S. A. Gridnev

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.

Anelastic and elastic infra-low freouency properties of ferroelastic crystals K(DxH1-x)3(SeO3)2.

Abstract The results of measurements of anelastic and elastic infra-low frequency properties of K(DxH1-x)3(SeO3)2 crystals at x=0; 0.7; 0.8; 0.85; 0.94 in the temperature range from 90 to 300 K at frequency of 10−4-10Hz are reported. The domain structure, lattice defects and crystal deuteration are shown to be responsible for the formation of mechanical hysteresis loops, the relaxation processes and shape memory effect.

Attenuation of low-frequency elastic oscillations in ferroelastic KH3(SeO3)2

Abstract Temperature dependences of internal friction Q −1 and shear modulus G at the frequency of ∼ 1 c/s of KH3(SeO3)2 crystals were studied by torsion pendulum technique in the temperature range from −190°C to+50°C. Two peaks were found on the Q −1(T) curves, the first in the vicinity of Tc and the second at −150°C related to the phase transition and loss domain mechanism respectively. The measurements show that below Tc Q −1(T) and G(T) the behaviour considerably depends on domain structure state. Shear elastic stiffnesses c 44, c 55 and c 66 above Tc have been calculated from experimentally found Gx , G y and G x . It was clarified that c 55 tends to zero when T ← T c . The basic experimental results are discussed in terms of phenomenological theory.

Low-frequency internal friction of h-bonded ferroelectrics

Abstract The internal friction of KDP-family crystals have been studied at the frequencies of some Hz. The experiments revealed a complicated temperature spectrum of mechanical losses which involved a few pronounced internal friction peaks of different nature.

PmP154. Newly developed multicomponent piezoceramic system for alternating pressure sensors

Abstract In multicomponent ferroelectric solid solution system based on PbZrO3 - (K0.5Bi0. 5)TiO3 with perovskite-type structure, successful results such as high piezoelectric modulus d33 ≃ (120–200)·10−12 C/N, wide operating temperature (250 – 300°C), suitable dielectric constant (150 – 550) and high piezoelectric modulus ratio d33/d31≃(3. 8 – 6. 5) have been obtained. Piezoceramics were used in diminutive sensors for the measurement of dynamic pressures.

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.

Relaxation of metastable states in incommensurate phase of Rb2ZnCl4

Dielectric relaxation in an incommensurate phase of Rb2ZnCl4 crystal has been studied after soliton structure equilibrium was disturbed by a temperature change and an application of alternating electric field. A temperature dependence of relaxation time is discussed in terms of mechanism of phase soliton pinning by point defects.

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.

Soliton and domain contributions to nonequilibrium dielectric permittivity of Rb2 ZnCl4

Abstract The temperature evolution of the nonequilibrium dielectric permittivity of Rb2ZnCl4 crystals has been investigated in the whole metastable state region in the commensurate phase at a frequency of 1592 Hz and an electric field strength from 0.3 V/cm to 200 V/cm. A soliton and a domain contribution to the nonequilibrium dielectric permittivity has been separated.