Hexagonal YMnO(3).
The crystal structure of hexagonal yttrium trioxomanganate has been determined at room temperature and at 180 K. It is isomorphous with LuMnO(3). The Mn displacement vector has a frustrated component in the ab plane and a ferroelectric part along the c axis. The net ferroelectricity is zero due to inversion twinning, with 1:1 twin fractions.
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