Zygmunt Surowiak

Properties of nanocrystalline ferroelectric PZT ceramics

Abstract Amorphous nanopowders of Pb(Zr0.5Ti0.5)O3 (PZT) solid solution were obtained by sol-gel processing. As-obtained nanopowders ( r ≈30×10−9 m) underwent consolidation by conventional ceramic sintering, hot pressing, and rapid thermal annealing. As result of such technological methods PZT ferroelectric ceramic samples were obtained. They exhibited lack of voids, density close to the theoretical X-ray density, homogeneity from both chemical and physical point of view and stoichiometric chemical composition. It was found that each ceramic sample was a conglomerate of grains exhibiting mean dimension r =0.3–3×10−6 m depending on sintering conditions. The nanocrystalline structure of the ceramics grains has been revealed. Dimension of the crystallites ( D =20–75×10−9 m) were found to depend on temperature (TS) and the rate of sintering (νT) of the amorphous nanopowders. Dielectric and piezoelectric properties of nanocrystalline PZT ceramics depended on both sol–gel processing conditions and sintering conditions.

The properties of the non-stoichiometric ceramics (1-x)PbMg1/3Nb2/3O3-(x)PbTiO3

Abstract (1− x )PbMg 1/3 Nb 2/3 O 3 –( x )PbTiO 3 i.e. (1− x )PMN–( x )PT ceramics with x ⩽0.15 have been obtained and investigated. With increasing x the temperature T m increases, at which dielectric permittivity reaches its maximum ( e m ), increases the value of e m and decreases the degree of the diffuse phase transition. For x ⩽0.075 dominates electrostrictive mechanism while for x >0.075 piezoelectric effect gives a contribution into electromechanical deformation of the samples. Special attention is paid to the problem of nonstoichiometry (excess and deficit of PbO and excess of MgO).

Synthesis and dielectric properties of Am-1Bi2BmO3m+3 ceramic ferroelectrics with m=1.5

Abstract Bismuth containing ceramic materials of molecular formula Bi 5 TiWNbO 15 , Bi 5 Ti 1/2 W 1/2 Nb 2 O 15 , Bi 5 Nb 3 O 15 have been synthesised and fabricated. The materials are known as the Aurivillius phases. The Aurivillius phases are a family of oxide ferroelectrics generally formulated as A m −1 Bi 2 B m O 3 m +3 . The process of preparation was investigated by X-ray diffraction method as well as the simultaneous thermal analysis, in which both thermal (DTA) and mass change effects (TG) were measured on the same sample. The synthesis of the Aurivillius phases was carried out according to the solid state reaction from the conventional mixture of oxides (Nb 2 O 5 , WO 3 , Bi 2 O 3 , and TiO 2 ). DTA and TG traces showing the synthesis effects have been recorded. Investigations of the crystalline structure, microstructure and basic dielectric properties were performed.

Piezoceramic Transducers with High Thermal Stability of the Resonance Frequency

Methods for increasing thermal stability of the resonance frequency f r of the PZT-based piezoceramic resonators are shown. An influence of ( x )PbTiO 3 content and an effect of doping ions on j f r / f r in the PZT solid solution has been considered. Correlation between qualities of the domain structure, spontaneous deformation parameters i T , i Re , degree of domain reorientation m , internal friction Q m m 1 and mechanical quality factor Q m , has been revealed. An impact of electronegativity of the doping ions on f r thermal stability have been cleared up. Ferroelectric hardness has also been considered. The piezoceramic band filters exhibiting j f r / f r <0.2% and Q m =3225 have been thus obtained.

Thermal dependence of pyroelectric parameters of PZT-based multi-component electroceramics

Abstract Five-component electroceramics based on solid solution PbTiO 3 –PbZrO 3 –PbNb 2/3 Zn 1/3 O 3 –PbSb 2/3 Mn 1/3 O 3 –PbNb 2/3 Mn 1/3 O 3 was studied. The chemical composition of the solid solution varied with PbTiO 3 content. Thus samples exhibiting rhombohedral crystalline structure, tetragonal structure, as well as samples exhibiting compositions from the morphotropic phase boundary region (MBR) were under investigation. Conventional mixed oxide method was used for the powder preparation. Hot pressing technique was employed for fabrication of ceramic pellets. To produce pyroelectric activity the samples underwent high voltage poling (HVP) or low voltage poling (LVP). Thermal stability of the pyroelectric coefficient was measured according to both quasi-static γ ST ( T ) and dynamic method γ D ( T ). The customised measuring system was developed. Dependence of the dielectric permittivity e 33 /e 0 of poled samples on temperature was also recorded. Results are reported and explanation of the observed temperature traces for γ ST ( T ), γ D ( T ), and e 33 /e 0 ( T ) is given taking into consideration the two different methods of poling the multi-component samples.

