Influence Of Uniaxial Pressure Research Articles

Influence of Uniaxial Pressure on the Characteristics of Lamb and SH-wave Propagation in LiNbO₃ Crystalline Plates

Theoretical study of uniaxial pressure influence on the propagation characteristics of Lamb and SH-waves in lithium niobate plate is carried out. Electromechanical coupling coefficients and controlling coefficients of the pressure influence on phase velocity are calculated in various directions. Transformation and hybridization of acoustic modes upon a pressure influence have been derived in details. PACS: 43.25.Fe; 43.35.Cg; 77.65.-j

Electric behaviour of soft and hard lead zirconate titanate ceramics under electromechanical loading

ABSTRACTThe influence of uniaxial pressure (0 –1100 bars) applied parallel to the ac and dc electric field on the dielectric and ferroelectric properties of soft and hard PZT ceramics was studied in the temperature range from room temperature to 500°C. The results show that applying uniaxial pressure leads to a reduction of the peak intensity of the electric permittivity (ε) and its frequency dispersion. The peak intensity of ε becomes diffused and shifts with increasing pressure. The effective electric field Eeff and electrostrictive coefficient Q11 were evaluated from the obtained data. We explained our results based on the Cochran soft-mode, dielectric relaxation and a combination of de-aging and domain resulting processes from pressure.

Refractometry of Rb2ZnCl4 crystals under uniaxial pressure

The influence of uniaxial pressures applied along the main crystallophysical directions on the dispersion and temperature dependences of the refractive index n i of Rb2ZnCl4 crystals has been investigated. The n i value is found to be rather sensitive to uniaxial pressures, whereas uniaxial stress does not change the character of the dispersion and temperature dependences of n i. The pressure-induced changes in electronic polarizability αі, refraction R, and the parameters of UV oscillators are studied for mechanically deformed Rb2ZnCl4 crystals. The contributions of the UV and IR oscillators to the changes in n i at different temperatures, in different spectral regions, and under different mechanical stresses are estimated. The points of paraelectric–incommensurate–commensurate phase transitions (PTs) are found to undergo a significant pressure-induced shift to different temperature regions, depending on the pressure-application direction.

Influence of uniaxial pressure on dielectric properties of (1-x)Na0.5Bi0.5TiO3–xSrTiO3 for x = 0.01, 0.04, and 0.1 ceramics

Influence of uniaxial pressure on dielectric properties of (1-<i>x</i>)Na_0.5Bi_0.5TiO_3–<i>x</i>SrTiO₃ for <i>x</i> = 0.01, 0.04, and 0.1 ceramics

The influence of uniaxial pressures on thermodynamic properties of the GPI ferroelectric

The influence of uniaxial pressures on thermodynamic properties of the GPI ferroelectric

Influence of Uniaxial Pressure on Dielectric Properties and Aging Effect of BiFeO3 Ceramic

The external stress (0–1500 bar) dependence of dielectric properties and an aging effect of BiFeO3 ceramic has been investigated. The electric permittivity and dielectric losses first increased (up to about 700 bar) and next decreased with uniaxial pressure applied parallel to the ac field direction, while increased with the stress perpendicularly applied. It was suggested that combination of the de-aging, clamping of the domain walls, and the polarization reorientation mechanisms can be responsible for these changes. The aging effect is followed logarithmic law and is related to the relaxation of the domain structure towards an equilibrium configuration.

Densification and Microhardness of Spark Plasma Sintered ZrB2+SiC Nano-Composites

Ultra-High-Temperature Ceramics (UHTCs) such as ZrB2 and HfB2 with incorporation of SiC nanofiller are useful as structural materials for applications in propulsion and thermal protection systems such as turbine-engine hot section components, leading edge of hypersonic vehicles, where extremely high heat fluxes generate very high temperatures and steep temperature gradients [1]. Spark plasma sintering (SPS) technique is used for densifying the UHTCs under the influence of uniaxial pressure and pulsed direct current [2]. Here, we study the densification, grain growth, and microhardness of ZrB2 nanocomposites with 15% and 20% SiC consolidated using SPS.

Influence of Uniaxial Pressure on Elastic Waves Propagation in Piezoelectric Layered Structures "Y-cut langasite/fused silica"

Influence of Uniaxial Pressure on Elastic Waves Propagation in Piezoelectric Layered Structures "Y-cut langasite/fused silica"

Pressure changes of isotropic points in potassium-sulfate crystals

The influence of uniaxial pressures applied along the principal crystallographic directions on the dispersion and temperature dependences of the birefringence of potassium-sulfate crystals K2SO4 has been investigated. It has been found that the birefringence is quite sensitive to uniaxial pressures. The behavior of isotropic points has been analyzed, and temperature-spectral-baric diagrams of the isotropic state of the K2SO4 crystals have been constructed.

