$(NH_4)_3H(S0_4)_2$ and $Rb_3H(SO_4)_2$ single crystals, and $[Rb_{0.58}(NH_4)_{0.42}]_3H(S0_4)_2$ mixed crystal were grown and studied by measurements of dielectric constant and Raman spectra. We have confirmed the ferroelectric phase transition in $(NH_4)_3H(S0_4)_2$ and the tendency of antiferroelectric transition in $Rb_3H(S0_4)_2$.
However, $[Rb_{0.58}(NH_4)_{0.42}]_3H(S0_4)_2$ mixed crystal between $(NH_4)_3H(S0_4)_2$ and $Rb_3H(SO_4)_2$ was found to show a glassy freezing behaviour. In measurements of dielectric constant, the Curie-Weiss sharp peak of the ferroelectric transition disappeared. The imaginary part of dielectric constant was very similar to the famous dipole glass behaviour of $Rb_{\chi}(NH_4)_4 - _{\chi}H_2PO_4$. In Raman spectra, Raman spectral structures were not changed in the temperature range from 290K to 20K, indicating that the global lattice structural symmetry was conserved $[(NH_4)_{0.42}RB_{0.58}]_3H(S0_4)_2$ may thus be another example which shows a dipole glass transition due to randomly competing localized interactions, that is, dipole glass phase in the isolated hydrogen bonded system.
