated DT values.Experimental and modeling studies of electrocaloric effect DT AD in triglycine sulfate showed that the applying/removal of a periodic electric field to/from the bulk sample decreases the average value of the waiving temperature of the top T top compared to T ¼ const of the bottom. Both frequency and duty cycle of the electric field impulses strongly affect T top .

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