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A multicomponent lead zirconate titanate (PZT)-type ceramics doped with Mn4+, Sb3+, W6+, and Ni2+ with a perovskite structure was obtained. The designed material had a chemical composition of Pb(Zr0.49Ti0.51)0.94Mn0.014Sb0.02W0.014Ni0.02O3. Ceramic powders were synthesized by the calcination method, and they were densified by the free sintering method. We present the results of electrophysical measurements of the PZT-type ceramics, including scanning electron microscopy microstructure, dielectric, ferroelectric, pyroelectric, and thermally stimulated depolarization currents, piezoelectric properties and DC electrical conductivity. The results obtained for the multicomponent ceramics predispose it to micromechatronic applications as part of actuators.

Modern electronics expect functional materials that are eco-friendly and are obtained with lower energy consumption technological processes. The multiferroic lead-free BaFe1/2Nb1/2O3 (BFN) ceramic powder has been prepared by mechanochemical synthesis from simple oxides at room temperature. The development of the synthesis has been monitored by XRD and SEM investigations, after different milling periods. The obtained powders contain large agglomerates built by crystals with an estimated size about 12–20 nm depending on the period of milling. From this powder, the multiferroic BFN ceramic samples have been prepared by uniaxial pressing and subsequent sintering pressureless method. The morphology of the BFN ceramic samples strongly depends on high-energy milling duration. The properties of the ceramic samples have been investigated by dielectric spectroscopy, in broad temperature and frequency ranges. The high-energy milling of the powders has strongly affected the dielectric permittivity and dielectric loss of the BaFe1/2Nb1/2O3 ceramic samples. The usage of the mechanochemical synthesis to obtain the multiferroic lead-free BFN materials reduces the required thermal treatment and simultaneously improves the parameters of the BFN ceramics.

Effects of La3+admixture in barium lanthanum titanate (BLT) ceramics system with colossal permittivity on performance of prospective piezoelectric cold plasma application were studied. Usage of cold atmospheric pressure plasma appears promising in terms of industrial and healthcare applications. Performed investigation provide consistent evaluation of doping lanthanum amount on piezoelectric coefficients values with simultaneous capability of charge accumulation for effective plasma generation. Modification of ferroelectric materials with heterovalent ions, however with the lower radii than the original atoms, significantly affects their domain mobility and consequently electromechanical properties. To determine the piezoelectric coefficients, the resonance-antiresonance method was implemented, and values of piezoelectric and dielectric parameters were recorded. Finally the results indicated that addition of 0.4 mol.% of La3+ions to the ceramic structure maximally increased the values of piezoelectric coefficient tod33= 20 pC/N and to huge dielectric constant toε33T= 29277.

This paper describes the properties of a lead-free ceramic material based on barium titanate, designed for the construction of ultracapacitors and sensors used in mechatronic systems. The admixture of lanthanum (La3+) served as a modifier. The ceramic powders were obtained by the solid phase reaction method (conventional method&mdash, mixed oxides method&mdash, MOM). Technological conditions of the synthesis process were determined on the basis of thermal analysis. The obtained samples are characterized, at room temperature (Tr &lt, TC), by a single-phase tetragonal structure and a P4mm space group. Properly developed large grains (d = 5 &micro, m) contributed to the increase in electric permittivity, the maximum value of which is at the level of &epsilon, m &asymp, 112,000, as well as to a strong decrease in specific resistance in the ferroelectric phase, whereas above the Curie temperature, by creating a potential barrier at their boundaries, there was a a rapid increase in resistivity. The temperature coefficient of resistance of the obtained posistor is 10.53%/K. The electrical properties of the obtained ceramics were examined using impedance spectroscopy. In order to analyze the obtained results, a method of comparing the behavior of the real object and its replacement system in a specific frequency region was used, whereas the Kramer&ndash, Kroning (K&ndash, K) test was used to determine the consistency of the measured data. The proper selection of the stoichiometry and synthesis conditions resulted in the creation of an appropriate concentration of donor levels and oxygen gaps, which in turn resulted in a significant increase in the value of electrical permittivity, with small values of the angle of dielectric loss tangent. This fact predisposes the discussed material for certain applications (in the construction of ultracapacitors, among others).

