Effect of a restricted geometry on thermal and dielectric properties of NH₄HSO₄ ferroelectric

ABSTRACT

Heat capacity, thermal dilatation, sensitivity to pressure and permittivity of NH₄HSO₄ 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 NH₄HSO₄ in nanocomposites and to the phase transition temperatures change. The restricted geometry does not effect on the order of successive transformations in NH₄HSO₄ 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.

KEYWORDS:

• Ferroelectric
• phase transition
• porous glass
• nanocomposite

PACS NUMBERS:

• 62.50.-p
• 65.40.-b
• 77.80.Bh
• 62.23.Pq
• 65.80.-g

Acknowledgments

We are grateful to Dr. Maxim Molokeev for X-ray characterization of the samples.

Funding

The reported study was partially supported by the Russian Foundation for Basic Research (RFBR), research project No. 16-32-00092 mol_a.