Jaroslav Nosek

Scanning force microscopy of domain structures in Pb(Zn1/3Nb2/3)O3-8% PbTiO3 and Pb(Mg1/3Nb2/3)O3-29% PbTiO3

Domain structures of unpoled as well as poled (along [001]- and [110]-direction) Pb(Zn1/3Nb2/3)O3 (PZN)-8% PbTiO3 (PT) and Pb(Mg1/3Nb2/3)O3 (PMN)-29% PT single crystals have been investigated by scanning force microscopy (SFM) in the piezoresponse mode, at room temperature. Antiparallel domain structures have been detected mostly in unpoled crystals of both materials, with a fingerprint pattern in (001)-oriented PZN-8% PT crystal. The ferroelastic domain wall has been identified in poled (110)-oriented PZN-8% PT crystal. “Writing” of ferroelectric domains has been performed by applying a dc voltage to the SFM tip. Local re-poling has been observed for all unpoled as well as for poled (001)-oriented crystals at the voltage ±60 V. Local electrical switching was successful in poled (110)-oriented PMN-29% PT at higher voltage (±120 V) but was not successful in poled (110)-oriented PZN-8% PT crystal. Domain-engineered crystals poled in [110]-direction seem to exhibit more stable (in the sense of local re-polin...

Infrared and Raman spectroscopy of [Pb(Zn1/3Nb2/3)O3]0.92–[PbTiO3]0.08 and [Pb(Mg1/3Nb2/3)O3]0.71–[PbTiO3]0.29 single crystals

Far-infrared reflectivity spectra of [Pb(Zn1/3Nb2/3)O3]0.92–[PbTiO3]0.08 and [Pb(Mg1/3Nb2/3)O3]0.71–[PbTiO3]0.29 single crystals were investigated between 10 and 530 K, micro-Raman spectra were recorded between 300 and 800 K. No phonon softening was observed near either of the ferroelectric phase transitions. The low-frequency dielectric anomaly in the paraelectric phase is caused by contribution of dynamic polar nanoclusters with the main dispersion in the microwave range. Infrared and Raman spectra confirm the locally doubled unit cell (Zprim=2) in the paraelectric and ferroelectric phases due to the ordering in the perovskite B sites and occurrence of polar nanoclusters in the paraelectric phase. The lowest-frequency transverse optical (TO1) phonon mode active in the infrared spectra is underdamped in contrast to the recent result of inelastic neutron scattering, where no TO1 mode could be observed for the wave vectors q⩽0.2 A−1. This discrepancy was explained by different q vectors probed in infrared ...

A precise measurement of some nonlinear effects and its application to the evaluation of nonlinear elastic constants of quartz and GaPO/sub 4/

This paper deals with a precise measurement of amplitude frequency and intermodulation effects, and its application to the evaluation of nonlinear elastic constants of quartz and gallium orthophosphate (GaPO/sub 4/). An evaluation is based on the methods used previously concerning determination of the higher-order material constants in the quartz. Using a measurement of the intermodulation products and measurement of drive level dependence of resonant frequency of quartz resonators, we have determined some effective elastic constants of fourth order. The computer-based method of solution of the set of equations gives an access to obtain a number of effective nonlinear stiffnesses of fourth order. The measurements and computer solutions are performed on different Y-cuts resonators, both for quartz and gallium orthophosphate resonators, vibrating in fundamental thickness shear mode. The experimental results are discussed.

Contribution to the electromechanical and nonlinear properties of GaPO/sub 4/ crystals

In the last decade, much attention has been given to piezoelectric crystals with large electromechanical coupling coefficient. The quartz homeotypes berlinite and gallium orthophosphate (GaPO/sub 4/), along with the calcium gallo-germanates such as langasite are representative of these crystals. The coupling coefficient k/sub 26/ associated with thickness-shear mode resonators is two times greater than that of quartz, increasing the spacing between the series and parallel resonance frequencies of resonators suitable for the frequency range from 1 to 100 MHz. This is important for some types of crystal oscillators and monolithic filters. The large electromechanical coupling coefficient also increases the difference between the temperature dependencies of the fundamental resonance frequency and its harmonics. In this paper, measured resonance frequency-temperature characteristics of the fundamental and third harmonics of selected rotated Y-cut GaPO/sub 4/ resonators vibrating in the thickness-shear mode are presented. Further attention is given to the measurement of some nonlinear properties of rotated Y-cut GaPO/sub 4/ resonators. Knowledge of such nonlinear interactions is important for the analysis of intermodulation phenomena in resonators, and for the application of GaPO/sub 4/ resonators in crystal oscillators, filters and other electronic devices.

