Title: COEXISTENCE OF PARAELECTRIC/PROTON-GLASS AND FERROELECTRIC (ANTIFERROELECTRIC) ORDERS IN Rb_1-x(NH₄)_xH₂AsO₄ CRYSTALS

Authors: Z.Trybula, J.Stankowski (Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan, Poland)

TThis paper reviews the results of dielectric studies of the proton glass state in a mixed crystal Rubidium Ammonium Dihydrogen Arsenate (RADA) The coexistence of paraelectric/proton glass and ferroelectric or antiferroelectric orders, confirmed by other studies, has been discussed in detail. The phase diagram of RADA is asymmetric. The proton glass state exists for ammonium concentration in the range of 0.1<x<0.5. The phase diagram of deuterated DRADA is presented. The proton glass state region in DRADA, 0.2<x<0.35 is narrower than that for non-deuterated RADA. The effects of hydrostatic pressure on the dielectric properties in the proton glass state are presented. The glass temperature T_g decreases with pressure and is expected to vanish at 5 kbar. Low temperature behaviour is still an open question, since there is no experimental evidence of T_g(p) dependence below 4 K for proton glass systems.

Key words: domain structure, ferroelasticity
Comments: Figs. 23, Refs. 52, Tabs. 0.