L. Kozielski

PZT Microfibre defect structure studied by Raman spectroscopy

Raman-scattering spectroscopy on the microscale is proposed as a method to study the distribution of defects and existing vacancies in lead zirconate titanate (PZT) fibres during industrial processes to monitor the volumetric structural order within the fibre and to estimate the spatial phase transition degree from rhombohedral to tetragonal phase.PZT fibres developed in two different sintering atmospheres, PbO and a mixture of PbZrO3 and ZrO2 (PZ+Z), were studied to determine optimal conditions for the production of defect-free PZT fibres. An estimation of defect distribution along the radius of the PZT fibres is presented using Raman spectroscopy and confirmed by x-ray-diffractometry measurements. The degradation of the spatial-mechanical properties is explained by structural changes produced by electrostatic interactions between Zr and Ti ions.

Structure and dielectric properties of PZT-type ceramics with the diffuse phase transition

In the present work the (Pb0.84Ba0.16)(Zr0.54Ti0.46)O3 (PBZT) solid solution has been synthesized. The process of preparation was investigated by simultaneous thermal analysis (STA) and X-ray diffraction method. The hot pressing method was utilized for densification of ceramic samples. Dielectric properties of donor- and acceptor-doped PZT-type ceramics were measured within the temperature range including the phase transition region. Frequency-dependent relaxation behaviour in PBZT ceramics was found. The structural phase transition at T = (517 ± 3) K was determined by X-ray diffraction method. Arrhenius plot of total conductivity derived from ac impedance spectroscopy measurements was used for characterisation of phase transition. Changes in activation energy were found characteristic of phase transition in PBZT ceramics.

Raman spectroscopy of Pb(Zr1 − x Ti x )O3 graded ceramics around the morphotropic phase boundary

Lead zirconate titanate ceramics Pb(Zr1–x Ti x )O3 with spatially graded composition from X = 46 to 49 were studied by Raman scanning microscopy and the results were compared with Raman spectra in PZT ceramics of different compositions around the morphotropic phase boundary (MPB). An E-symmetry mode located near 200 cm−1 was found to be a measure of the tetragonality of PZT in both standard graded ceramics. The singular value decomposition method was applied to decompose the experimental spectra of the graded ceramics. Two main contributions were found: one is related to the intensity of the main transverse modes – especially the E(TO2) mode – and it gives evidence of the change between tetragonal and rhombohedral symmetries in the sample; the second one shows changes just through the spatial MPB and it is related to the intensities of A1(TO2) and E(LO2) modes. All the phonons involved in the main changes correspond to Zr and Ti vibrations.

Influence of sintering conditions on relaxor properties of BaBi2Nb2O9 ceramics

The main purpose of present studies is to learn the effect of sintering temperature on BaBi2Nb2O9 (BBN) ceramics properties. Grain structure analysis performed by the scanning electron microscope (SEM) exhibits differences in grain structure of the ceramics sintered at various temperatures for a constant time. Namely, the grain sizes increase with the increase of the sintering temperature. This fact is connected with changes in dielectric properties. The maximum of the real part of permittivity ( ) and corresponding temperature (T m) shifts to higher values. The properties characteristic for the ferroelectric relaxors also yield to change. The ceramics sintered in higher temperature revealed lower frequency dispersion of and T m. It should also be noticed that the freezing temperature and the Burns temperature have changed. These results indicate that the behaviour of the relaxor ferroelectrics is weakened by the increase in the grain size.

Dielectric, Pyroelectric and Thermally Stimulated Depolarization Current Investigations on (Ba, Sr)TiO3 Ceramics with Bi2O3 Additive

The Ba1−x Sr x TiO3 materials have received increased attention as one of the most important materials for electroceramic components, such as high dielectric ceramic capacitors, tunable phase shifters and PTCR. In this paper the effect of 0.5; 1; 1.5; and 2 mole% of Bi2O3 addition on microstructure, structure, dielectric properties (i.e., dielectric constant ϵ′, and dielectric loss factor tan δ), as well as pyroelectric and thermally stimulated depolarization currents (TSDC) of (Ba0.8Sr0.2)TiO3 ceramics have been investigated. The distinct correlation between Bi2O3 content, wide maxima in TSDC, anomalies in ϵ′ (T) and tan δ (T) characteristics occurring within the range of the paraelectric phase was confirmed. Changes of electric conductivity and Seebecks coefficient, caused by Bi2O3-additives, were also studied.

