Thermal expansion of semiconductor materials

The thermal expansion of tellurides of germanium, bismuth, and intermetallic compounds is investigated over the temperature range 293-973 K.Belarusian Agricultural Technical University, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 5, pp. 612–616, May 1994.     

High-field galvanomagnetic properties of compensated metals under electron-surface and intersheet electron-phonon scattering (tungsten)

The field and temperature dependence of the transverse magnetoresistivity and the Hall coefficient for single-crystal tungsten with a resistivity ratio _293K/_4.2K varying from 780 to 80800 are measured at temperatures between 4.2 K and 50 K in magnetic fields up to 150 kOe. The role of the static skin effect and the temperature breakdown in the galvanomagnetic properties of the compensated metals is evaluated through experiments with tungsten. The experimental data shows that the galvanomagnetic properties of the compensated metals in the high magnetic fields are not dependent only on the Fermi surface geometry. A substantial role in their formation is played by the processes of the electron-surface and the intersheet electron-phonon scatterings.     

Investigation of Acoustic Emission in Low-Carbon Steels during Development of Fatigue Cracks

AE control results for cyclic tests of metal samples with a notch are presented. The main stages of the fatigue crack development and standard AE parameters are matched. A criterial plane which allows to separate clusters corresponding to the stages of stable and avalanche-like defect growth has been constructed. It is shown that the boundaries of clusters remain unchanged irrespectively to the differences in the kinetics of damage development.     

The detection of a strong influence of composition variations on low-temperature magnetic ordering in nearly stoichiometric Fe–V–Al alloys

The magnetic state of Fe–V–Al alloys with nearly stoichiometric (Fe₂VAl) compositions varying with respect both to aluminum and transition elements was studied. The effect of strong qualitative change in the magnetic properties induced by small variations of the composition was observed for the first time and analyzed. The key result is the detection of ferromagnetic ordering with a relatively high (~50 K) Curie temperature in an alloy with V atoms substituted in the lattice by Al atoms and the Fe content corresponding to the stoichiometric composition.     

Thermodynamic analysis of the characteristics of the plasmochemical synthesis of yttrium oxide

The nonmonotoneity of the dependence of the end product yield and the specific enthalpy on the pressure and temperature during plasmochemical synthesis of yttrium oxide is established. Optimal pressures are determined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 6, pp. 1063–1967, December, 1979.     

Scale factor in determining the hardness of metal materials

The method and the results of investigations into the effect of the scale factor on the hardness characteristics measured by the Vickers and Brinell methods at the macro- and microlevels of indentation of standard steel plates with different hardness values are described. The forcing-in load and the indenter diameter at which the hardness values increase abruptly are determined. Dependences are proposed for converting the Vickers hardness values at different forcing-in loads and the Brinell hardness values at different diameters of the indenter on condition of an equal degree of loading or an equal ratio between the diameters of the indentation and the indenter.     

Comparative thermodynamic analysis of plasmochemical synthesis of aluminum and yttrium oxides

A thermodynamic calculation of the dependence of the end-product yield and specific enthalpy on the pressure and temperature is performed for the plasmochemical synthesis of aluminum and yttrium oxides.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 1, pp. 143–146, January, 1981.     

Electron Structure and Optical Properties of the Mn<Subscript>1.8</Subscript>Co<Subscript>1.2</Subscript>Al Alloy and Spin Gapless Semiconductor State

This paper studies the optical properties of the Mn_1.8Co_1.2Al alloy, whose composition is close to that of spin gapless Mn₂CoAl semiconductor. Our investigation found the absence of intraband absorption contribution, which is an anomalous behavior of optical properties of the alloy. The presence of intense interband absorption in the IR range of spectrum indicates the existence of low-energy gap in the band spectrum of the alloy, which was found by electron structure calculations of the Mn_1.75Co_1.25Al alloy.     

Temperature breakdown phenomenon in tungsten single crystals at high magnetic fields

The transverse magnetoresistance and the Hall effect of tungsten single crystals with resistivity ratios of up to 95 000 were measured in the temperature range from 4.2 to 60 K and in magnetic, fields up to 15 T. It is shown that anomalies of the galvanomagnetic properties appear under strong intersheet electron-phonon scattering conditions. An exponential temperature dependence of the magnetoresistance (Peierls' exponent) is observed; the type of the field dependence of the magnetoresistance depends on the transport current direction in the crystal; the temperature behaviour of the Hall coefficient is determined by the type of the electron quasiorbits prevailing under these conditions. The data allow us to conclude that the temperature breakdown effect, i.e. a fundamental change of the electron trajectories in high magnetic fields, takes place in tungsten single crystals under conditions of intersheet electron-phonon scattering.