The results of investigations of porous glasses (PG) and porous glasses–ammonium hydrogen sulfate ferroelectric nanocomposites (AHS–PG) are presented. On the basis of dielectric and calorimetric measurements it was shown that in the AHS–PG nanocomposites with average pore size of 44, 68, 95, and 320 nm the anomalies of dielectric permittivity and specific heat similar to those in bulk crystals AHS are observed. An influence of the mean value of pores sizes on the ferroelectric phase transition temperatures of AHS nanocrystals embedded into the porous matrices was determined. It was shown that in AHS–PG dispersion of the dielectric permittivity is observed in both para- and ferro-electric phases and above room temperature AHS–PG nanocomposites exhibit the ionic conductivity.

The dielectric permittivity and the specific heat results of the ammonium hydrogen sulphate NH4HSO4 embedded into porous glasses with different average pore sizes in a wide temperature and frequency ranges are presented. The influence of the pore size on the ferroelectric phase transition temperature is considered. The results suggest a possibility of the size-effect influence on the phase transition type. The results show a good agreement with a theory [W. L. Zhong et al., Phys. Rev. B 50, 698 (1994)] indicating a non-monotonic behavior of the low-temperature phase transition with a confined particle.

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