Light-intensity-induced characterization of elastic constants and d33 piezoelectric coefficient of PLZT single fiber based transducers.

Enhanced functionality of electro-optic devices by implementing piezoelectric micro fibers into their construction is proposed. Lanthanum-modified lead zirconate titanate (PLZT) ceramics are known to exhibit high light transparency, desirable electro-optic properties and fast response. In this study PLZT fibers with a diameter of around 300 microns were produced by a thermoplastic processing method and their light-induced impedance and piezoelectric coefficient were investigated at relatively low light intensity (below 50 mW/cm2). The authors experimentally proved higher performance of light controlled microfiber transducers in comparison to their bulk form. The advantage of the high surface area to volume ratio is shown to be an excellent technique to design high quality light sensors by using fibrous materials. The UV absorption induced change in elastic constants of 3% and 4% for the piezoelectric coefficient d33.

Impedance Spectroscopy of BaBi2Nb2O9 Ceramics

Investigations presented in the present work are concerning the other member of the Aurivillius family, the BaBi2Nb2O9 (BBN). This compound, which seems to be very interesting from the potential applications point of view. The dielectric characterization of this materials and influence of sintering condition on grain structure and properties of those materials had been very widely described in our previous paper. Now we would like to present the hitherto unreported electric properties of BaBi2Nb2O9 ceramics, investigated by the impedance spectroscopy (IS). IS is nondestructive method, which allows to separate grain and grain – boundary effects due to the different frequencies of the relaxation process in grain and grain boundaries. This enables us to determine the temperature dependences of grain (Rg) and grain-boundary (Rgb) resistance and evaluate their respective activation energies (Ea). Additionally a comparison between macroscopic results obtained by Impedance Spectroscopy and miroscopic direct local LC-AFM conductivity measurements are presented.

Microstructural and electromechanical comparison of different piezoelectric PZT based single fibers and their 1–3 composites

In this work, single PbZrTiO3 fibers were produced by a thermoplastic extrusion process. Afterwards, green fibers were sintered under PbO and PbZrO3+ZrO2 atmosphere and revealed single fibers and their 1–3 composites were analyzed and compared regarding electromechanical properties. The 1–3 composites show a higher coercive field. Microstructure of the sintered fibers and phase compositions across their diameter were investigated as well.

Mechanical examination of PZT microfibre defects structure

The major problem in the production process of efficient ultrasonic transducer is the preparation of defect-free PZT fibres. A considerable amount of empirical work is presently in progress to achieve this goal of special importance for high-sensitive transducers. However, there is a lack of basic research on the detection of residual stress and defects areas in these fibres due to difficulties in mechanical examination of such flexible elements. This work presents use of the nanoindenter for material characterisation of PZT fibres of 140 µm radius obtained by extrusion method. The sudden depth-excursions during indentation on the edge of fibres have been clarified using Piezoresponse Mode Atomic Force Microscopy method and XRD measurements. The nanoindentation method proves to be the efficient tool capable to detect contribution of defects along the radius, properly estimate hardness as well as corresponding Youngs modulus and concluding on structural properties of the micrometre-range ceramics fibres.

Preparation and properties of Ba1−xCaxTiO3 nanopowders obtained by mechanochemical synthesis

ABSTRACT The calcium-substituted barium titanate nanopowders Ba1−xCaxTiO3 (0.2 ≤ x ≤ 0.3) have been obtained at room temperature by mechanochemical synthesis. The formation of the perovskite phase was controlled by X-ray diffraction studies at various milling duration. The powders possess the perovskite crystallographic structure directly after milling longer than 10 h. The dielectric properties of the ceramics obtained by sintering of the nanopowders were investigated in the temperature range between 300 and 500 K. The temperature dependence of permittivity exhibited a single anomaly, which corresponds to the ferroelectric–paraelectric phase transition.