Proton glass state in KH2PO4-NH4H2PO4 mixed crystals

In mixed crystals K1-x(NH4)xH2PO4 (KADP) over the concentration range 0.22 ≤ x ≤ 0.70 at low temperatures a dynamic transition into a proton glass state has been studied. It was found that proton glass state is characterized by specific dispersion of dielectric permittivity with a very wide distribution of relaxation times, irreversibility of electric polarization, very slow dielectric relaxation and nonequilibrium electric properties. The change in the dielectric thermal hysteresis and in the form of P(E) hysteresis loops in the mixed (x = 0.19) crystals below Curie point (Tc) indicates the coexistence of ferroelectric and proton-glass phases as well as paraelectric and ferroelectric phases.

Keywords:

• mixed crystals
• ferroelectrics
• antiferroelectrics
• proton glass
• dielectric dispersion
• relaxation
• irreversibility of polarization