Photoelastic studies on ammonium Rochelle salt single crystal

Elastooptic measurements at room temperature on single crystals of ammonium Rochelle salt (ARS) which belongs to the Class 222 (D₂) of orthorhombic system and is isomorphous with Rochelle salt in its non-polar phase, have been made at 5890 Å. The values of all the photoelastic tensors, q_ij and p_ij of (ARS) at 5890 Å are reported. These constants have been determined from the measurements of relative and absolute path retardations produced in crystal prisms of various orientations when subjected to linear stresses using the birefringent compensator method and a modified form of Rayleigh refractometer respectively. The effect of hydrostatic pressure on the principal refractive indices and birefringences of (ARS) has also been deduced.     

Dielectric properties of porous aluminum oxide with inclusions of triglycine sulphate and Rochelle salt

The dielectric properties of composite structures based on porous aluminum with inclusions of triglycine sulphate and Rochelle salt were investigated. The effect of structured and adsorbed water on the dielectric behavior of the nanocomposite under study was found.     

Dielectric studies of nanoporous alumina films filled with the Rochelle salt

Dielectric studies of nanoparticles of the Rochelle salt embedded in pores of porous alumina have been performed in the temperature range from 80 K to the decomposition temperature of the bulk Rochelle salt. It has been revealed that the permittivity exhibits an anomaly corresponding to the lower structural transition to the paraelectric phase, whereas the upper ferroelectric transition is shifted above the decomposition temperature in agreement with the recently published data. The temperature of the lower transition for nanoparticles in pores is found to decrease by 10 K. Possible physical factors that can be responsible for the broadening of the region of existence of the ferroelectric phase have been discussed.     

Thermal conductivity of Rochelle salt

The temperature dependence of the anisotropic thermal conductivity of a Rochelle salt single crystal was investigated in different crystallographic directions in the range from −35 to +40°C. No anomalous behaviour was found near the Curie points.     

Proton dynamics in Rochelle salt

The investigation of the frequency spectra of Rochelle salt was performed by inelastic incoherent scattering of thermal neutrons using beryllium detector method. The neutron spectra were measured above the upper ferroelectric transition temperature at 307 K and in the polarized phase at 291 K, in the energy range 17–83 meV. Tentative conclusions concerning proton dynamics are drawn from the analysis of the spectra.     

Polarization relaxation in Rochelle salt crystals

The relaxation behavior of the domain structure of a Rochelle salt crystal during its repolarization by a static electric field was studied over a wide temperature range (from ?18 to +24°C). The field and temperature dependences of the relaxation time are found. It is shown that the difference between the activation energies determined far from and near the lower and upper phase transition points is due to the different mechanisms of interaction between domain boundaries and defects.     

Rochelle salt in an inhomogeneous electric field

The parameters of the hysteresis loop in the ferroelectric Rochelle salt were investigated using a sample with two pairs of electrodes: measurement electrodes and the side ones. It has been shown that the difference between the potentials of the measurement and the side electrodes (generating an inhomogeneous electric field) leads to gradual decay in time t of the remanent polarization P_r. The time required for the hysteresis loop to disappear in the inhomogeneous electric field (not parallel to the ferroelectric axis) decreases with temperature increase from 44±3 h at – 9°C to 2.3±0.1 h at 21.9 °C. On the other hand, the crystal placed for a sufficiently long time simultaneously in the measuring electric field and in the constant inhomogeneous one may finally exhibit a stationary hysteresis loop with a reduced remanent polarization and the unchanged coercive field. It has been shown that the crystal as a whole does not have to be polarized perpendicularly to the ferroelectric axis in order for its hysteresis loop to be reduced.     

季氨盐对KDP晶体的光学特性影响

 生长了不同季氨盐掺杂浓度的KDP晶体，其锥光干涉实验显示了晶体的内应力引起的双折射和双轴晶特性较明显。透过率特性的实验结果表明，不同浓度的季氨盐对KDP晶体的光学均匀性有较大影响。报道了掺季氨盐0.001%的KDP晶体的异常光学透过率特性以及晶体具有三维变化的波片效应和旋光特性。     

On the specific heat anomaly in ferroelectric Rochelle salt

The temperature dependence of the “ferroelectric” contribution to the specific heat in Rochelle salt has been calculated for the two sublattice model. In contrast to single order parameter models it is found that the specific heat anomaly has the same sign at the lower and at the upper Curie point.     

Dielectric relaxation in deuterated triglycine sulfate crystals

A study has been made of the slow relaxation of the dielectric permittivity of deuterated triglycine sulfate (DTGS) initiated by application of a dc electric field. The field and temperature dependences of the relaxation time associated with domain-wall motion were obtained. The effect of the internal electric field on relaxation processes is seen in different behavior of the field and temperature dependences under different orientations of the external field. The existence in DTGS crystals of two temperature regions of domain-structure rearrangement lying 7–8 and 15–18 °C below the Curie point has been established. Fiz. Tverd. Tela (St. Petersburg) 40, 1542–1545 (August 1998)     

Dielectric and transport properties of a supercooled symmetrical molten salt

The liquid-glass transition of the restricted primitive model for a symmetrical molten salt is studied using mode-coupling theory. The transition at high densities is predicted to obey the Lindemann criterion for melting, and the charge-density peak found in neutron-scattering experiments on ionic glass formers is qualitatively reproduced. Frequency-dependent dielectric functions, shear viscosities, and dynamical conductivities of the supercooled liquid are presented. Comparing the latter to the diffusion constant, we find that mode-coupling theory reproduces the Nernst-Einstein relation. The Stokes-Einstein radius is found to be approximately equal to the particle radius only near the high-density glass transition.     

