Disordered Structure of Ferroelectric Rubidium Hydrogen Sulfate in the Paraelectric Phase

抄録

We determined the paraelectric crystal structure of RbHSO₄ using X-ray diffraction intensities collected by an automatic four-circle diffractometer. One of the two independent SO₄ ions takes two molecular arrangements with equal probability while the other SO₄ ion occupies a single site. The ferroelectric structure is estimated from the disordered paraelectric structure to deduce a plausible spontaneous polarization. We conclude that the ferroelectric phase transition is driven by the disordering of the SO₄ ions. The H atom connecting these ions is located near one of the two SO₄ ions and executes large thermal motion. This result is interpreted by the riding model of the H atom associated with the disordering of the SO₄ ion.