"One of the major drawbacks of modern alloyed metal cathodes Pd-Ba is the inhomogeneous distribution of the intermetallic Pd5Ba in the matrix Pd. This fact leads to an underestimation of life and technical performance of devices of microwave electronics on the basis of the cathodes. A substantial improvement in uniformity of cathode alloys Pd-Ba should lead the operation of mechanical activation of powder Pd, carried out prior to its compression process. The paper studied the effect of mechanical activation on the particle shape, particle size distribution and dispersion of powder Pd. It is shown that mechanical activation results in a substantial reduction in the average size and average particle size of Pd powder, as well as a substantial increase of the specific surface of the particles. The optimal regimes of mechanical activation of powder of Pd with a view to its use for metallosplavnyh cathodes."
Keywords: alloyed metal cathodes Pd-Ba, mechanical activation, dispersion, particle size distribution, average particle size, surface area, the emission properties
For the first time, using modern analytical methods studied phase and impurity composition of the cathode alloys Pd-Ba, obtained by industrial technology. The concentration of harmful impurities (C, Zn, Ba, Cu) in objects of study does not exceed the standards for these materials. Transmission electron microscopy and X-ray analysis confirmed the previously observed biphasic alloys Pd-Ba, from which one phase - intermetallic compound (Pd5Ba), second - palladium (matrix), wherein the intermetallic compound is very unevenly distributed in the matrix. The object of the study was first detected undesirable phase Pd2O. It is found that in the alloys of Pd-Ba grain Pd - large (about one micron), grain phase Pd5Ba - from a few hundred nanometers to one micron. All beans there is a high density of randomly distributed dislocations. Processing methods are proposed to improve the homogeneity of the alloy.
Keywords: alloyed metal cathodes, Pd-Ba, emission properties, transmission electron microscopy, X-ray analysis, impurity composition, the coefficient of secondary electron emission
For the first time, using modern analytical methods studied phase and impurity composition of the cathode alloys Pt-Ba, obtained by industrial technology. The concentration of harmful impurities (C, Zn, Ba, Cu) in objects of study does not exceed the standards for these materials. Transmission electron microscopy and X-ray analysis confirmed the previously observed biphasic alloys Pt-Ba, from which one phase - intermetallic compound (Pt5Ba), second - platinum (matrix), wherein the intermetallic compound is very unevenly distributed in the matrix. It is found that in the alloys of Pt-Ba Pt grains - small (a few hundred nm) and grain Pt5Ba - large (make several microns) and more sophisticated. Inside there are grains Pt5Ba voltage. Processing methods are proposed to improve the homogeneity of the alloy.
Keywords: alloyed metal cathodes, Pt-Ba, emission properties, transmission electron microscopy, X-ray analysis, impurity composition, the coefficient of secondary electron emission
The paper discussed the mechanism of formation of polycrystalline hexagonal barium ferrite. The influence of alloying elements on the location of Fe3 hexagonal block R, on the border of hexagonal and spinel blocks (RS). It is shown that the presence of weakly diamagnetic ions or dopants in these positions provides specific properties of hexagonal ferrites and their practical use.
Keywords: hexaferrite barium, dopant, magnetic properties, the mechanism of formation, anisotropy, polycrystalline, magnetization, Mossbauer spectroscopy, the coercive force, Curie temperature
Recently, BiFeO3 multiferroics have drawn a great deal of attention due to their superior ferroelectric properties in epitaxial thin film form in comparison to counterpart bulk single crystals or ceramics. In this work we present the results on magnetic properties of multiferroic ultrathin films (30-300 nm) of BiFeO3, (BiLa)FeO3 and (BiNd)FeO3 obtained by sputtering in transverse high frequency discharge, vacuum laser oblation and metalorganic chemical vapour deposition on monocrystalline substrates of (001) SrTiO3, (100) MgO and (100) Al2O3. The concentration of Bi, La и Nd in dodecahedral sublattices was varied. A novel effect of treatment of multiferroic films in a negative corona discharge has been investigated. It is demonstrated that the magnetisation may be increased by up to 35% whilst the change in is not noticeable. This effect does not depend on neither film composition no technological method.
