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A new form of biomineralization has been found in the pineal gland of the human brain. The crystals are 10 to 20 w m in length and have well-defined morphologies. Several structure types have been identified using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) showed that the crystals contain only the elements calcium, carbon and oxygen. Selected-area electron diffraction (SAED) and near infrared Raman spectroscopy established that the crystals are calcite. With the exception of the otoconia structure of the inner ear, this is the first report of the presence of non-pathological calcite in the human body. These microcrystals are believed to be responsible for the previously observed second harmonic generation (SHG) in pineal tissue samples and they may also exhibit piezoelectricity, suggesting a unique electromechanical biological transducer mechanism in the human brain.

AbstractRadiation-induced conformational disorder in ferroelectric P(VDF/TrFE)(75/25) irradiated in the paraelectric phase with fast electrons was studied using IR and NIR Raman spectroscopy and related to changes in dielectric relaxation. The observed radiation-induced changes in the intensity of bands characteristic of all-trans and trans-gauche conformations confirm the scission of long-range all-trans chain conformation. Electron irradiation modifies also the surface topography of the copolymer film: AFM studies of irradiated samples show a considerable increase in the surface roughness.

Relaxor-like behaviour was recently reported by Zhang et al. in P(PDF/TrFE) copolymers of (50/50) and (65/35) contents irradiated with high energy electrons in the paraelectric phase. To get more information on the nature of polymer relaxors we studied temperature dependence of complex dielectric permittivity of P(VDF/TrFE)(75/25) copolymer with Tc more distanced from the glass transition. Raman and IR spectra were used to characterize the conformational disorder.

Electroactive polymer films are widely applied in electroacoustic transducers and their properties can be tuned by matching the conditions of thermal treatment to the requirements of various devices. As the dielectric properties determine the piezoelectric response of the film we studied the effect of annealing at various temperatures on the dielectric dispersion of P(VDF/TrFE)(75/25) copolymer film. The most effective thermal treatment (in TC range) results in an increase in dielectric permittivity value and shifts the β-relaxation and piezoelectric resonance towards higher frequencies. The effect is related to the reduction of compensating charges piled up at the crystalline phase of the semicrystalline polymer. The heterogeneity of P(VDF/TrFE)(75/25) film annealed at temperatures in the TC range is also reflected in a complex acoustic response studied in one-side clamped conditions. Moreover, the room temperature sound velocity of the annealed copolymer film is considerably higher than that of non-annealed film.

We present the results for search of the best ceramic materials for electrostrictive transducers. We performed the following investigations: (1) investigation of different types of ferroelectric, antiferroelectric and non-polar complex oxides with perovskite (OPS) and tetragonal tungsten bronze (TBS) structures; (2) the investigations of the OPS with different degrees of the cations ordering; (3) the measurements of the electrostrictive coefficient Q, Curie-Weiss constant CW, coefficient of linear thermal expansion λ, polarization P and dielectric permittivity σr; (4) the X-ray analysis of the structure. The electrostrictive deformation may be very high and the relative strain can be of the order 10-3 in such materials.

Temperature dependence of the complex dielectric permittivity of [N(C2H5)4]2ZnCl4 crystal was measured in the frequency range 300 Hz / MHz. Jump-wise changes in the real and imaginary components of ε* were observed for the three crystallographic directions at the phase transition temperature. The dielectric dispersion clearly apparent in the high-temperature phase, rapidly disappears at the phase transition. The anomalous changes in the dielectric permittivity are related to vibrations of the tetraethylammonium ion. The activation energy of these vibrations amounts to 40 kJ/mol.

Dielectric behaviour and pyroelectric activity of rhodamine-doped PVDF films prepared by hot-pressing method were studied. Although the rhodaminedoping causes an increase of the abundance of all-trans conformation of PVDF, the pyroelectric sensivity is not improved due to doping-induced increase of the conductivity.

