P. Hana

Study of Flexoelectric Phenomenon from Direct and from Inverse Flexoelectric Behavior of PMNT Ceramic

Flexoelectric phenomenon describes creation of electric polarization in non-conducting solids by applying of gradient of deformation. The inverse flexoelectric phenomenon describes the generation of a mechanical deformation in an insulating solid by an applied gradient of the electric field. Lead magnesium niobate-lead titanate (PMNT) ceramic permits study of the flexoelectric behavior because of its large flexoelectric coefficient. Special conical samples were prepared for the generation of a high electric field gradient and cylindrical samples with uniform field. Theoretical study of flexoelectric phenomenon seems to be very interesting in the last time because it was confirmed from direct (polarization caused by gradient of deformation) and from inverse behavior (deformation developed from gradient electric field) outgoing from thermodynamic theory.

Study of the Inverse Flexoelectric Phenomena in Ceramic Lead Magnesium Niobate-Lead Titanate

The inverse flexoelectric phenomenon describes the generation of a mechanical deformation in an insulating solid by an applied gradient of the electric field. Lead magnesium niobate-lead titanate (PMNT) ceramic permits study of the inverse flexoelectric behavior because of its large flexoelectric coefficient. Special conical samples were prepared for the generation of a high electric field gradient and cylindrical samples with uniform field. A strong deformation is caused by the electrostrictive behavior of PMNT ceramic. An asymmetric butterfly-shaped strain dependence on electric field is observed at wide temperature range on the conical samples. For evaluation of converse flexoelectric coefficient μ 33 (in matrix notation) it is necessary to know elastic properties of ceramic. The ultrasonic measurements on ceramic samples were performed for this purpose. In this letter we also report measurements of temperature dependence of flexoelectric coefficient μ 33 . The measurements confirmed a great enhancement of μ 33 coefficient in PMN ceramics, which cannot be explained exclusively by the high permittivity of the ceramic.

Piezoelectric, dielectric and pyroelectric properties of 0-3 ceramic-polymer composites

Abstract The circular samples of composites were made from PZT ceramic grains dispersed in polymers (epoxy or rubber). Pressure dependencies of the hydrostatic piezoelectric coefficient dh and permittivity ε were measured in the range up to 60 MPa. The hydrostatic strain coefficient dh, the hydrostatic voltage coefficient gh and figure of merit dh.gh were determined using the static method. The pressure dependence of the hydrostatic coefficients was measured for several successive cycles. Experimental dependence of the charge on pressure and temperature was fitted by multi parameter function. The pressure and temperature dependencies of the hydrostatic dh and pyroelectric p3 coefficients were determined. It was found that the hydrostatic strain coefficient dh and hydrostatic voltage coefficient gh decreased and pyroelectric coefficient p3 increased with pressure at constant temperature.

Dielectric Properties of PZN-PT Single Crystals Influenced by Electric Field in a Wide Temperature Range

The paper deals with phenomenological treatment of Lead Zinc Niobate—Lead Titanate (PZN:PT) crystals. Polarization and weak field permittivity as functions of temperature and bias electric field throughout the whole phase transitions range are of particular importance for the PZN-PT compositions behaviour close to the morphotropic phase boundary (MPB). The effect of DC bias field on phase transitions in PZN:PT solid solutions near the MPB was studied. A phase transition induced by electric field and associated changes in dielectric properties of PZN:PT were observed for different compositions of 4.5% and 8% PT. Relaxation behaviour was observed, too.

Elastic Stiffness Constants of PZN-4.5%PT Single Crystal Influenced by DC Bias Electric Field Applied at Various Directions to Prototypic Crystal Symmetry

The purpose of this work was to characterize an influence of the electric bias field on the elastic stiffness constants of important and unusual piezoelectric material Lead Zinc Niobate-Lead Titanate (PZN-PT). The longitudinal and transverse mode of sound propagation in single crystals containing 4.5% PT were studied. The influence of electric field, which poles the sample, is investigated by the pulse-echo sound propagation technique. From these measurements, the values of complex elastic stiffness constants are evaluated at different poling conditions with different frequencies for longitudinal and sheer excitations. Crystal cuts [001], [110] and [111] served for measurements of the elastic stiffness constants under application of the electric field. Aspects of field-induced phase transitions in PZN-4.5%PT single crystals at room temperature are discussed. Hysteretic behavior has an influence on attenuation and velocity of ultrasound.

