Inorganic Materials (v.51, #3)

Contribution of the free energy of the three-phase line of contact to the thermodynamic equilibrium conditions of a metal solvent droplet in Si and Ge whisker growth by V. A. Nebol’sin; D. B. Suyatin; A. I. Dunaev; S. S. Shmakova; M. A. Zavalishin; E. V. Ivannikova (191-196).
Analysis of the shape of the lateral surface of whiskers and the vapor-liquid-solid three-phase line of contact along the wetting perimeter of a metal solvent droplet indicates that the contribution of the free energy related to the line tension on the three-phase line of contact to the thermodynamic equilibrium conditions of the metal solvent droplet in whisker growth leads to a substantial increase in the energy barrier for droplet formation because of the action of the line tension. The shape of the three-phase line of contact suggests that the droplet is in a liquid-solid state of aggregation.

We have studied carrier transport in n-GaAs/n +-Al0.35Ga0.65As/i-GaAs/InAs-QD/i-GaAs/n +-GaAs/GaAs(SI) multilayer heterostructures grown by ion beam crystallization. The results demonstrate that, at a temperature of 300 K, the dominant mechanisms of carrier transport from the quantum dots are thermionic emission (at bias voltages under 0.5 V) and electric field-assisted tunneling (at bias voltages above 0.5 V). At a temperature of 90 K and forward bias voltages under 0.25 V, the background drift current prevails. In the range 0.25–1 V, we observe drift current saturation and an increase in the contribution of the tunneling current. At bias voltages above 1 V, the electric field-assisted tunneling current prevails. A narrow photoluminescence peak observed at 1.18 eV (T = 90 K) points to interband recombination through the ground state in the InAs quantum dots. Weak features at 1.23 and 1.29 eV correspond to weak recombination through excited states of the quantum dots.

α-Al2O3 powders from amorphous alumina gel by A. V. Galakhov; V. A. Zelenskii; N. A. Alad’ev; L. V. Kovalenko (201-205).
We have studied the properties of α-Al2O3 powders prepared from amorphous alumina gel. The powders have a small particle size owing to the low synthesis temperature. The sintering temperature of compacts produced by pressing the powders is lower than that in the case of powders prepared from hydroxide precursors. The sintered material has a homogeneous, fine-grained microstructure, which ensures excellent mechanical properties.

Fiber-forming organoyttroxanealumoxanes by G. I. Shcherbakova; T. L. Apukhtina; N. S. Krivtsova; M. S. Varfolomeev; D. V. Sidorov; P. A. Storozhenko (206-214).
We demonstrate that organoyttroxanealumoxanes with the general formula [Al(OR) l (OR*) x (OH) z O y ] m · [(R**O) s Y(OH) t O r ] k , where m/k < 200, possess fiber-forming properties, which allows one to use them as precursors to yttria-doped alumina-based refractory fibers, including those identical in composition to yttrium aluminum garnet, Al5Y3O12 [1].

We have studied the effect of disodium EDTA concentration on the size and zeta potential of CdS nanoparticles in a stable aqueous solution. Measurement results demonstrate that the colloidal solution remains stable at initial Cd2+ and S2− concentrations of 8 mM and initial EDTA concentrations in the range 3.2 to 16 mM. The reactant mixing sequence is shown to influence the ionic state of EDTA in solution, which in turn influences the stabilization mechanism of the CdS nanoparticles. At pH 3, we observe the formation of protonated chelates such as [CdHY], which may form a [-S-Cd-EDTA] ternary complex with the surface of a nanoparticle, thereby ensuring stability of the colloidal solution at a twofold excess of EDTA. Analysis of the nanoparticle size distribution evaluated by dynamic light scattering measurements indicates that the minimum hydrodynamic diameter of the nanoparticles is 10 ± 3 nm. The corresponding zeta potential is about −20 mV.

Electrical conductivity and thermoelectric power of (TlInSe2)0.2(TlGaTe2)0.8 crystals by S. N. Mustafaeva; M. M. Asadov; A. I. Jabbarov; E. M. Kerimova (220-224).
The compounds TlInSe2 and TlGaTe2 have been prepared by direct elemental synthesis, and the (TlInSe2)0.2(TlGaTe2)0.8 solid solution has been synthesized from them. Crystals of the (TlInSe2)0.2(TlGaTe2)0.8 solid solution with a tetragonal structure have been grown, and their dc electrical conductivity and thermo-electric power have been measured in the temperature range 77–347 K. The results demonstrate that, at low temperatures, in the region of hopping conduction, the thermoelectric power of (TlInSe2)0.2(TlGaTe2)0.8 is proportional to T. With increasing temperature, the thermoelectric power becomes inversely proportional to temperature when the conductivity begins to be dominated by charge carriers excited to the allowed band.