Temperature variation of pyroelectric response of P(VDF/TrFE) (75/25)-14 μm was studied in light modulation frequency range 1 Hz to 50 kHz at various excitation-response configurations. Since the dielectric behaviour of the film is involved in the dynamic pyroelectric characteristics important in the applications we measured also dielectric dispersion and thermally stimulated current. Pyroelectric coefficient p of the copolymer samples in form of diaphragm fixed on its perimeter does not depend on whether the positively, or negatively charged surface of the film is illuminated. Moreover, the p value is linearly dependent on the light modulation frequency f in the range 1-50 Hz and is frequency independent in the range 50 Hz - 1 kHz. The pyroelectric coefficient is constant in the temperature range 10°C - 100°C and thermal annealing causes a small decrease in the p-value.

0-3 type composites of triglycine sulphate, with high molecular weight polyethylene oxide were prepared by hot-pressing. FT Raman spectroscopy was used to control the interaction of glycine ions with the polymer. Pyroelectric and electric response was studied for composite samples in the form of diaphragm fixed on its perimeter and poled in low dc field (Ep = 6MV/m). Pyroelectric response in the current mode of TGS/PEO composites decreases on increasing the light modulation frequency. Pyroelectric coefficient evaluated for TGS/PEO composites at 10 Hz amounts to ∼ 7.10-5 C/m2K.

TSC and ε(T) was studied for SOLEF-25 μm polarized at various TP in EP=15-20 MV/m. Two high temperature TSC maxima were observed and related to the dipolar relaxation in α and β phases respectively. Increase of the ε after polarization is related to the nonpolar-polar transformation in α phase.

Deuterization of CsHSeO4 does not affect of the superionic phase transition but increases the activation energy in the superionic phase.

On the center region of cleavage surface of GASH (guanidinium aluminum sulfate hexahydrate) crystals grown at high temperatures, peculiar spiral domains have been observed by a powder deposition technique. Triangular etch pits found at the center of the spirals are direct evidence for the screw dislocation mechanism of crystal growth. Dislocations of high density are associated with the defects at the sites of crystallization water introduced during crystal growth at high temperatures. The formation model of the spiral domains are discussed on the basis of the spiral growth theory of crystal.

Ferroelectric domain structure of lithium ammonium sulphate single crystals is studied using scanning electron microscopy and electron microscope decoration technique. Domains of thickness 0. 1 / 80 μ are observed on various crystal surfaces; average domain thickness is found to be ≈30 μm. Domain walls are found to be parallel to b-orthorhombic axis.

The domain structure of GASH single crystals is investigated by scanning electron microscopy. Ferroelectric domains are observed only outside a central hexagonal zone which the dimension varies, it is shown that the main polarity of trapeziums outside this hexagon is alternatively positive and negative. Inside each of these trapeziums, ferroelectric domains of opposite polarity are observed. With the electron beam, negative domains can be nucleated only in a positive zone under special conditions. For interprete SEM pictures the electric conductivity inside and outside the hexagonal central zone is measured.

Dielectric and TSC studies of charged (by stabilized electrical breakdown) and discharged PVDF/PMMA blends have been performed. The relative changes in e? are found to decrease with increasing PVDF content except for samples with 50 and 70 weight-% of PVDF. The temperature Tmax of the TSC maximum is found to be shifted linearly towards lower temperatures with increasing PVDF content up to 30 weight-% of PVDF. For higher concentrations Tmax is found to be independent on PVDF content except for samples of 70 weight-% of PVDF. These behaviours indicate that for PVDF concentrations higher than 30 weight-% the system starts to lose its compatibility.

Complex impedance of Li(N2H5)SO4was measured in the frequency range 20 Hz\div500 KHz from 290 K to 455 K. Our results confirm the model of one dimensional protonic conduction with extrinsic barriers related with defects proposed by Schmidt et al.An activation energy of 0.48 eV is assigned to the extrinsic c-axis protonic conduction, whereas 0.35 eV refers to the intrinsic conduction. There is an indication of a structure change at ?433 K.

GASH single crystals grown at 40°, 60° and 70°C are obtained by static method at low supersaturation and investigated by scanning electron microscopy. In all these crystals antiparallel ferroelectric domain structures are observed outside a central hexagonal zone. With the electron beam, domains have been nucleated only outside this hexagone with variation of the conditions versus the growing temperature. On cleaved faces, hillocks are observed and analyzed.