In the paper the multiferroic (ferroelectric-ferromagnetic) composites based on ferroelectromagnetic/ferroelectric (BaFe1/2Nb1/2O3 (BFN)) powder and ferrite powder (zinc-nickel ferrite) were obtained by two technological methods. In the composite samples the ratio of the ferroelectromagnetic/ferroelectric powder to the magnetic powder was equal to 90:10. The ceramic powders were synthesized by the classical technological method using powder calcination/solid state synthesis, while densification of the composite powders (sintering) was carried by two different methods: (i) Free Sintering method (FS), and (ii) Spark Plasma Sintering (SPS).
At the work, a comparison of measurement results for composite samples obtained by two sintering methods was made. The studies included the following analysis: DTA, XRD, SEM, DC electrical conductivity, electric permittivity and magnetic properties. The result of measurements presented in the work revealed that the ceramic composite obtained by two different technological sintering method (classical technology – Free Sintering method and Spark Plasma Sintering technique) can be promising lead-free materials for functional applications, for example in sensors for magnetic and electric field.
A number of micromechanical investigations have been performed to predict behaviour of composite interfaces, showing that the detailed behaviour of the material at these interfaces frequently dominates the behaviour of the composite as a whole. The interfacial interaction is an extremely complex process due to continuous evolution of interfacial zones during deformation and this is particularly true for carbon nanotubes since the interfacial interaction is confined to the discrete molecular level. The atomic strain concept based upon Voronoi tessellation allows analyzing the molecular structure atom by atom, which may give a unique insight into deformation phenomena operative at molecular level such as interface behaviour in nanocomposites.
The aim of the study was to investigate the effect of soybean lecithin as a substitute for egg yolk in milk and tris based extenders in ram semen cryopreservation. Twenty ejaculates were col- lected from four healthy, mature Wrzosówka rams (2-3 years of age). Each ejaculate was divided into four equal aliquots and diluted with four different extenders: 1) milk extender containing 5% egg yolk, 2) milk extender containing 1.5% soybean lecithin, 3) tris extender containing 20% egg yolk, 4) tris extender containing 1.5% soybean lecithin. Extended semen was loaded into 0.25 ml French straws, cooled and frozen in liquid nitrogen vapor. Total motility, curvilinear velocity, plasma membrane integrity and fertilizing ability of sperm were assessed after thawing. Total mo- tility was lower (p<0.05) in tris-soybean lecithin extender when compared to other extenders. Curvilinear velocity was higher (p<0.05) for spermatozoa cryopreserved in milk-soybean lecithin extender compared to other extenders tested. For the percentage of live sperm no significant difference was observed between extenders. The lambing rate were higher (not statistically signifi- cant) in ewes inseminated with semen doses frozen in milk-soybean lecithin extender (42.9%) than in the tris-egg yolk extender (16.7%). In conclusion, replacing the egg yolk with soybean lecithin was effective in milk but not in tris extender.
The five-layer Aurivillius type structures with the general chemical formula Bi5Fe2-xMnxTi3O18, where x = 0, 0.6, 1.2 have been synthesized and tested. The SEM studies showed a significant increase in grain size in the manganese-modified Aurivillius type ceramic material (for x = 1.2). The increase in the amount of manganese ions (Mn3+) affects the decrease in the temperature at which the relaxation processes take place. Namely from 525 K (1 kHz) and 725 K (1 MHz) for BFT sample (x = 0) to 355 K (1 kHz) and 565 K (1 MHz) for BFM12T sample (x = 1.2). Using the Arrhenius’s law and the Vogel-Fulcher’s relationship the activation energy (Ea) and the relaxation time have been calculated. The value of Ea increases with the increase of the Mn amount from 0.737 eV (for x = 0) to 0.915 eV (for x = 1.2).