Alkaline based materials have been considered as a replacement for environmentally harmful Pb(Zr,Ti)O3 (PZT) electro-ceramics. In this paper, the K1/2Na1/2NbO3 (KNN) ceramics were prepared in a three stage process: first Nb2O5, Na2CO3, and K2CO3 were milled in a high energy mill (shaker type) for different periods, between 25 h and 100 h, consecutively a solid state reaction was carried out at 550 &deg, C. Finally, the uniaxially pressed samples were sintered at 1000 &deg, C. The reaction temperature is lower for mechanically activated powders than in the case of the conventional solid-state method. The ceramic samples, prepared from the mechanically activated powders, were investigated by dielectric spectroscopy. The influence of the duration of the mechanical activation on the properties of the ceramic materials, e.g., ceramic microstructures, phase transition temperatures, character of the temperature dependences of dielectric permittivity, are discussed.

Electrocaloric (EC) structures for a new generation of cooling or heating elements utilize the temperature dependence of spontaneous polarization in some ferroelectric materials to convert waste heat into electricity and vice versa. A (Pb0.93La0.07) (Zr0.65Ti0.35)O3 material, have the largest recorded pyroelectric coefficient. An effective predicted form for such applications is fiber, due to small heat capacitance and quick response time, even for nano second laser excitation. Consequently, the presented work provides a description of the optimization of structural, ferroelectric and piezoelectric properties of obtained fibers, finally concluding on necessity of sintering temperature reduction in 100°C in contrast to bulk form to effectively prevent its destruction.

The lanthanum barium titanate (BLT) ceramics with the ABO3 perovskite-type structure has been investigated, and the optimum technology for preparation of BLT ceramics exhibiting high density and high dielectric constant has been developed. By means of conventional technology and sol-gel method ferroelectric ceramic Ba1-xLaxTi1-x/4O3, for x = 0.005, was obtained. After a solid-phase synthesis, the obtained powders were sintered using one of three ways: free sintering, hot pressing followed by free sintering, and free sintering followed by hot pressing. The ceramic samples were characterized in terms of their microstructure and dielectric properties.

In the work, the multicomponent Pb0.75Ba0.25(Zr0.65Ti0.35)1-aSnaO3 (PBZT/Sn) ceramics were obtained with various tin amounts (a from the range of 0.0 to 0.1). The densification of the PBZT/Sn ceramic samples was performed using pressureless sintering method. The effect of SnO2 content on the crystal structure of PBZT/Sn ceramics, microstructure, DC electrical conductivity and electrophysical properties (including dielectric and ferroelectric testes), were investigated. The PBZT/Sn ceramic samples exhibit high values of dielectric permittivity at the temperature of ferro-paraelectric phase transition and show the relaxor character of phase transition. Excessive SnO2 contents doping of the PBZT/Sn materials (already for a = 0.1) might lead to lattice stress and structure defects, which successively leads to the deterioration of ferroelectric and dielectric properties of the ceramic samples. The presented research shows that the addition of SnO2 to the base PBZT compound (in the proper proportion) gives an additional possibility of influencing the parameters essential for practical applications, from the areas of micromechatronics and microelectronics.

The main motivation of present article is to clarify the role of calcium ions in the formation of the mechanical properties of (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 ceramics. For this purpose the base ceramics as well as ceramics contain 0.5; 1; 2; 3; 4 at.% of calcium were prepared using conventional mixed oxide method. In the experiment, the nanoindentation techniques were applied to evaluate the elastic modulus and hardness values as a function of indentation depth. The results were compared with these in macroscale obtained by ultrasound techniques and shown that not always expensive nanoscale characterisation methods reveal real materials properties in microscale.

Relaxor ferroelectrics or relaxors are a class of disordered single crystals and ceramic materials, of peculiar structure as well as properties. The commonly known examples of such materials are Pb(Mg,Nb)O3 (PMN) ceramics as well as single crystals. The second most extensively studied relaxor ceramics is lanthanum-doped lead zirconate–titanate, described as x/65/35 PLZT when lanthanum content is x = 6–10 at%. Throughout the last few decades, there has been an increasing interest in rare-earth-doped PLZT ceramics, because PLZT can be easily substituted with lanthanide elements for La3+ ions. For this reason, the present studies concern the changes in microstructure and crystal structure as well as in dielectric properties, caused by modification of 8/65/35 PLZT with neodymium dopant. Modification of this material with Nd3+ influences the microstructure, electrooptical and dielectric properties, whereas the changes in crystal structure are slight. It was also observed that the maximum value of dielectric pr...

