The ferroelectric (FE) betaine arsenate (BA) and the antiferroelectric
(AF) betaine phosphate (BP) are structurally very closely related and
mixed crystals of BAxBP1-x can be grown over the whole concentration
range. The concentration (x) – temperature (T) – pressure (P) phase
diagram of the system is characterized by a transition from an AF to a
FE phase along with the appearance of some mixed regions on changing
concentration. Depending on concentration, one or two relaxation
processes appear in the low temperature region of the phase diagram.
Measurement of the hysteresis loops and the current curves have been
carried out along the (x-T-P)-phase diagram of this system. Multiple
loops have been observed in various regions of the phase diagram. The
correlation of the different contributions of the polarization and the temperature behavior of their critical fields with the main features of the
temperature and frequency dependent dielectric constant enables
clarification of the rich phase diagram obtained in this mixed
compounds in terms of the ferro- and/or antiferroelectric interactions