An electrically conductive boron-doped diamond material with high thermal stability and good mechanical properties has been synthesized at high pressures from powder mixtures of graphite and boron carbide. Specific microstructure and high elastic moduli of samples obtained indicate the formation of polycrystalline diamond matrix in the material. The unique combination of physicochemical properties offered by heavily boron-doped diamond can extend its application area as an electrostructural material capable of operating in aggressive media.

We have studied the stability of ultradispersed diamond and carbon nanotube suspensions in water and aqueous solutions of various salt electrolytes. The results demonstrate that, in the course of coagulation and sedimentation, the particles in suspension become separated into size fractions and form agglomerates several orders of magnitude greater in size than the parent particles, and that the dependence of the suspension concentration on storage time has a linear portion. The sedimentation process in the electrolyte solution-based suspensions proceeds until an almost zero concentration of fine particles is reached. We have determined the settling time of the particles in the suspensions, which determines their stability, and evaluated the porosity of particle conglomerates. The feasibility of suspension redispersion after sedimentation has been examined. Resonication of the suspensions has been shown to restore the particle concentration and size.

Efficient synthesis of aluminum- and zinc-containing metal-organic frameworks by E. A. Vlasova; E. V. Naidenko; E. V. Kudrik; A. S. Makarova; S. V. Makarov (236-240).
A convenient method has been proposed for the synthesis of aluminum- and zinc-containing terephthalic acid-based metal-organic frameworks. The method offers high productivity and high product yield. Materials produced by this method have been characterized by physicochemical techniques, and their sorption capacity has been assessed.

Preparation of a mixture of tellurium(IV), molybdenum(VI), and bismuth(III) hydroxides by coprecipitation from aqueous solutions by A. A. Sibirkin; O. A. Zamyatin; E. V. Torokhova; I. G. Goreva; M. F. Churbanov; A. I. Suchkov; A. N. Moiseev (241-244).
Precipitates of tellurium(IV), molybdenum(VI), and bismuth(III) compounds of controlled composition have been obtained by precipitation from hydrochloric acid solutions of tellurium dioxide, ammonium heptamolybdate, and dibismuth trioxide. We have examined the general aspects of the macrocomponent distribution between the precipitate and solution and found conditions of a sufficiently complete tellurium(IV), molybdenum(VI), and bismuth(III) precipitation in a weakly acidic medium. After drying and calcination, the precipitates thus obtained were used as starting mixtures for the preparation of TeO2-MoO3-Bi2O3 glasses.

We report structure refinement results for Sr5(VO4)3Br (a = 10.2793(2) Å, c = 7.32089(8) Å, V = 669.92(2) Å3; R wp = 3.17%; R p = 2.39%) and thermal expansion data for nine strontium apatites. An increase in the ionic radius of the halogen in the apatites is accompanied by a change in its crystallographic site and, as a consequence, an increase in linear thermal expansion coefficients and thermal expansion anisotropy parameter (α a c ). A monoclinic phase of Sr5(CrO4)3Cl has been identified for the first time, which has negative linear thermal expansion coefficients along the crystallographic axis c. The volume expansivity of the strontium apatites correlates with their anisotropy parameter.

This paper examines the structure and transport properties of Na-β″-Al2O3-based ceramic electrolytes synthesized from plasma synthesis products. The chemical composition of sodium polyaluminate nanopowders was varied in the ranges 6.5–9.3 wt % Na2O, 0.7–0.8 wt % Li2O, and 89.9–92.8 wt % Al2O3, at a phase ratio β″/(β″ + β) = 0.83–1.00. Data are presented on the formation of a highly conductive β″-phase with a rhombohedral structure, equilibrium chemical composition, and hexagonal unit cell parameters a = 0.5587(8) nm and c = 3.342(3) nm in the system in question during sintering and annealing. The phase formation dynamics are shown to be determined by the initial composition of the powders. The 573-K ionic conductivity of β″-alumina solid electrolytes with the compositions Na(1.53–1.73)Li(0.28–0.32)Al(10.66–10.72)O17 and a relative density of at least 99% ranges from 25 to 33 S/m, with an activation energy for conduction ΔE a = 0.15–0.20 eV.