The solid solutions of PbZr1-xTixO3 (PZT) are the most known and widely applicable piezoelectric ceramic materials. The influence of different dopants on PZT properties has been studied for many years. Some of such compositions have revealed a behavior typical for ferroelectric relaxors. In the case of Pb0.75Ba0.25Zr0.70Ti0.30O3 ceramics (abbreviation PBZT 25/70/30), prepared by mixed-oxide processing technique elastic, it was found that macroscopic piezoelectric activity is present far above the temperature at which structural changes and maximum of permittivity occur in unpoled samples (~ 200 °C). Anomalies of the elastic and piezoelectric properties have been observed very clearly near the temperature of 152 °C. Within the temperature range of 152–220 °C, unstable piezoelectric properties have been detected due to the existence of polar micro/nano-clusters and non-trivial elastic-electric interactions between them, through the non-polar paraelectric matrix. The origin of such interactions could be lattice instabilities, dynamic change in polar cluster sizes, and fluctuations in chemical composition. Based on the results of the research, it can be said that PZT ceramics of such composition is a relaxor-like material and it is not a ferroelectric relaxor.

Barium bismuth niobiate (BaBi2Nb2O9) ceramics modified by calcium were prepared by solid state synthesis and two-step sintering process. An impact of calcium substitution on the A site of perovskite block is presented. The investigations are focused on dielectric as well as electric aspects of the modification. The presented results reveal that the concentration of a space charge is not preserved, what is surprising due to the homovalent nature of the dopant and no reason for creating additional lattice defects and charges connected. However, not only the valence of ions, but also the calcium-oxygen and barium-oxygen bond strength should be taken into consideration. Since the calcium-oxygen bond is probably weaker the loss of the bismuth oxide is expected to increase with an increase in the calcium content. Such a scenario results in appearance of a large number of negative charge carriers connected with unsaturated oxygen ions.

Recently worldwide environmental considerations demand the elimination of lead-based materials from all consumer items. Potassium sodium niobate solid solution seems to be one of the most promising candidate to replace the PZT-based ceramics in piezoelectric devices. In this paper the K1/2Na1/2NbO3 ceramics have been obtained from mechanochemically activated powders containing the stoichiometric ratio of niobium oxide, potassium and sodium carbonates. The activation process occurred in a high energy mill (shaker type), for different periods between 25 h and 100 h. The sintered ceramic samples, prepared from mechanochemically activated powders, have been investigated by XRD, SEM and impedance studies in order to determine the influence of mechanochemical process on the final ceramic properties. The ceramic properties have showed a strong correlation with the milling duration. Based on the performed investigations it is possible to distinguish between the material response related to the grains and the grain boundaries. The resistance of grains and grain boundaries increases with the high energy milling time. The similar trend has been recorded in case of capacitance. Moreover, the anomaly, related to the ferroelectric-paraelectric phase transition, is visible on both temperature dependencies of grains and grain boundaries capacitances.

In the present study two-phase BiNbO4//PVDF composites with 0-3 connectivity were studied by impedance spectroscopy within the frequency range Δν=100Hz-1MHz at room temperature. Polyvinylidene fluoride (PVDF) acted as a matrix whereas bismuth niobate (BiNbO4) powder acted as a dispersed phase. The volume fraction of the ceramic phase was cV=2, 4, 6, 8, 10, 16 and 20vol%. Analysis of the impedance data registered for composites as well as for BiNbO4 ceramics and PVDF polymer was performed on the base of complex dielectric permittivity mathematical formalism. It was found by impedance spectroscopy that concentration of the dispersed phase had an effect on dielectric properties of ceramic-polymer composite. Experimental data of impedance spectroscopy were fitted to the corresponding equivalent circuit using the complex non-linear least squares method. An equivalent electric circuit consisting of a series combination of two parallel combinations of a resistance R and a constant phase element CPE was found to describe well the dynamic dielectric response of the objects under study. Parameters of the equivalent electric circuit were calculated and it was found that two distinct relaxation processes were present in the composite samples. It was also found that volume fraction of the dispersed phase cV=8vol% corresponded to a local minimum of resistance whereas cV=10vol% of the dispersed phase corresponded to a local minimum of capacitance.

