Phases in antiferroelectric-side Rb1-x(Nd-4)(x)D2AsO4 crystals studied by complex permittivity

Temperature and frequency dependent dielectric measurements in the mixed fe rroelectric (FE)-antiferroelectric (AFE) system Rb1-x(ND4)(x)D2AsO4 (DRADA- x) (for ammonium concentrations x = 0.39, 0.55 and 0.69) are reported for m easured fields along the a axis. These measurements, together with our prev ious light scattering results, confirm the phase coexistence of paraelectri c (PE) and antiferroelectric (AFE) phases in both x = 0.55 and 0.69 crystal s. Phase coexistence of deuteron-glass (DG) and antiferroelectric orderings is evidenced by the weak frequency dispersions (which occur below similar to 100 K) in both dielectric permittivities (epsilon'(a) and epsilon"(a)) f or the x = 0.39 crystal. The temperature-dependent data epsilon"(a) (f,T) p rove the existence of an electric dipolar relaxation process below similar to 100 K. The activation energy and attempt frequency corresponding to this relaxation process are calculated.