Vol 52, No 5 (2016)

We have studied the physical properties of Hg_{1 − x − y}Cd_xGd_ySe crystals grown by the Bridgman method. The Hg_{1 − x − y}Cd_xGd_ySe crystals are shown to be n-type. Their Hall coefficient is temperature-independent, which points to electron gas degeneracy. The optical band gap of the crystals has been determined. The behavior of their magnetic susceptibility can be accounted for by the presence of clusters of various sizes.

The phase composition of the carbonatization products of nanocrystalline KO₂ deposited on a glass fiber matrix has been studied using differential thermal analysis, X-ray diffractometry, and Raman spectroscopy. The results demonstrate that the possible carbonatization products of potassium superoxide and alkali nanocrystals are potassium carbonate (K₂CO₃), potassium bicarbonate (KHCO₃), and mixtures of these, depending on the reaction temperature. No new phases or chemical compounds with glass fiber were detected.

We have studied the effect of aging conditions on the properties of titania hydrosols produced via ultrasonic processing and containing aggregates of 5-nm-diameter amorphous particles. The results demonstrate that, at room-temperature, 0.44 M to 0.11 M hydrosols are stable for 3 to 22 days. During aging for 40 to 45 days, the properties of 0.01 M to 0.0025 M hydrosols remain unchanged. Aging for a longer time causes the amorphous particles to crystallize in the anatase structure. Raising the temperature to 75°C reduces the induction time to 3–4 h.

Order–disorder transitions in xR₂O₃ · (1 − x)TiO₂ (R = Sc, 0.4 ≤ x ≤ 0.5; R = Y, 0.5 ≤ x ≤ 0.6) solid solutions with highly imperfect fluorite-derived structures have been studied using monochromatic synchrotron X-ray diffraction and Raman spectroscopy. The results demonstrate that the synthesis process leads to the formation of a fluorite-like (Fm3m) disordered phase and a nanoscale (~10–100 nm) pyrochlore-like (Fd3m) ordered phase of the same composition, coherent with the disordered phase. We have determined their lattice parameters. The Raman spectra of Sc₂TiO₅ (Y₂TiO₅) contain broad lines in low- and high-frequency regions: at 190, 350, and 775 (134, 188, 365, 404, and 727) cm⁻¹. These lines are characteristic of a pyrochlore-like phase with a varying degree of order and a disordered fluorite-like phase, respectively. The pyrochlore-like phase Y₂Ti₂O₇ has two strong Raman peaks in the low-frequency region: at 312 and 527 cm⁻¹. The formation of nanodomains with different degrees of order is caused by the internal stress that arises from the high density of structural defects in the unit cells of the solid solutions.

Europium-doped YVO₄ phosphors have been synthesized using microwave radiation of 700 W power. The uniformity and high rate of microwave heating, as well as “nonthermal” effects of microwave radiation, considerably accelerate the decomposition of precursors and YVO₄:Eu³⁺ synthesis. The europium concentration was varied from 1 to 8 at %. The luminescence intensity of YVO₄:Eu³⁺ was shown to depend on Eu³⁺ concentration, with a maximum at 8 at % Eu³⁺. According to transmission electron microscopy data, the synthesized phosphors consist of nanoparticles 6 to 8 nm in size, with an appreciable degree of agglomeration.

We have developed a process for the synthesis of Ni(II) and Zn(II) triuranates with the general formula M^IIU₃O₁₀ · 6H₂O through reaction of schoepite, UO₃ · 2.25H₂O, with aqueous solutions of nickel and zinc nitrates under hydrothermal conditions. Using chemical analysis, X-ray diffraction, IR spectroscopy, and thermal analysis, we have determined the composition and structure of the triuranates and investigated their dehydration and thermal decomposition.

High-entropy melts in the Cu—Bi—Sn—In—Pb system have been studied by viscosity measurements during heating and subsequent cooling. The experimental data have been used to determine the temperatures at which microinhomogeneities in the melts irreversibly disappear.

Using mechanochemical synthesis through milling of equiatomic multicomponent mixtures of Cr, Fe, Co, Ni, Al, Ti, Mo, and Nb metals in various combinations, we have synthesized powder alloys with different phase compositions: amorphous phase (AP), AP + BCC phase, AP + BCC phase + MO, and FCC + BCC phases. The FCC phase has been shown to be a Ni-based solid solution. The presence of aluminum in a starting mixture helps to stabilize the BCC phase owing to the formation of a disordered B2 phase. Al dissolves in both the BCC and FCC solid solutions, increasing their lattice parameters. In Al-free starting mixtures, Cr is responsible for the formation of the BCC solid solution. The formation of an AP during milling of multicomponent mixtures is favored by the presence of transition metals with a large atomic radius: Ti, Mo, and Nb.