Dielectric investigations show three anomalies for some Cs-1-x(NH4)(x)
HSO4 (x = 0.05, 0.1 and 0.25) compositions. The paraelectric-ferroelec
tric phase transition is well defined in the 280-320 K temperature ran
ge. A dipolar-type relaxation is observed only for x = 0.25. The high-
temperature phase transition is a plastic phase with highly orientatio
nal disorder.