Complex permittivity of the deuterated and undeuterated proton glass Rb1-x(NH4)xH2AsO4

Abstract

Dielectric measurements have been performed in both the deuterated and undeuterated proton glass rubidium ammonium dihydrogen arsenate Rb1−x(NH4)xH2AsO4 along the tetragonal a axis. Ammonium concentrations x of 0, 0.01, 0.05, and 0.10 were studied for the undeuterated sample, while ammonium concentrations of 0, 0.05, and 0.10 were studied for the deuterated counterpart. Glassy behavior is present for x=0.05 and 0.10 but could not be observed for lower ammonium concentrations. For x=0.05 and 0.10 we observed coexistence of paraelectric or proton-glass and ferroelectric order below the ‘‘glass transition’’ temperature Tg due to the random spatial fluctuations of the ammonium cation. Cole-Cole plots for the x=0.10 sample show that there is a distribution of relaxation times below Tg. This relaxation occurs in the proton-glass portion of the crystal. The activation energies corresponding to these relaxation processes are calculated.