Evidence of a low-temperature dipolar glass state in polycrystalline (NH₄)₃H(SO₄)₂

Detailed dielectric measurements are reported for polycrystalline (NH4)(3)H(SO4)(2) at temperatures 10 K < T < 100 K and frequencies 20 Hz < nu < 3 MHz. Instead of the ferroelectric phase transition expected at 63 K, a typical dipole glass transition was observed at around 60 K. The frequency dependence of the complex dielectric permeability at T < 50 K was well described by a sum of two Cole-Cole functions. One of the two relaxators provides a background contribution to the dielectric dispersion. The most probable relaxation time for the main relaxator was best fitted to the modified Arrhenius law with tau(0) = 3.5 x 10(-13)s,E = 50 K-gamma, and gamma = 0.37.