Dielectric properties of thin films of partially deuterated betaine phosphite with large- and small-block structures

Ferroelectric thin films of partially deuterated betaine phosphite (DBPI) have been grown by evaporation on NdGaO₃ substrates with a preliminarily deposited structure of interdigitated electrodes. The block structure of the films is a texture in which the polar axis b is oriented in the plane of the film and the a* axis is perpendicular to this plane. Typical dimensions of the single-crystal blocks in DBPI films substantially exceeds the distance between the interdigitated electrodes (d = 50 μm). However, DBPI films in which the block structure has characteristic dimensions of the order of d have also been grown. Investigations of the dielectric properties of the films have demonstrated that the dimensions of the block structure have little effect on the behavior of a small-signal dielectric response, which, in the phase transition region, is characterized by a strong anomaly of the capacitance of the structure at T = T _c and by a glass-like behavior of the capacitance C and dielectric loss tangent tanδ in the temperature range of 120–200 K. By contrast, the low-frequency strong-signal dielectric response (dielectric hysteresis loops) in the structures with small blocks differs significantly from that observed for large-block structures. The difference in the frequency behavior of the hysteresis loops in the large-block and small-block structures is associated with the limitation of motion of domain walls in the case of small blocks.     

Piezoelectric resonance in Rochelle salt: The contribution of diagonal strains

Within the framework of two-sublattice Mitsui model with taking into account the shear strain ε₄${\epsilon }_4$ and the diagonal strains ε₂${\epsilon }_2$ and ε₃${\epsilon }_3$, a dynamic dielectric response of Rochelle salt X-cuts is considered. Experimentally observed phenomena of crystal clamping by high frequency electric field, piezoelectric resonance, and microwave dispersion are described. Analytical expressions for the resonant frequencies of these cuts, associated with the shear vibration mode of ε₄${\epsilon }_4$ and with the extensional in-plane modes of ε₂${\epsilon }_2$, ε₃${\epsilon }_3$, are derived. It is shown that the lowest resonant frequency is always associated with the ε₄${\epsilon }_4$ shear mode.     

Phase matching characteristics of deuterated ammonium dihydrogen phosphate crystals

Refractive indices for crystals ammonium dihydrogen phosphate(ADP), 30% deuterated ADP(DADP), 50%DADP, and 70% DADP are measured from 253 to 1529 nm with 5 × 10-6accuracy. Numerical fits to modified double-pole Sellmeier equation are made. Second-harmonic generation, third-harmonic generation phase matching(PM) angles, and noncritical PM(NCPM) wavelengths are calculated using the Sellmeier parameters. The deuterated crystals show smaller PM angles than pure crystal. Fourth-harmonic generation process can be realized by DADP in smaller deuterium content than deuterated potassium dihydrogen phosphate(DKDP).The measured NCPM wavelengths are consistent with the calculated value. PM characteristics are compared between DADP and DKDP.     

Dielectric properties of single-crystal deuterated triglycine sulfate (DTGS) in ultra-weak low-and infra-low-frequency electric fields

The complex permittivity ɛ* is studied with separate readings for ɛ′ and ɛ″ at low and infralow frequencies and ultraweak fields. The effective conductivity λ is determined. An Arrhenius dependence is observed for ln ɛ′(1/T), ln ɛ″(1/T), and ln λ(1/T), both in the paraphase and in the polar phase. It is proposed that the conductivity of crystalline DTGS in the paraphase is an ion jump conductivity. Fiz. Tverd. Tela (St. Petersburg) 41, 1073–1075 (June 1999)     

Phase transitions of Rochelle salt as studied by high-resolution heat capacity measurements

The heat capacity of single crystal Rochelle salt has been measured from 190 to 308 K by a high resolution adiabatic calorimeter. The anomalous heat capacity is positive and equal to + 1.0 ± 0.1 JK^?1mol^?1 at both of the Curie points. A graphical comparison of the present data and four previously published sets of heat capacity data is presented. They are consistent with each other to within 1% except in the transition regions where positive and negative anomalies as well as no anomaly at all have been reported by different authors. The present data agree with the electrocaloric and piezocaloric experiments and with the prediction from the Ehrenfest relation.No heat capacity anomaly was found at 212 K where another phase transition has been reported by submillimeter spectroscopy.     

Effect of electric field on the longitudinal ultrasonic waves in Rochelle salt

The temperature dependence of velocity and attenuation for the longitudinal ultrasonic waves propagating along the (100) direction has been measured in the vicinity of the upper transition temperature under the various electric conditions in Rochelle salt.     

On order parameter fluctuations in Rochelle salt detected by Brillouin scattering

In both of the nonpolar phases of ferroelectric-ferroelastic Rochelle salt frequency and linewidth of the quasilongitudinal acoustic phonon propagating along [011] have been investigated in a high resolution Brillouin- scattering experiment. Softening and damping of this mode can be quantitatively explained by a piezoelectric coupling to the fluctuations of the polarization along the ferroelectric axis, P₁.