Effect of Electric Field on Hydrostatic Piezoelectric Coefficients of Single Domain PZN-PT Crystals

The effect of dc bias electric field on the hydrostatic piezoelectric coefficient dh in Lead Zinc Niobate-Lead Titanate (PZN:PT) single crystal solid solutions in the vicinity of the morphotropic phase boundary (MPB) is studied. The hydrostatic measurements can be very important to gain insight into these materials. In particular, the discrepancy between sum of piezoelectric coefficients d33+ 2 d31 vs. hydrostatic dh coefficient measured directly suggests the importance of extrinsic contributions. Limiting values of measured hydrostatic piezoelectric coefficients dh for high electric fields are compared with calculated theoretic values from the Landau-Devonshire-Ginzburg (LGD) phenomenological theory. The influence of complicated microstructure within the single domain region is studied. Such microstructure could possibly account for the inability of the LGD phenomenology to give correct electric field bias dependence of dielectric constant.

Dielectric and Piezoelectric Properties of Sn2P2S6 Single Crystals

Abstract Dependence investigations of the hydrostatic piezoelectric coefficient (d h ) and the dielectric permittivity (ϵ) on pressure (p) are presented. Calculations of the voltage piezoelectric coefficient g h (p,T) are made. It was determined, that Sn2P2S6 single crystal has large values of coefficient (g h ). That allows us to use Sn2P2S6 single crystals as piezoelectric sensors in the wide temperature and pressure range.

Non-Linear Hysteresis Properties of PZT Ceramics

The paper deals with the dynamic measurement of the hydrostatic piezoelectric coefficients of Pb(Zr x Ti1 − x )O 3 (PZT) piezoelectric ceramics. The non-linear phenomena as the influence of a DC electric field on the hydrostatic voltage coefficient g h of a PZT sample was studied at various temperatures. Values of the coercive field were determined and compared with ones obtained from polarization vs. electric filed P(E) hysteresis loop measurements. Using the LVDT sensor, the deformation vs. electric field S(E) hysteresis loop, measured in the wide temperature range, was provided too. A noticeable influence of the temperature on coercive field values was exhibited both for hard and soft PZT ceramics (APC 841 and APC 856).

The Investigation of Dynamic Piezoelectric Properties of Sn2P2S6 Single Crystals

Investigations of the dependence of the piezoelectric coefficients d h and g h on hydrostatic pressure p and temperatures are presented. Two anomalies of the piezoelectric coefficient d h are observed at □ 1 ≈ 315 □ and □ 2 ≈291 K. They are assigned to a tricritical and triple point in the p-T diagram of Sn 2 P 2 S 6 . The large values of d h and g h in Sn 2 P 2 S 6 allow us to use them as piezoelectric sensors in a wide temperature and pressure range. * Paper originally presented at 10th European Meeting on Ferroelectricity, Cambridge, U.K., August 3–8, 2003. † E-mail: tyagur@mail.uzhgorod.ua ‡E-mail: iryna_tyagur@vslib.cz

PIEZOELECTRIC HYDROSTATIC COEFFICIENTS OF PVDF AND P(VDF-TRFE) COPOLYMER FOILS AT HIGH HYDROSTATIC PRESSURES

Abstract Pressure dependence of the hydrostatic piezoelectric coefficient dh was measured for PVDF and P(VDF-TrFE) polymer foils in the range up to 60MPa. The hydrostatic strain coefficient dh, the hydrostatic voltage coefficient gh and figure of merit dh·gh were determined using the static method. Electric charge induced across samples was measured by Keithley 6517 electrometer and the pressure in the measuring chamber was changed by using a home made hydraulic press. The pressure dependences of hydrostatic coefficients were measured for several cycles. A pressure hysteresis was observed there. Permittivity of the polymer foils was measured as a function of pressure using an HP 4192A Impedance Analyser. Experimental dependences of the charge on pressure and temperature were fitted by multi parameter function. The pressure and temperature dependences of the hydrostatic dh and pyroelectric p3 coefficients were determinated. It was found the hydrostatic strain coefficient dh decreased and pyroelectric coeff...