L. N. Korotkov

Thermodynamic and Dielectric Properties of K1-x(NH4)xH2PO4 Mixed Crystal

We used the cluster pseudospin model for the K1−x(NH4)xH2PO4 type proton glasses, which takes into account the energy levels of protons near a PO4 groups (within the cluster approximation), the long-range interactions between the hydrogen bonds, and an internal random deformation field. We obtained a qualitative description of the temperature behavior of the order parameters, static dielectric permittivity, and the phase diagram of the K1−x(NH4)xH2PO4 compounds.

Dielectric and polarization study and phase diagram of K1-x(NH4)xH2PO4 system

Abstract T-x phase diagram of K1-x (NH4)x H2PO4 system is presented and the results of the dielectric and polarization study of K0.81(NH4)0.19H2PO4 mixed crystal are analysed. It is found out that in the crystal a glass-like phase transition takes place at 65 K and on further temperature decreasing the first-order phase transition is realized in the vicinity of ≃ 50 K.

Phase coexistence in mixed K1-x(NH4)xH2PO4 crystals

The dielectric permittivity and polarization measurements have been performed in mixed crystals K1-x(NH4)xH2PO4 (KADP-x%) with x = 0.19, 0.24, and 0.32. It was found out that the ferroelectric phase transition in KADP-19 is preceded by a mixed ferroelectric-paraelectric state. The coexistence of ferroelectric and proton-glass states in KADP-24 takes place at low temperature.

Dielectric properties of kdp-adp mixed crystals in the vicinity of ferroelectric phase transitions

Abstract

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.

Edwards-Anderson order parameter in proton glass of KDP-ADP system

The behaviour of the Edwards-Anderson order parameter qEA have been studied experimentally as the function of the temperature and time for K0.33(NH4)0.67H2PO4 mixed crystal in the vicinity of glass transition temperature. It was found a tendency of the qEA value to decay in time at the temperatures above the Vogel-Fulcher temperature.

Composition effect on glass-like properties of mixed crystals of KDP type with competing interaction

The analysis of dielectric and polarization properties of mixed ferroantiferroelectric crystals (1 −x )KDP-xADP and related systems has been performed for broad range of concentration x. The problems concerning the composition effect on spontaneous polarization, diffuseness of phase transitions, dynamics of proton glass transition and phase coexistence are discussed.

Nonequilibrium dielectric permittivity of K1−x(NH4)xH2PO4 solid solution

Abstract The dielectric and polarization study of K1−x(NH4)xH2PO4 mixed crystals has been made. In the crystals with 0.22 ≤ × ≤ 0.72 a transition to low temperature proton glass state is realized. It was found that the dielectric dispersion of proton glass compounds is well described by the Vogel-Fulcher law. The nature of a large thermal hysteresis of polarization in the mixed crystals (x ≤ 0.22) is discussed.

Dielectric, Elastic and Electromechanical Properties of K1-x(NH4)xH2PO4 Solid Solutions in Paraelectric Phase

Temperature dependences of dielectric permittivity ϵ33, piezoelectric constant d36 and elastic compliance S66 of K1-x(NH4)xH2PO4 ferro – antiferroelectric (FE - AFE) mixed crystals have been studied within temperature range 30 – 300 К. It was found a considerable contribution of the strain component x6 to polarization P3 near the FE transition temperature due to piezoelectric effect. Piezoelectric contribution to dielectric response in the vicinity AFE phase transition is weaker. It leads, in particular, to difference in the both shapes and positions of ϵ33 and S66 anomalies for K0,25(NH4)0,75H2PO4 single crystal near the transition temperature.

Dielectric, Electromechanical, and Elastic Properties of K1−x(NH4)xH2PO4 Compounds

We present the results of the thermodynamic theory of piezoelectric ferroelectrics and of the phenomenological theory of thermodynamic characteristics of the KH2PO4 type ferroelectrics. Available experimental data for the dielectric, piezoelectric, and elastic characteristics of the K1−x(NH4)xH2PO4 type systems are described using the proposed microscopic theory of these crystals.