The magnetic susceptibility of single crystals of Bi2Te3-Sb2Te3 solid solutions containing 10, 25, and 50 mol % Sb2Te3 has been measured using a superconducting Josephson interferometer in the temperature range from 2 to 400 K at 3-K intervals in magnetic fields of up to 2.38 × 106 A/m at two orientations of the magnetic field H with respect to the trigonal axis C 3 of the crystals (HC 3 and HC 3) with a relative uncertainty within 2%. A new approach has been proposed for separately assessing the contributions of the ionic core and free charge carriers to the magnetic susceptibility, which uses experimental data on magnetic susceptibility and effective mass anisotropy. Analysis of the data obtained in this study demonstrates that the temperature variation of carrier susceptibility in the region of degenerate and nondegenerate states of the electronic system can be described in terms of the Pauli and Landau-Peierls approaches if one takes into account the complex structure of the valence band and “nonparabolicity” of the light hole energy spectrum.

Bi1 − x Nd x Fe1 − x Mn x O3 (0.03 ≤ x ≤ 0.21) solid solutions have been synthesized, and their crystal structure, thermal expansion, and electrical transport properties have been studied. The results demonstrate that the solid solutions have a rhombohedrally distorted and an orthorhombically distorted perovskite structure for x < 0.12 and x > 0.12, respectively, and that their unit-cell parameters decrease with increasing x. The Bi1 − x Nd x Fe1 − x Mn x O3 solid solutions are shown to be p-type semiconductors, whose electrical conductivity increases with increasing x. The linear thermal expansion coefficient of the rhombohedrally and orthorhombically distorted solid solutions is (12.8–13.3) × 10−6 and (10.0–11.7) × 10−6 K−1, respectively.

Specific absorption coefficient of nickel in (TeO2)0.80(MoO3)0.20 glass by O. A. Zamyatin; M. F. Churbanov; V. G. Plotnichenko; A. A. Sibirkin; I. G. Goreva (278-282).
We have prepared (TeO2)0.80(MoO3)0.20 tellurite glass samples containing 0.02–0.5 wt % nickel and investigated their optical transmission in the range 450–2800 nm. The transmission spectra of the glasses contain absorption bands centered at 810 and 1320 nm. From the composition dependence of the absorption coefficient, we have evaluated the specific absorption coefficient of Ni2+ in the range 600–2800 nm. It has been found to be 20.6 ± 0.4 cm−1/wt % at the maximum of the 1320-nm absorption band.

Photoactivated nanocrystallization and hardness of Fe78P20Si2 alloy by M. S. Antonova; E. K. Belonogov; A. V. Boryak; V. V. Vavilova; V. M. Ievlev; S. V. Kannykin; N. A. Palii (283-287).
The structural changes induced in an amorphous Fe78P20Si2 alloy by heat treatment and lamp processing have been compared using X-ray diffraction. The results demonstrate that the main effect of the lamp processing is to increase the crystallization rate. Under nanoindentation conditions that do not lead to crystallization under the action of a concentrated load (as verified by transmission electron microscopy), we have determined the hardness (8 ± 0.3 GPa) and Young’s modulus (130 ± 10 GPa) of the amorphous alloy. Lamp processing conditions have been found that lead to the formation of an amorphous-nanocrystalline composite whose hardness is almost twice that of the parent amorphous alloy, without loss of plasticity.

Phase transformations in the Nd-Mn-O system by L. B. Vedmid’; A. M. Yankin; O. M. Fedorova; V. M. Kozin (288-293).
The sequence of phase transformations responsible for the dissociation of the compounds NdMn2O5 and NdMnO3 in the Nd-Mn-O system has been identified by a static technique at a reduced oxygen pressure in combination with thermal analysis and high-temperature X-ray diffraction. We have mapped out the p-T-x (oxygen pressure-temperature-composition) phase diagram of the Nd-Mn-O system and determined the thermodynamic characteristics of formation of the compounds NdMn2O5 and NdMnO3 from their constituent elements.

Electrochemical deposition of contact structures for integrated circuit packaging by V. M. Roshchin; V. L. Dshkhunyan; I. N. Petukhov; K. S. Sen’chenko; V. R. Kukhtyaeva (294-298).
This paper considers electrochemical tin deposition for producing contact elements in integrated circuit packaging. We examine the effect of organic additives to sulfate electrolytes on the growth of local vertical structures, with the aim of suppressing lateral growth of the deposit.