LiH3(SeO3)2: New Room-Temperature Ferroelectric

Abstract

Li${\mathrm{H}}_3$ ${\left(\mathrm{S}\mathrm{e}{\mathrm{O}}_3\right)}_2$ crystallizes in the monoclinic system and exhibits useful ferroelectric properties in the entire temperature range -196°C to 90°C. The spontaneous polarization and coercive field at room temperature are 15.0 μcoulombs/${\mathrm{cm}}^2$ and 1400 v/cm, respectively. X-ray examination reveals that the crystals belong to the space group $\mathrm{Pn}$, with cell dimensions $a={6.25}_8\mathrm{A}$, $b={7.88}_6\mathrm{A}$, $c={5.43}_3\mathrm{A}$, $\beta =105.2\mathrm{}°$, and two formula units per unit cell. The polar direction is perpendicular to the (001) plane. No Curie temperature could be observed. Na${\mathrm{H}}_3$ ${\left(\mathrm{S}\mathrm{e}{\mathrm{O}}_3\right)}_2$ is not isomorphous, but is ferroelectric below -79°C.