The structural features of the germanium-silicon solid solution crystals obtained under microgravity

Structural features of germanium-silicon solid solution crystals have been investigated and silicon distribution in the crystals has been studied. All the crystals obtained under microgravity had, in spite of good external shape and facetting, a poorer internal structure than those obtained on Earth. The distribution of silicon have been shown to be non-uniform. High dislocation densities were observed.     

Gravitational Sensitivity of Solutions–Melts at the Crystallization of Two-Phase InSb–InBi Alloys under Space Conditions

Analyzing the results of space and ground-based experiments carried out in the Baikov Institute of Metallurgy and Materials Science to study the processes of the melting and crystallization of two-phase InSb–InBi alloys of an indium–antimony–bismuth (In–Sb– Bi) triple system, we have demonstrated the gravitational sensitivity of the InSb-based solution– melt. It manifests itself as a certain asymmetry of the boundary of the dissolution of the InSb ingot by the InSb–InBi melt and heterogeneity of the melt along this boundary depending on the magnitude and direction of the gravity force acceleration gin the range (1–10^–3–10^–5)g ₀, where g ₀is the acceleration of the gravity force on Earth. For the first time, it is established in the experiments under analysis that the homogeneity of melts of a complex composition with components of various densities can be reached only at magnitudes of quasistationary (residual) microaccelerations g< 10^–6 g ₀.     

Time variations of high energy gamma emission of Vela Pulsar observed by GAMMA-1 telescope

Two observations of the Vela Pulsar in the energy range 50–5000 MeV performed with the GAMMA-1 telescope in 1990 and 1991 allowed us to study time variability of the pulsar light curve and energy spectra. The light curve for E_γ > 50 MeV shows definite variations in the first interpeak phase interval. The energy spectra of the two main peaks and first interpeak in the lightcurve vary significantly below 200 MeV.     

Crystallization of germanium-silicon solid solution from the vapour phase in microgravity conditions

Mass transport has been investigated in the closed system Ge-Si-Br used for preparing germanium-silicon solid solution crystals by chemical transport reaction method in space. It has been shown that the experimental rate of mass transport may be analytically described in proposing a pure diffusion mechanism. In space, growth of needles and whiskers occured without practically formation of a polycrystalline layer characteristic of on-earth experiments.     

Solidification of GeSi solid solution in near-zero-G conditions

In summary, it should be stated that the existing theories of segregation during directional crystallization which consider mass transport in melt due only to either concentration diffusion or convective stirring (or both) cannot account for solute segregation picture observed in solid solution crystals which have been obtained aboard Apollo-Soyuz orbital complex. To do this, some other, new models are required.     

Influence of Microaccelerations on the Impurity Distribution in the InSb:Te Crystals Grown in Orbital Flights by the Method of Floating Zone Melting

The periodicity of the structure of impurity heterogeneities in the longitudinal section of an indium antimonide monocrystal doped by tellurium (InSb:Te) is investigated. The monocrystal was grown by the method of floating zone melting onboard the Foton-3 satellite. It is shown that the frequencies of harmonic components of heterogeneities converted into the time region coincide with frequencies of microaccelerations in the range 0–0.005 Hz arising onboard the Foton satellites. This fact confirms the hypothesis stated previously that residual microaccelerations onboard the satellite were the cause of occurrence of indicated periodicities.     

Geminga pulsar observations with gamma-telescope Gamma-1

The Geminga light curve obtained with the “Gamma-1” telescope features two peaks separated by 0.5 ± 0.03 period. The light curve is pronounced for γ-quanta energies higher than 400 MeV. The pulsed flux upper limit (1σ) in the energy interval 50 – 300 MeV is 6·10⁻⁷ cm⁻²sec⁻¹. For energies >300 MeV the pulsed component power law spectrum has an exponent 1.1 _−0.3^+1.1 and an integral flux (1.1±0.3)·10⁻⁶ cm⁻²sec⁻¹.     

The Influence of Arrangement of Growth Setups onboard a Spacecraft on Microgravity Conditions of Experiments: An Example of Floating Zone Melting of InSb:Te onboard the Foton-3 Satellite

The results of experiments on the growth of InSb:Te by the floating zone melting in the Zona-4 setup during a flight of the Foton-3 satellite are discussed in comparison with the data on the microgravity situation typical for satellites of this type. When analyzing inhomogeneities in the crystals obtained, we reveal the frequencies corresponding to periodical variations of the impurity channel position (the facet effect), to interleaving of packs in which the growth layers are grouped, and to location of subgroups of the growth layers inside the packs. These frequencies are close to those discovered during measurements of low-frequency (quasistationary) microaccelerations (g) onboard the spacecraft Foton-8, Foton-10, Foton-11, and Foton-12. Calculated values of g at the place where the Zona-4 setup is installed confirm the possibility of impact of such g on the heat and mass transfer in the melt.     

Gravitational Sensitivity of Melts at the Growth of InSb:Te Crystals by the Bridgman and Floating Zone Methods under the Conditions of Microgravity

The comparative analysis of the results of space and ground-based experiments IMET RAS on the growth of InSb:Te crystals by the Bridgman method and floating zone method (FZM) is made for the purpose of studying the influence of microgravity on the growth, structure, and properties of grown crystals, and thus the gravity sensitivity of InSb melt is demonstrated. It is shown that, under microgravity conditions, the Bridgman method makes it possible to grow InSb:Te crystals without contact with the ampoule walls, which provides for the single crystal structure, the absence of striations, and a low dislocation density. For the first time, InSb:Te monocrystals were grown with the FZM under microgravity. The anomalous behavior of the impurity core (facet effect) in these crystals correlates with the changed magnitude and direction of the quasi-stationary (residual) microaccelerations.