The Second Ferroelectric Phase Transition in NaH3(SeO3)2 Crystals and their Physical Properties

Abstract

An investigation is made of the spontaneous polarisation, the coercive field, the dielectric constant, the electro‐optical behaviour, and the domain structure of ferroelectric NaH₃(SeO₃)₂ single crystals in the temperature range −195 to 0 °C. The existence of two phase transitions and two ferroelectric phases is confirmed; the presence of two domain systems and a contribution of this domains to the dielectric constant in the triclinic ferroelectric phase is observed. The multiaxial electrical behaviour of the crystals in this phase, the enantiomorphism of the domains, and other peculiarities of electrical twinning are discussed. A large difference is noted in the behaviour of the mutually orthogonal components of the spontaneous polarization.