Goal of the present research was to investigate the influence of V2O5 additive on the structure and dielectric properties of BiNbO4 ceramics. To fabricate BiNbO4 ceramics with V2O5 added the solid state reaction route and pressureless sintering was utilized. Thus obtained ceramics was characterized in terms of its microstructure (SEM), chemical composition (EDS), phase composition and crystalline structure (X-ray phase and structural analysis, respectively). Also dielectric properties in both temperature and frequency domains were investigated. The impedance spectroscopy was utilized for dielectric characterization and the measurements of complex impedance were performed within the frequency range ν =10Hz-1MHz and temperature range T =RT-550°C. It was found that V2O5 additive changed slightly lattice parameters of BiNbO4 ceramics, decreased porosity of samples and revealled relaxation phenomena within the frequency ranges ν =102-103 Hz and ν =105-106 Hz at temperature T>285°C.

Compactness and large energy conversion capacity are the main reasons of development of sophisticated ceramics materials in microfibers form, which are prepared for high-speed multiferroic systems and devices. These multifunctional composite applications are owing to coupling of electrical and magnetic properties, as well as additional thermal and mechanical properties. So that, they are suitable for magnetic sensors, electrically tunable non-linear transducers, and non-volatile memories. In our experiment, the thin fibers ceramics have been produced using special environmental chamber where the high temperature sintering can be protected by controlling such parameters as temperature and sintering atmosphere. Consequently, for these purposes structural and physical properties, preparation and thermal synthesis of micrometer sized lead lanthanum zirconate titanate (PLZT) fibers were investigated thoroughly. Since the phase transition properties of PLZT fibers differ much, the production process of fibers s...

The effect of thermal treatment on the properties of Bi-layered ceramics, and particularly of the BaBi2Nb2O9 ceramics was considered to be marginal, despite the fact that their dielectric and relaxor properties are strongly related to the degree of heterogeneity. The aim of this article is to determine the influence of defects, especially the concentration of oxygen vacancies, on the relaxor properties of BaBi2Nb2O9. The results show that the oxygenation, taking place in the first phase of post-sintering annealing, do not affect significantly the values of the parameters characteristic of ferroelectric relaxors. The parameters undergo changes only after prolonged annealing, when the content of barium and bismuth were slightly changed.

The mechanical properties of the pure as well as vanadium modified BaBi2Nb2O9 ceramics have been studied in macro and nano-scales using three different methods. Specifically for macro-scale, ultrasonic velocity and internal friction were employed to evaluate the Young modulus (E), whereas for nano-scale the nanoindentation method was a very useful tool to obtain the elastic modulus and hardness. These results reveal the strong influence of vanadium admixture on mechanical properties of the discussed material. In the case of modified ceramics the value of Young modulus increases, which is probably connected with the decreasing of the number of defects. Moreover, the described results show the significant differences in mechanical properties measured on nano and macro-scale. It is concluded that the knowledge of the mechanical properties of the ceramic material is complete only when we take into account both the macro and nano-scale.

Effect of Sr content in lead zirconate titanate PZT ceramic system on performance of piezoelectric transformer application were studied. Our experiments provide consistent evaluation of doping strontium amount on piezoelctric coefficients values and final voltage gain and efficiency of piezoelectric transformer. Extreme values of these parameters are preferred for MEMS device effective driving. Modification of ferroelectric materials with isovalent ions, however with the bigger radii than the original atoms, significantly affects their properties. Particularly the electromechanical coefficients of (Pb1-xSrx)(Zr0,70Ti0,30)O3, for mole %’s as x = 0.05, 0.10 and 0.15 ceramics exhibit marked increase, if the PSZT material stoichiometry is near the ferroelectric/relaxor phase boundary. To determine the piezoelectric coefficients, the resonance-antiresonance method was implemented. The results indicated that addition of Sr2+ ions in the amount of 5 mol% in the ceramic structure maximally increased the values of piezoelectric parameter to d31 = 8.2 pC/N and mechanical quality factor Qm = 2902. Finally we demonstrated that in spite of the high piezoelectric coefficients for certain material only the practical examination must be applied in order to draw decisive application conclusions due to the complexity of the double energy conversion in such a specific device as the piezoelectric transformer.

Ferroelectric materials systematically enter into the structure of microelectronic devices. The ability to increase the packing density of the ferroelectric structures, and thus the piezoelectric coefficients of the final device, is primarily limited by the fact that such tiny ferroelectric structures may not preserve their microscopic properties at macroscopic scale. A problem of current interest in ferroelectric research is to get to know how to modify the domain structure and the piezoelectric properties of the material, if the polycrystalline material consists of grains and grain boundaries, in which electrical properties differ significantly. In this paper, we have combined the Impedance Spectroscopy (IS), as a method for detecting such inequality in the form of separated impedances, and Atomic Force Microscopy (AFM), as techniques for direct local engineering and investigation of grain and grain boundaries conductivity. We would like to present hitherto unreported connection between values of electrical parameters obtained by both methods.

