Complex permittivity of the deuterated and undeuterated proton glass Rb1-x(NH4)xH2AsO4
Schmidt, V. Hugo
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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.
F.L. Howell, N.J. Pinto, and V.H. Schmidt, “Complex permittivity of the deuterated and undeuterated proton glass Rb1-x(NH4)xH2AsO4,” Phys. Rev. B 46, 13762-13766 (1992).