B. M. Rud

Production and Properties of Thick Magnetoresistive Films from Fine Ni3B Powders

Pastes and films are produced from Ni3B powders of different particle sizes using thick-film technology: screen printing of pastes on a dielectric substrate and subsequent heat treatment in air without any protection. The phase composition and structure of the films are examined by X-ray diffraction and electron microscopy; the size of nanostructured elements (ferromagnetic Ni and dielectric layer of B2O3) formed during heat treatment of the films is determined. The magnetoresistance of the films in a 0−2 T magnetic field is measured. The influence of the external magnetic field on the magnetoresistance of the films is determined by spin-dependent tunneling of charge carriers.

Effect of Electrode Material on the Electrical Properties of Tin Dioxide Thick Films

The influence of electrode materials made of Ag-containing paste and Ni3B-based paste on the properties of fine SnO2 thick films is studied. The Sn0.97Sb0.03O2 nanopowder is introduced into the thick-film composite to intensify film consolidation during heat treatment, enhance film adhesion to the substrate, and control the resistivity. X-ray diffraction and electron microscopy are applied. The dependences of film resistivity on composition of the conducting phase are established. The effect of heat treatment temperature on the resistivity and current-voltage characteristics of films on silver and nickel electrodes is examined. It is shown that the electrodes made of powdered Ni3B paste can be used for SnO2 films whose heat treatment temperature does not exceed 1073 K, in particular, for gas sensors.

Modification of the structure and properties of Ni3B-based thick films by the action of laser radiation

The results of studying the influence of pulse laser radiation on the surface morphology and certain electrophysical properties of Ni3B-based thick films produced by screen printing of composite pastes onto a dielectric substrate are presented in this work. The action of nanosecond pulses promotes the size reduction of the conducting phase particles, whereas, under microsecond pulses, the distribution of the conducting phase remains the same on the whole surface. The irradiation with millisecond pulses at energies of E = 0.4–0.6 J results in the surface flowing. The current-voltage characteristics and the dependence of the electrical resistivity on the temperature are presented. Laser processing of the samples in the nano- and microsecond ranges is established to promote the work of resistors, according to the standard and technical conditions, when the I-U linear dependence is realized.

Effect of Pulsed Laser Radiation on the Properties of Resistive Thick Films Based on Nickel and Barium Borides

We have used atomic force microscopy to study the surface morphology of resistive thick films based on powders of nickel and barium borides and a glass binder, treated with laser radiation. We used x-ray phase analysis to study the phase composition of these films. We have observed a change in the surface morphology, the phase composition, and the electrical resistance of the studied films as a function of the laser radiation energy.

Laser Treatment of Thick Films Based on Powder Composites of Nickel Boride

The thermophysical parameters (coefficients of thermal and temperature conductivity, coefficient of reflection of the laser beam) of resistive thick films (RTF) of powder composites based on Ni3B and glass were determined. Coefficients of thermal conductivity were calculated using the theory of general conductivity for a multicomponent system. The coefficient of diffuse reflection was calculated from the indicatrix of dispersion of the laser radiation. The parameters obtained were used to calculate the dependence of surface temperature of a thick film under the action of pulsed laser radiation on the duration and energy of the impulse and the radius of the laser spot.

Alternating-current conduction in thick refractory boride films

ConclusionsA study was made for the first time of the electrical resistance of thick barium, lanthanum, and nickel boride films in the frequency range 500 Hz–200 MHz. Up to 500 kHz the resistance of the films was independent of frequency. In the range 30–200 MHz the resistance of low-resistance films grew with frequency, and that of high-resistance films fell. Such behavior of films may be due to two mechanisms of electrical conduction — jump conduction over localized states in the vicinity of the Fermi level and metallic conduction — being superimposed on one another.

Conductive Composite Materials Based on Thermally Stable Fluorine-Containing Polyamide and Binary Filler

The feasibility of producing “binary filler + polymer matrix” conductive composite film is demonstrated. The mixture of nickel boride and carbon nanofiber at various ratios is chosen as the filler. The film microstructure is studied by SEM. The electrical–physical properties of the films (volt-amps diagrams and the R(T) dependence are determined). It is established that the thermal resistivity constant reverses sign, when the carbon nanofiber is introduced.

Effect Of Formation Conditions of Thick Granular Films Based on Dispersed Co 3 b On Their Phase Composition and Magnetoresistance

An important scientific and technical problem on developing thick resistive granular films used in microelectronics and tool manufacturing is solved. Magnetoresistive Co-containing granular films are obtained by screen printing the pastes consisting of fine-grained cobalt boride Co3B and organic binder on a dielectric substrate. Then, the deposited films are heat treated in air with no protection at all. Differential thermal analysis and thermogravimetric analysis reveal that only ferromagnetic Co (FCC) and amorphous B2O3 are present in the structure of the films at T = 650–850°C. On this basis, the modes for the heat treatment of films are developed. The effect of magnetic field on the electrical resistance of films is studied.

Conductive Film Materials Based on Thermally Stable Fluorine-Containing Polyamide and Nickel Boride

The development of resistor materials science and, namely, the feasibility of developing a composite film material based on the thermally stable polyamide and nickel boride as current-conducting filler, is considered. A process for producing films is developed: the films are obtained by coating the glass substrate with polymer solution with a pre-dispersed filler, followed by forming at 80°C with subsequent drying at 150°C until constant weight. The microstructure and topography of the film surface is studied by SEM and AFM. The formation of two-layer composite with the formation of conducting cluster (when the content of the conducting phase is >30 wt.%) from the substrate side is shown. Volt-amps diagrams are studied and analyzed by the differential method. The R(T) dependence is obtained and the temperature resistance coefficient is determined; the latter is positive and its value is 1.67 · 10–3 °C–1.

The Surface Morphology and Electrophysical Properties of Thick SnO2–Sb Films After Laser Processing

The influence of laser pulses on the structure and electrophysical properties of resistive thick films based on the Sn0.9Sb0.1O2 solid solution is studied. Scanning electron microscopy, atomic force microscopy, and X-ray diffraction are used to examine the structure of resistive thick films and determine the distribution of Sn0.9Sb0.1O2 solid solution in surface layers and across the film. Exposure of thick resistive films to nano- and microsecond laser pulses changes their currentvoltage characteristics compared to samples subjected to millisecond pulses. The current-voltage characteristics become practically linear in the range from 1 to 10–11 V, thus allowing one to determine the optimum (α = 1) operating voltage range for resistors. The temperature coefficient of resistance depends on the length and energy of pulses.