Influence of uniaxial pressure and aging on dielectric and ferroelectric properties of BaTiO3 ceramics

The effect of uniaxial pressure (0–3000 bar) applied parallel to the AC electric field and aging on dielectric and ferroelectric behavior of BaTiO3 ceramics were investigated. Applying uniaxial pressure leads to a reduction of the peak intensity of the electric permittivity (ε) of the polarization as well as of the dielectric hysteresis. The peak intensity of ε becomes diffused and shifts to a higher temperatures with increasing the pressure. The electrostrictive coefficient Q 11 and differential permittivity were evaluated from the obtained data. We interpreted our results based on the hardening of the soft-mode and domain switching processes under the action of pressure. The aging effect followed a logarithmic law and is related to the relaxation of the domain structure toward an equilibrium configuration. The aging rate was found to decrease with increasing frequency as a result of the pinning of polarization components by defects field.

An approach for studying the influence of uniaxial strain (pressure) on the temperature of the Bose–Einstein condensation of intersite bipolarons: Possible implementation for [formula omitted] cuprates

A universal approach is proposed to study the influence of strain (pressure) on the temperature of Bose–Einstein condensation of intersite bipolarons within the extended Holstein model. It is shown that uniaxial strain (pressure) derivatives of the temperature of such a Bose–Einstein condensation strongly depend on the arrangement of ions in the lattice. In particular, they may be positive or negative. A connection between the theoretically obtained results, along with the experimental data, on the influence of uniaxial pressure (strain) on Tc of RBa2Cu3O7−δ family cuprates is discussed.

Influence of Uniaxial Pressure on Dielectric Properties of the PLZT-x/65/35 (x = 11 and 13) Ceramics

Uniaxial pressure (0–1000 bars) effects on the dielectric properties of the PLZT-x/65/35 ceramic samples (x = 11 and 13) samples was investigated. The obtained results reveal that the applied stress largely changes the dielectric properties of these ceramics. Applying uniaxial pressure leads to a reduction of the peak intensity of the electric permittivity and a change of the frequency dispersion. Besides with increasing the pressure the ϵ-peak shifts to a higher temperature. The results show that applying the uniaxial pressure induces similar effects as increasing the Ti−ion concentration in PZT system. These effects can be connected with the change in domain structure under the action of combined electromechanical loading.

(RE)BCO Coated Conductor Joints in Dependence on Uniaxial Pressures

Abstract For practical use of ( RE )BCO coated conductors in power or AC applications, it is necessary to have reliable joining techniques. In order to reduce the magnetic losses in coated conductors the most promising approach is the filamentisation of the superconducting layer and subsequently the transposition of the percolation path by means of a joined second layer. Therefore, striated tapes are necessary which should be diffusively joined face-to-face at the edges with a reliable joining technique. We investigated the influence of uniaxial pressures on the performance of face-to-face Ag diffusion joints. For the joints we used tapes from SuperPower with 12 mm and THEVA with 10 mm width. The contact length was 3 cm. Pressures between 4 and 21 MPa were applied by means of a steel jacket. The tapes were annealed at 500iC in pure oxygen. The lowest average resistance was achieved at a pressure of about 12 to 17 MPa. The resistance of the as-pressed contacts shows a continuous decrease approaching a value of about 420 nΩcm¥ (SuperPower tapes) in the investigated pressure regime up to 21 MPa.

Uniaxial Pressure Effects on the Dielectric Properties of the PLZT-x/65/35 (x = 9.75 and 10) Ceramics

The influence of uniaxial pressure (0-1000 bars) applied parallel to the ac electric field on the dielectric properties of PLZT-x/65/35 ceramics (x = 9.75 and 10) was investigated. The results show that the applied stress has a significant influence on the dielectric properties of PLZT ceramics. Applying uniaxial pressure leads to the reduction of the electric permittivity (ϵ) peak and the frequency dispersion. Moreover, the peak of ϵ becomes diffuse and shifts to a higher temperature with increasing pressure. The results show that applying uniaxial pressure induces similar effects as the increase in Ti−ion concentration in the PZT system. We interpreted our results based on the domain switching processes under the action of combined electromechanical loading.