The paper presents the technology and basic properties of three compositions of lead-free ceramics: (i) (K0.44Na0.52Li0.04)NbO3, (ii) (K0.44Na0.52Li0.04)NbO3+0.5%mol Nd2O3 and (iii) (K0.44Na0.52Li0.04)NbO3+0.5%mol Pr2O3. Powders of the designed compositions based on KNLN were obtained with the classic ceramic technology, as a result of solid phase synthesis, from a mixture of simple oxides and carbonates. The synthesis of ceramic powders was carried out at Ts = 900°C for ts = 4 h, while compaction by free sintering at Tsint = 1100°C for tsint = 2 h.
XRD studies have shown that doping with praseodymium and neodymium promotes the formation of the tetragonal phase in the base composition (K0.44Na0.52Li0.04)NbO3 at lower temperatures. On the other hand, microstructural tests have shown that the admixture of neodymium and praseodymium improves the sinterability of ceramic samples during the technological process; however, the ceramic samples still exhibit high porosity.
The work three ceramic compositions based on PbZr0.49Ti0.51O3 doped with manganese (Mn), antimony (Sb), lanthanum (La) and tungsten (W) were obtained. The introduction of a set of admixtures was aimed at improving the sinterability of ceramic materials and optimizing its electrophysical parameters. Multi-component materials of the PZT-type with a general formula: Pb(Zr0.49Ti0.51)0.94Mn0.021Sb0.016LayWzO3 (where y from 0.008 to 0.012 and z from 0.012 to 0.014) were prepared by the conventional mixed oxide method. After mixing and drying the powder mixtures were calcined in air at 850°C for 4 h, while densification of the powders was carried out by the free sintering method at 1150°C for 2 h. The final steps of technology were grinding, polishing, annealing and putting silver paste electrodes onto both surfaces of the samples for electrical testing.
XRD, SEM, EDS, dielectric, ferroelectric, piezoelectric properties and DC electrical conductivity of the obtained ceramic compositions were carried out. X-ray tests of the crystal structure conducted at room temperature have shown that all obtained the PZT-type materials were a single phase (perovskite type) without the presence of a foreign phase. Symmetry of the crystal lattice was identified as space group P4mm. Temperature dielectric studies have shown high values of dielectric permittivity and low dielectric loss. The presented physical properties of ceramic samples based on PZT confirm their predisposition for application in modern microelectronic and micromechatronic applications.
The paper presents the results of research on the influence of sintering temperature on microstructure, DC electrical conductivity, dielectric, ferroelectric and magnetic properties of PbFe1/2Nb1/2O3 ceramics doped by Li in the amount of 5.0% wt., in the abbreviation PLiFN. The ceramic samples of the PLiFN material were obtained by the two-stage synthesis – columbite method and sintered by free sintering methods. Introduction to the basic PbFe1/2Nb1/2O3 composition of the lithium admixture to decrease the electrical conductivity and reduction of dielectric loss. The tests have shown that the increase in sintering temperature orders the PLiFN ceramic microstructure, which has a positive effect on its electrophysical properties. At room temperature, the PLiFN ceramic samples show both ferroelectric and ferromagnetic properties. Considering the functional parameters of the obtained ceramic samples, the optimal technological conditions are 1100°C/2 h.
We present the results of investigations of Pb(Fe1/2Nb1/2)O3 (PFN) ceramic samples obtained using two-step synthesis (i.e. columbite method). For obtained samples complex investigations of microstructure, magnetic and electrophysical properties have been performed at low and at high temperatures. Microstructure is characterized by small grains with high homogeneity and high density (low porosity). Impedance of samples and the phase shift angle have been measured using LCR Meter. Next the AC electric conductivity, dielectric permittivity and loss tangent have been calculated. AC conductivity at frequency 3 Hz was measured in similar way using Quantum Design PPMS System in magnetic fields 1000 Oe and 10000 Oe. At temperature range 240K-260K the anomalies of conductivity are observed. These anomalies depend on measuring cycle (heating, cooling) and magnetic field.