Structural and dielectric studies of Rb-0.7(NH4)(0.3)HSO4 in its paraelectric and ferroelectic phases

The structural phase transition of the mixed compound Rb-0.7(NH4)(0.3)HSO4 is studied by differential scanning calorimetry and dielectric measurements . It is found that the transition occurs at 260 K to be of second order and ferro-paraelectric. The structure in the ferroelectric phase is determined at 183 K by means of single-crystal X-ray diffraction, of which the lattic e constants are determined as follows: a = 14.296(2) Angstrom, b = 4.587(3) Angstrom: c = 14.296(3) Angstrom, and beta = 118.00(2)degrees. The space g roup is confirmed to be P2(1) and the refined structure shows that the S-O bond lengths in the (HSO4-) groups seem to be slightly shorter than those o btained at room temperature in the paraelectic phase.