PROTON-GLASS BEHAVIOR AND PHASE-DIAGRAM OF THE K1-X(NH4)XH2PO4 SYSTEM

Abstract

Both real and imaginary parts of the dielectric constants are measured in the pellet samples of K1-x(NH4)xH2PO4 [(KDP)1-x(ADP)x or (ADP-x] for a full range of mixing concentrations x from x = 0 to x = 1 at temperatures from room temperature to 15 K. Both ferroelectric and antiferroelectric phase transitions are observed for x < 0. 22 and x > 0.70, respectively, but proton-glass behaivor is observed in the range 0.28 < x < 0.64 and phase coexistences are observed for x of the phase boundary layers in the pressed pellet samples of KADP-x. Observation of the proton-glass behavior in the mixed-pellet system of KADP-x, which consists of microcrystalline grains, seems to confirm that the proton-glass phase may originate from a strong frustration in the short-range pairing of hydrogen bonds associated with randomly competing site interactions.