Effect of Electromechanical Loading on the Dielectric Properties of PLZT−x/65/35 Ceramics (x = 8 and 8.5)

The influence of uniaxial pressure (0-800 bars) applied parallel to the ac electric field on the dielectric properties of La−modified lead–zirconate−titanate ceramics with the Zr/Ti ratio of 65/35 was investigated. Applying uniaxial pressure leads to the reduction of the peak intensity of the electric permittivity (ϵ), of the frequency dispersion as well as of the dielectric hysteresis. The peak intensity of ϵ becomes diffuse and shifts with increasing the pressure. Our results show that applying uniaxial pressure induces similar effects as increasing the Ti−ion concentration in PZT system. We interpreted our results based on domain switching processes under the action of combined electromechanical loading. These studies clearly showed that the applied stress has a significant influence on the dielectric properties of perovskite ceramics.

Baric changes in refractive indices of K2ZnCl4 crystals

The influence of uniaxial pressure applied along the principal crystallophysical directions on the dispersion and temperature dependences of the refractive indices ni of K2ZnCl4 crystals has been investigated. The ni values are found to be fairly sensitive to uniaxial pressure, whereas an uniaxial stress does not change the behavior of the dispersion and temperature dependences of ni. The baric changes in ni have been studied. The electronic polarizability αi, refractions R, and parameters of UV oscillators (λ0i, B1i) of mechanically deformed K2ZnCl4 crystals have been calculated. The contributions of UV and IR oscillators to ni(λ) have been estimated for different temperatures, spectral regions, and stresses. A significant baric shift of the points of the paraelectric phase-incommensurate phase-commensurate phase transitions to different temperature ranges, depending on the direction of pressure application, is found; this shift is due to the effect of uniaxial stress on the K2ZnCl4 crystal structure.

Influence of combined external stress and electric field on electric properties of 0.5% Fe-doped lead zirconate titanate ceramics

Influence of uniaxial pressure (0–1000 bars) applied parallel to or perpendicularly to the ac or dc electric field (in one-dimensional or two-dimensional manner) on dielectric and ferroelectric properties of hard lead zirconate titanate (PZT) ceramics were investigated. The experimental results revealed that applying uniaxial pressure leads to a reduction in the peak intensity of the electric permittivity (ε), of the frequency dispersion as well as of the dielectric hysteresis. Moreover, with increasing pressure the peak intensity of ε becomes diffused and shifts to a higher temperature. It was also found that simultaneous application of uniaxial pressure and electric field (perpendicular to each other) in the poling process improves the ferroelectric properties. This indeed indicates new possibility for poling materials with a high coercive field and/or high electric conductivity. The effects of uniaxial load are weaker than that obtained for soft PZT ceramics. It was concluded that applying uniaxial pressure induces similar effects as increasing the Ti ion concentration in PZT system. The obtained results were interpreted through Cochran soft mode and domain switching processes under applying of pressure.

Influence of Uniaxial Pressure on the Phase Transition of Partially Deuterated Glycinium Phosphite

Influence of uniaxial pressure on the phase transition of glycinium phosphite crystal has been studied by measurement of the permittivity along the b-axis. The pressure was applied to the crystal along the three principal axes a*, b and c. It has a tendency that the phase transition temperature shifts towards lower temperature with increasing uniaxial pressure. The uniaxial pressure dependence of the each principal axes on the phase transition temperature of 75% deuterated GPI crystal is dTC D75%/dpa*= −0.07 K/kbar for the a* -axis, dTC D75%/dpb= −2.57 K/kbar for the b-axis and dTC D75%/dpc = −1.33 K/kbar for the c-axis, respectively.

Critical fields in easy-axis antiferromagnetics with allowance for Dzyaloshinski $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l} $$ interaction and uniaxial pressure

The easy-axis antiferromagnetic α-Fe2O3 is used to study the influence of uniaxial pressure on the magnetic phase diagrams. It is shown that there are regions where an abrupt and appreciable change in the magnetization is accompanied not only by a negligible change in the external magnetic field but also by a change in the uniaxial pressure. Thus, the situation usually achieved in magnetically soft materials arises, except that in this case it is controllable.

Electrical resistance of NbSe 3-single crystals under uniaxial pressure

The influence of uniaxial pressure along the a-axis on the resistivity along the b-axis of NbSe 3 single crystals was investigated. The pressure increases the CDW-transition temperature to near 59 K and suppresses both Peierls gaps. The increase of the pressure leads to enhancement of the superconducting transition. The resistance behaviour of NbSe 3-NbSe 3 junctions at low pressure reconciles with the Anderson localization mechanism of conductivity.