The phase transitions in monoclynic RbD2PO4

The monoclynic form of RbD2PO4(DRDP) has two successive phase transitions: at TI-II=381 K and TII-III22 =311 K1. The superlattice structure occurs below TI-II (P21/m-P21/n)2. The typical antiferroelectric double hysteresis loops observing in the phase III is out of line with the polar group of symmetry of this phase (P21)2. The new phase IV is induced by the pressure higher than 0.7 GPa3.