X-RAY STUDIES ON SUCCESSIVE STRUCTURAL TRANSITIONS IN RBLISO4

Space groups and super-lattice structures of five phases of RbLiSO4 are investigated by X-ray diffraction method. Phase I (T> 204°C) is paraelectric (Pmcn-D126h). The incommensurate phase II (202<T<204°C) is characterized by a wave number kz=(2+δ)/5 with δ(T)=0.013(204°C)∼0.137(202°C). Phase III takes c=2c0 structure which belongs to P21/c11-C52h, where c0 is the cell dimension in phase I. The ferroelectric phase IV (166<T<185°C) belongs to P11n-C2s and takes c=5c0 super-structure. The I–II transition is 2nd order and the critical exponent is β=0.36±0.05, while other three transitions are 1st order ones. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.