PROTON-GLASS DIELECTRIC BEHAVIOR AND PHASE-DIAGRAM OF CS1-X(NH4)XH2ASO4

The complex dielectric constants of mixed Cs0.80(NH4)0.20H2AsO4 single crystals have been measured in the temperature range from 13 to 200 K and the frequency range from 4.4 to 624 kHz along the a and c axes. P roton-glass behavior is first observed in the low-temperature region. The asymmetric concentration-temperature (x-T) phase diagram is obtain ed by measuring the complex dielectric constants of mixed Cs1-x(NH4)xH 2AsO4 microcrystalline powder pellets for the full range of mixing con centration x from 0 to 1. Proton-glass behavior develops in the concen tration range of 0.12 < x < 0.51. Coexistence of the proton-glass phas e with the respective long-range ordering is observed in the two phase boundary regions.