Electrostrictive properties of ceramics obtained on the basis of ferroelectrk relaxors

Abstract 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 σ r; (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.

Sol-Gel Transparent PLZT Ferroelectric Ceramics

Lead lanthanum zirconate titanate (known as PLZT) ceramic powders have been prepared by the modified sol – gel method, and underwent consolidation by the hot uniaxial pressing method. Application of such technique of preparation permitted to receive fine-grained transparent PLZT x/65/35 ceramics, with x = 8 -10 La at.%. The present publication gives a detailed account of the relationships between technology and physical properties of obtained materials. To analyze all ceramics SEM, EDS and mercury porosimetry were performed, and dielectric properties were studied too. Quite wide light transparency from the visible to nearinfrared range for PLZT ceramics was detected using optical absorption and infrared spectroscopy.

Phase transitions in PbTiO3 microcrystals of different size

PbTiO3 crystal is a model ferroelectric material exhibiting perovskite-type structure, high Curie temperature (Tc = 765 K), large spontaneous polarization (Ps=0.42 Cm-2) and electrical conductivity at Tc (σTc =0.1 Ω-1m-1). A method of preparation of PbTiO3 micro-crystals (size 1 - 50 μm) exhibiting isometric shapes and a method of segregating microcrystals into fractions within a narrow size range has been developed. The present work gives results of investigations on kinetics of the phase transition in micro-crystals exhibiting different dimensions. It has been found that P4mm ↔ Pm3m phase transition occurs in microcrystals in the presence of a single plane interface of {023}-type. During cooling of micro-crystals, the phase plane is followed by formation of the domain structure, which is a superposition of 180° dielectric domains and 90° domains (i.e. structural twins). The temperature hysteresis of position of the phase boundary is ΔTPT ≈ 7K. Such a situation occurs in case of micro-crystals with dimensions larger than critical size (rcr ≈ 20 μm). In case of r < rcr the plane phase boundary is followed by formation of 180° domains only; the structure of 90° do not longer form. The thermal hysteresis also occurs but its value is two times larger (ΔTPT ≈ 14 - 17 K).

Interaction between the domain walls and the structural defects in BaTiO3 crystals

Investigations of the domain structure and the defect structure of single crystals were carried out by optical and electron microscopy. Peculiarities and relationships between the defect structure and the domain structure were revealed. It has been found that dislocations in a form of tristetrahedron projections appear on the surface and thermal treatment increases density of such dislocations in the crystal. The complex domain structure consisting in: (1) regions exhibiting different domain structure features, (2) metastable 90° a -a -domains with the substructure of the backward domains; (3) dense a -c -domain series; and (4) blocks exhibiting preferred orientation of positive domain edges on the surface was found. It has been stated that crystals poled at room temperature exhibit different surface reliefs on the opposite etched surfaces. It has been found that the surface layer of BaTiO3 crystal often exhibits the domain structure, which differs from the structure inside the crystal. Most often the c -domain surface layer exists on crystals exhibiting both simple and complex domain structure. However, the domain structure inside the crystal has an effect on the character of distribution and orientation of 180°D domain walls in the surface layer. Contribution to better understanding of electrical properties of real BaTiO3 crystals was done.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Preparation, basic physical properties, and possibilities of application of PZT-based thin films

Ferroelectric, polycrystalline thin films based on PZT-type solid solution were fabricated by the RF sputtering method. The chemical composition of the thin films was Pb(Zr0.53Ti0.45W0.5Cd0.5O3) and it corresponded to the morphotropic region of the phase diagram of the PbZrO3-PbTiO3-PbW0.5Cd0.5O3 solid solution. Homogeneity check and investigations of the thin film chemical composition were performed by X-ray microprobe analysis. It has been found that the thin films exhibit high homogeneity of the chemical composition and stoichiometry close to that of the target. The processing conditions diagram has been defined, which ensures conservation of stoichiometry of the chemical composition of the thin films. Experiments have shown that according to the conditions of the RF sputtering not only the perovskite-type crystalline structures are formed but also the pyrochlore-type structure, mixture of the perovskite and pyrochlore-type phases or the amorphous phase. The diagram showing clearly separated regions of processing parameters conductive to formation of these phases was determined. Dielectric and piezoelectric parameters of the thin films were also studied. Great application potential of the PZT-based thin films has been considered and possibility to employ as-obtained PZT thin films as active elements of the piezoelectric sensors has been reported.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.