Keywords: multiferroics, magneto-electric materials, methods of preparation, the films of bismuth ferrite, pseudomorphic structure, magnetic properties, corona discharge
The coloration centres (CC) in crystals of rear earth gallium garnets (REGG): Gd3Ga5O12 (GGG), Gd3Sc1,6Ga3,4O12 (GSGG) и Nd3Ga5O12 (NGG) obtained by Chohraljskiy method, were investigated by methods of optical spectroscopy and spectral analysis in the wavelength range of 0,2-0,87 microns. In the case of keeping the samples under dark conditions, unstable CC were formed in the crystals of GGG and GSGG. The absorption maxima are at λmax1 = 0,243 m and λmax2 = 0,275 m at concentration of N ~ 1018 cm-3. It is suggested that the observed enlightenment is caused by the recharging of growth defects and occurring the energy levels in the band gap of garnets. It appears that these CC correspond to centres of O- holes, originated from gallium vacancies V3-Ga 3+ in tetrahedral and octahedral nots which form near clusters of [V3-Ga 3+ - V2+O2- ]
Keywords: color centers, rare earth gallium garnets, kristylly, Czochralski method, the crystal lattice
To date, the main method of mass production of advanced functional materials for various purposes is the ceramic technology. In the manufacture of multi-component oxide compounds using of ceramic technology is difficult to achieve high uniformity of chemical composition. For activation of the raw ingredients and make it more uniform use of chemical-tions (co-precipitation of salts or hydroxides, spray drying, Cryochemistry) and physical-tions (mechano-chemical, microwave, ultrasonic) methods. The paper presents the results of work on obtaining Ni-Zn-ferrite 2000NN radiation-thermal sintering. The influence of base composition and alloying additions on the electromagnetic properties of the ferrites. Confirmed the effectiveness of the use of surface-active additives To increase the density of the raw pieces and level parameters. We propose a model that explain schaya efficiency of dopants in the radiation-thermal sintering.
Keywords: Nickel-zinc ferrite, radiation thermal sintering, base composition, alloying additives, permeability
Promising absorbing materials along with a Ni-Zn-ferrites are Mg-Zn-ferrites, as they are also intensively absorbs electromagnetic waves in the frequency range from 50 MHz to 1000 MHz. The main advantage of the Mg-Zn-ferrite is used as an inexpensive raw material magnesium oxide. The paper presents the results of research to improve the efficiency of broadband radio-magnesium-zinc ferrite by increasing the contribution of the dielectric loss. The influence of alloying elements of the atmosphere gas and cooling after the sintering thermal radiation by absorption of electromagnetic waves. Confirmed cooling efficiency of products after sintering in an atmosphere with reduced oxygen partial pressure to increase the dielectric constant. A model is proposed to explain the increase in the dielectric loss ferrite during cooling in a reducing atmosphere.
Keywords: radioabsorbing ferrites, microstructure grain boundaries radio measurement radiation thermal sintering
The spectra of thermally stimulated conduction currents (TSCC) in (TmBi)3(FeGa)5O12:Ca2+ ferrite-garnet films have been investigated with the purpose to reveal electrically active centres. The samples were fabricated by liquid phase epitaxy (LPE) from melt solution on the Gd3Ga5O12substrates with the crystallographic orientation (111) with the use of Bi-containing flux (without Pb). Increasing the concentration of Ca2+ions in the films were realised by increasing the concentration of CaO in the melt solution. The obtained films contained Ca2+ ions from 0,03 f.u to 0,1 f.u. With the help of standard thermoactivation current spectroscopy the spectra of the initial samples and samples subjected to ultraviolet radiation and negative corona discharge were obtained. The characteristic parameters of electrically active defects were calculated.
Keywords: thermally induced electrical current, ferrite garnet films, electrically active centres, deep-level capture, charge compensation, Ca- doping, ТСТП-spectra, temperature position