Piezoelectric transformers (PT's) based on thin ceramics disc with the double “ring-dot” electrode design are studied on the domain engineered ceramics disc. Various possibilities of the domain volume distributions are experimentally prepared and the problems of non-homogeneous poling are discussed. Parameters of PT's such as transformation ratio and efficiency are measured as a function of frequency, resistive load and electrode geometry. The best transformation ratio and efficiency parameters were found for the homogeneously poled PT samples. Domain engineered poling direction distribution with alternating oppositely poled segments are the best among the non-homogeneously poled PT's, although the parameters are not better than for the homogeneously poled PT's.

BBN (BaBi 2 Nb 2 O 9 ) is very interesting and promising lead free material with relaxor properties in capacitors, sensors and actuators. Results of investigations of fine-grained, weakly porous, BBN-type ceramics using hot-pressing method are presented. Based on a thermal deformation curve (i.e. a shrinkage curve) of a sample the method for optimisation of the hot-pressing sintering conditions has been proposed. Some advantages of hot-pressing method over the classical ceramic method used for BBN ceramics fabrication is shown. It has been found that the deficiency in bismuth causes a change of the space group of the perovskite phase crystalline structure of BBN and unit cell parameters. The influence of bismuth deficiency on dielectric properties materials and relaxor features is presented. The measurements of pyroelectric and thermally stimulated depolarization currents (TSDC) were carried out in order to better display unusual behaviour of dielectric characteristics.

The (Ba x La1−x )Ti1−x/4O3 (BLT, 0.001 ≤ x ≤ 0.005) amorphous gel was prepared by sol-gel process. The electrical properties of obtained materials has been investigated by impedance spectroscopy. Detailed analysis of impedance spectra allowed to propose an adequate equivalent circuit, which described the electric properties of discussed materials very well. Basing on the obtained circuits and the fitting procedure the grain and grain boundary resistivity was determined as a function of temperature and La concentration. With increase of La admixture the contribution of grain and grains impedance to the bulk impedance changes. It was found that the small amount of La additive decreases the blocking factor of the grain boundary in the temperature range 600–850 K, whereas the amount of La on the level of 0.4–0.5 mol.% causes the sharp increase of the mentioned factor. The fact may be attributed to a decrease of grain activation energy and increase of the grain boundary one.

The subject of the paper is lead free bismuth layer structure oxides (1-x)Bi3TiNbO9-xBaBi2Nb2O9 (x=0; 1; 2; 3 mol). The influence of Bi3TiNbO9/BaBi2Nb2O9 ratio on dielectric and structural properties was studied in a wide range of temperatures. Change in the ratio causes a decrease in the maximum value of dielectric permittivity and shifts the temperature of ε’max to low values, leading to linear decreasing of average grain size and linear increasing of ceramics density. These results indicate an augment of the packing degree and the participation of pores are significantly decreased with the increase of BaBi2Nb2O9 compound intake. Moreover, for 0.7Bi3TiNbO9-0.3BaBi2Nb2O9 ceramics the dielectric phase transition is broadened and the properties characteristic for the ferroelectric relaxor appear.

In the paper the influence of mechanical activation of the powder on the final dielectric properties lead-free Ba(Fe1/2Nb1/2)O3 (BFN) ceramic was examined. The BFN ceramics were obtained by 3-steps route. Firstly, the substrates were pre-homogenized in a planetary ball mill. Than, the powder was activated in vibratory mill (the shaker type SPEX 8000 Mixer Mill) for different duration between 25 h and 100 h. The influence of the milling time on the BFN powder was monitored by X-ray diffraction. The diffraction data confirmed that the milling process of the starting components is accompanied by partial synthesis of the BFN materials. The longer of the high-energy milling duration the powders results in increasing the amount of amorphous/nanocrystalline content. The mechanically activated materials were sintered in order to obtain the ceramic samples. During this temperature treatment the final crystallisation of the powder appeared what was confirmed by XRD studies. The performed dielectric measurements have revealed the reduction of the dielectric loss of the BFN ceramics compared to materials obtained by classic methods.

