Discovery of dipolar-glassy state in a newly found solid–solution system of C5NH6(BF4)1−x(PF6)x

Ferroelectric crystal of C5NH6BF4 and antiferroelectric crystals of C5NH6PF6 were found to form solid solutions C5NH6(BF4)1−x(PF6)x in the whole composition range, and a phase diagram of this binary system was derived by dielectrometry. The composition x was determined by using IR spectroscopy. The solid solutions exhibited dielectric dispersion at low temperatures in the composition range of 0.18≤x≤0.89, and showed, especially at the compositions of 0.41≤x≤0.65, only the dispersion without appreciable dielectric anomaly originating from the ferroelectric or antiferroelectric phase transition. The property of the dielectric dispersions showed striking similarity to that observed in the typical dipolar-glass system of Rb1−x(NH4)xH2PO4. It was concluded that the dipolar-glassy state was realized at low temperatures in this newly found solid–solution system in the composition range of 0.3<x<0.7 owing to frustration of the macroscopic, ferroelectric or antiferroelectric, orderings of ions.