Contribution to the determination of high-order elastic stiffnesses from the measurement of BT-cut quartz resonators

The paper deals with the determination of the high-order constants possibility in the quartz using the measurement of the intermodulation products of the BT- and other cuts quartz resonators. The method is based on the Tierstens work (1983), which are provided on the AT-cut resonators vibrated in thickness-shear mode. The measurements performed on BT-cut quartz and other Y-cuts resonators given access to obtain of the effective non-linear constants of higher order. The experimental results and the comparison with the resonant method results are discussed.

Interferometric Measurement of the Temperature Dependence of Piezoelectric Coefficients for PZN-8%PT Single Crystals

Piezoelectrically induced displacements were measured by a laser interferometric method in the temperature range 150 K–333 K for two domain-engineered 0.92Pb(Zn1/3Nb2/3)-0.08PbTiO3 single crystals poled in the [001]-direction. Assuming an effective tetragonal symmetry, we determined the piezoelectric d31 coefficient by measuring the displacement on (100) and (110) crystal faces. Coefficient d31 = −1280 pC/N was calculated for the [100]-direction at room temperature. Its value is reduced to −550 pC/N at 210 K. Piezoelectric coefficient d31 measured on a second sample in the [110]-direction exhibited a smaller value than the previous one, only about –555 pC/N at room temperature and –360 pC/N at 190 K. Different domain structures in both samples might be the possible reason for this difference. Temperature dependence of piezoelectric coefficient d33 was also investigated. The effect of aging is also discussed. The domain configuration in crystals was observed by optical microscopy.

On the precision of a new laser interferometer in a wide temperature range

Abstract The paper deals with the construction of an interferometer, which works in a wide temperature range using a helium optical cryostat, and with the accuracy of the strain measurements. The suppression of cooling system vibrations is a necessary condition for the measurements. The precision of the strain measurements of different piezoelectric samples (such as PMN-PT single-crystals, PZT ceramics, etc.) is discussed.

Drive level dependence of the resonant frequency in BAW quartz resonators and its modeling

The influence of the excitation current on the resonant frequency and its mathematical description introduces a nonlinear impedance characteristic of the piezoelectric resonator. This influence was modeled by the nonlinear electrical equivalent circuit, in which the equivalent series resistance and equivalent motional capacitance are taken to be functions of the amplitude of the excitation current by means of the relations derived in the work. The equivalent circuit was analyzed by the method of equivalent linearisation. The relationships between the amplitudes of voltage applied on the AT-cut resonator and the first current harmonics or phase-frequency dependence of the excited resonator respectively, are derived. Amplitude jumps and dynamical temperature change phenomena are discussed.

Use of Various Zero Valent Irons for Degradation of Chlorinated Ethenes and Ethanes

Abstract Amongst all of the reducing agents that can be used in environmental remediation, zero valent iron (ZVI) is one of the most common due to its environmental acceptance, high reaction rate, good availability, and long-term stability. Moreover, ZVI mobility, stability and reactivity can be enhanced by the application of a DC electric current, ie electrokinetics (EK). In the study, six various slurries containing different ZVI were tested for their efficacy for chlorinated ethenes and ethanes degradation. Chlorinated compound concentrations, pH, oxidation-reduction potential (ORP) and conductivity were determined during the long-term kinetic test. Kinetic rate constants calculated for the degradation of three chlorinated ethenes (PCE, TCE and cis-DCE) concluded that EK brings substantial contribution to chlorinated compounds degradation. Nano-scale zero valent iron STAR had the highest reaction rates compare to the other ZVI tested. The performed study could serve as a preliminary assessment of various available ZVI before in-situ application.

APPLICATION OF NANOSCALE ZERO-VALENT IRON FOR GROUNDWATER REMEDIATION: LABORATORY AND PILOT EXPERIMENTS

It is known that the reductive effects of zero-valent iron (Fe0) and the sorptive capability of iron and its oxides can be used for both the dehalogenation of chlorinated hydrocarbons (CHC), especially of chlorinated ethenes (PCE → TCE → DCE → VC → ethene, ethane), and the removing of heavy metals from groundwater by turning them into a less-soluble form through changes of their oxidation state, or by adsorption. These consequences are being exploited in the construction of iron filling permeable reactive barriers for a longer time.1 The advantages of nanoscale zero-valent iron (nanoFe0) over the macroscopic one consist not only in the better reactivity implicit in their greater specific surface area but also in their mobility in rock environment.2,3 Numerous laboratory experiments, especially the batch-agitated experiments, with samples from seven various contaminated localities in Europe have been carried out with the aim to discover the measurement of the reductive effect of the nanoFe0 on selected contaminants. It was found that the nanoFe0 can be reliably usable as a reductive reactant for in-situ chemical decontamination of sites polluted by chlorinated ethenes (CEs), or hexa-valent chromium (CrVI). The rate of reductive reaction and the optimal concentrations for the real remediation action were determined. On the basis of these laboratory experiments, the methods for pilot application of nanoFe0 have been specified. Subsequently the pilot experiments were accomplished in surveyed localities.