In this paper the multicomponent PZT-type solid solution doped by barium, calcium, strontium, bismuth and germanium with composition: Pb0.975Ba0.01Ca0.01Sr0.005(Zr0.52Ti0.48)O3 + 1.4 wt.% Bi2O3 + 0.3 wt.% GeO obtained by hot uniaxial pressing method is described. The results of structural, dielectric, ferroelectric and electromechanical studies of these ceramics are presented. It has been stated that introduction to the basic composition PZT admixtures of the barium, calcium, strontium, bismuth and germanium has a positive effect on the electro-physic parameters of obtained ceramic samples. This material has good microstructure, with high value of the dielectric permittivity (with the high temperature of phase transition) as well as low dielectric losses. It allows considering this material as elements for low frequency and high temperature electromechanical transducers.

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 Burn's temperature have changed. These results indicate that the behaviour of the relaxor ferroelectrics is weakened by the increase in the grain size.

In the hereby paper the implications of thermal modification of BaBi2Nb2O9 ceramics in high vacuum (5×10−11 bar) at a temperature equal of 1173K are widely discussed. The mentioned modification caused changes in the ions concentration (confirmed by EDS and XPS analysis) and as a consequence an influence on the value of the unit cell parameters as well as on the dielectric and relaxor properties of described ceramics. The obtained results of EDS and XPS analysis of the sample before and after thermal treatment revealed bismuth ions diffusion to the surface of the sample (which was expected) and an almost complete the lack of barium ions on the modified surface. The comparison of EDS and XPS analysis results, suggested that they penetrated the interior of the sample and embedded into the crystal structure in place of bismuth. The hypothesis is in good agreement with the results of X-ray diffraction – the volume of the unit cell had an insignificant increase. The changes in the ions concentration influenced, also in a distinct manner, the dielectric and relaxor properties as well as on the shape of temperature characteristic of thermal stimulated depolarization current observed in BBN ceramics.

The research presented in this paper concerns BaBi2Nb2O9 (BBN) which is the member of the Aurivillius family and seems to be interesting from the point of view of its potential applications in storage media. Our investigations focused on temperature dependence crystal structure and mechanical properties of this ceramics as well as on the dielectric properties of samples. Correlation between positions of the maximum of the real part of electric permittivity and the behavior integral width of diffraction lines XRD versus temperature had been discussed based of the presence of polar nano-regions with orthorhombic distortion in macroscopic tetragonal matrix.

In this paper BST//PVDF composites with 0-3 connectivity were prepared from (Ba0:6Sr0:4)O3 (BST60/40) ceramic powder and polyvinylidene fluoride (PVDF) powder by a hot pressing method, for different concentration of the ceramic phase (cV ). Morphology of BST//PVDF composites was observed by transmission electron microscopy and scanning electron microscopy, whereas the crystalline structure was studied by the X-ray diffraction method. The temperature dependence of dielectric permittivity of BST//PVDF composites was measured in the frequency range of f =10kHz-1MHz. The split-post dielectric resonator (SPDR) was used for the measurements of the real and imaginary part of dielectric permittivity of BST//PVDF composites in the microwave frequency range of f =3-10GHz. It was found, that the dielectric properties of the ceramic-polymer composite for cV >20% change significantly for both small ( f =10kHz-1MHz) and high ( f =3-10GHz) frequencies. The abrupt increase in permittivity may indicate an excess of the percolation threshold, so the ceramic-polymer composite for the concentrations of the active ceramic phase cV >20% cannot be indexed as composites with 0-3 connectivity.

In this paper the BiFeO3//Bi4Ti3O12 (BF//BiT) ceramic-ceramic composites with 0-3 connectivity were prepared from BiFeO3 and Bi4Ti3O12 ceramic powders by free sintering method at T=900 C, for different concentration of the BF ceramic phases. Bi4Ti3O12 and BiFeO3 ceramic powders were synthesized by the conventional mixed oxide method (MOM). Synthesized BF powder was dispersed in a BiT solution and next such composite was pressing and sintering. Crystalline structure was studied by X-ray diffraction method. The dielectric properties of the BF//BiT ceramic composites were also investigated. Temperature dependence of dielectric permittivity of BF//BiT composites was measured in the frequency range of f =10kHz-100kHz. It was found, that properties of the ceramic-ceramic composite are not a simple sum of properties of the phases constituting the composite but they depend on both the way of connectivity and mutual influence of the phases on each other. The abrupt increase in permittivity may indicate an excess of the percolation threshold, so the ceramic composite for the concentrations of the BF ceramic phase cV >10% cannot be indexed as composites with 0-3 connectivity.