Electrical conductivity of Ag<Subscript>8</Subscript>SnS<Subscript>6</Subscript>-Ag<Subscript>2</Subscript>SnS<Subscript>3</Subscript>-AgBr alloys

The electrical conductivity of Ag₈SnS₆-[(AgBr)₄ · SnS₂] alloys in the Ag₈SnS₆-Ag₂SnS₃-AgBr system has been measured by a dc probe method between 210 and 380 K. The non-Arrhenius behavior of their conductivity is attributed to the fact that electrical and mass transport processes in these alloys involve both silver cations and bromide anions.     

Synthesis and crystal structure determination of Br<Subscript>2</Subscript>SeIBr polyhalogen-chalcogen

In this paper polyhalogen-chalcogen Br₂SeIBr was synthesized and the crystal structure was determined by single crystal X-ray diffraction method. This compound was prepared in the temperature range 150–50°C which was brownish-red in colour and crystallized in monoclinic crystal system and space groupP2_1/c with four molecules per unit cell. Lattice parameters were:a = 6.3711(1),b = 6.7522(2),c = 16.8850(5) Å, α = γ = 90°, β = 95.96°, ν = 722.45 ų.     

Phase relations in the LaB<Subscript>6</Subscript>-MoB<Subscript>2</Subscript> system

LaB₆-MoB_2.2 alloys have been prepared at 2600°C in high-purity helium in a vacuum induction furnace. As found by microstructural analysis and x-ray diffraction, the components of this system form a eutectic. The microstructure of the eutectic has been studied. MoB_2.2 is shown to undergo a transformation during cooling, with the precipitation of submicron-sized Mo₂B₅ and α-MoB particles. For this reason, its microhardness increases with an increase in the melting temperature of the alloys because the diffusion rate rises with temperature.     

Phase equilibria in the Ag<Subscript>2</Subscript>Se-AgAsSe<Subscript>2</Subscript>-AgBiSe<Subscript>2</Subscript> system

Phase equilibria in the pseudoternary system Ag₂Se-AgAsSe₂-AgBiSe₂ have been studied using differential thermal analysis, X-ray diffraction, microhardness tests, and emf measurements on silver concentration cells with Ag₄RbI₅ as solid electrolyte. The results are used to construct the 300-, 600-, and 800-K isothermal sections, a number of partial phase diagrams, and the liquidus projection. Several in- and univariant peritectic and eutectic equilibria and a broad region of AgBiSe₂-based solid solutions are identified. The homogeneity range of the high-temperature phase of AgBiSe₂ reaches −50 mol % in width (650 K), and that of the low-temperature phase is 20 mol % in width (300 K) along the AgAsSe₂-AgBiSe₂ constituent binary. The melting points, lattice parameters, and microhardness of the solid solutions are determined.     

Phase equilibria in the Ag<Subscript>2</Subscript>Se-As<Subscript>2</Subscript>Se<Subscript>3</Subscript>-Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> system

We have studied phase equilibria in the pseudoternary system Ag₂Se-As₂Se₃-Bi₂Se₃ and constructed the 300-, 600-, and 800-K isothermal sections, a number of partial phase diagrams, and the liquidus projection of this system. The AgAsSe₂-AgBiSe₂ and As₂Se₃-AgBiSe₂ joins are shown to be pseudobinary, and the Ag₃AsSe₃-AgBiSe₂ and AgAs₃Se₅-AgAsSe₂ joins are pseudobinary below the liquidus. Several in- and univariant peritectic, eutectic, and eutectoid equilibria and a broad region of AgBiSe₂-based solid solutions are identified. The homogeneity region of the AgBiSe₂-based phase has the largest extent along the AgAsSe₂-AgBiSe₂ join: 40 mol % (650 K) for the high-temperature form of AgBiSe₂ and 20 mol % (300 K) for its low-temperature form.     

Phase relations in the LaB<Subscript>6</Subscript>-W<Subscript>2</Subscript>B<Subscript>5</Subscript> system

The LaB₆-W₂B₅ join in the ternary system La-B-W is shown to have a eutectic phase diagram with t _e= 2220°C and a eutectic composition of 30 mol % LaB₆ + 70 mol % W₂B₅. Data are presented on LaB₆-containing systems potentially attractive for designing mixed-phase ceramics.     

Solid solutions in the Ag<Subscript>2</Subscript>Se-PbSe-Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> system

The phase equilibria in the pseudoternary system Ag₂Se-PbSe-Bi₂Se₃ have been studied using differential thermal analysis, x-ray diffraction, and microhardness measurements. The results have been used to construct the T-x phase diagram along the AgBiSe₂-PbSe join and the 900-K section of the ternary phase diagram. The AgBiSe₂-PbSe system contains a continuous series of cubic solid solutions with the NaCl structure. Their lattice parameter is an almost linear function of composition (a = 5.822–6.125 Å). The formation of the solid solutions stabilizes the high-temperature phase of AgBiSe₂: PbSe dissolution in this compound markedly reduces its polymorphic transformation temperature (590 K), down to room temperature at ? 10 mol % PbSe. In the Ag₂Se-PbSe-Bi₂Se₃ system, the γ-phase exists in a broad region around the AgBiSe₂-PbSe pseudobinary join.     

Effects of Pressure-Induced Phase Transition in Model Hg<Subscript>2</Subscript>Br<Subscript>2</Subscript> Ferroelastics

Raman spectra of model improper ferroelastics (Hg₂Br₂ crystals) have been analyzed in a wide range of hydrostatic pressures. The baric dependences of the phonon frequencies are obtained. The revealing and anomalous behavior of the soft mode, which is genetically related to the acoustic phonon (ТА₁) at the Brillouin zone boundary (point X) of the tetragonal phase, are most interesting. The buildup of the second acoustic phonon (ТА₂) from the same point has also been found in the ferroelastic-phase spectra, and its baric behavior has been investigated. The splitting of doubly degenerate phonons of the E_g symmetry has been revealed at fairly high pressures and explained.     

Phase relations in the TiO<Subscript>2</Subscript>-CsNO<Subscript>3</Subscript> system between 550 and 1140 K

We have studied reactions in the TiO₂-CsNO₃ system in the temperature range 550–1140 K in air using sample weight measurements, X-ray diffraction, electron microscopy, and electron probe microanalysis. The samples heat-treated at temperatures from 850 to 1140 K contained titanium cesium oxides.     

Phase relations and thermoelectric properties of alloys in the Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript>-Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> system

Using differential thermal analysis and x-ray diffraction, we have shown that the Bi₂Te₃-Bi₂Se₃ system contains a continuous series of solid solutions in a narrow temperature range and a compound of composition Bi₂Te₂Se below the solidus line. The liquidus and solidus lines determined using zone-melted samples differ little from those reported in the literature for equilibrium samples. The Bi₂Te_3?x Se _x solid-solution phase extends to ～-14 mol % Bi₂Se₃ (Bi₂Te_2.58Se_0.42). The thermoelectric power of the alloys drops sharply near the boundary of the two-phase region. Within the homogeneity range of Bi₂Te₂Se (33.3 mol % Bi₂Se₃), the thermoelectric power factor has a minimum, while the thermoelectric power has a small maximum.     

Phase relations in the TlInS<Subscript>2</Subscript>-TlYbS<Subscript>2</Subscript> system and electrical properties of Tl<Subscript>2</Subscript>InYbS<Subscript>4</Subscript> crystals

We have studied phase relations in the TlInS₂-TlYbS₂ system and showed that it contains a congruently melting compound of composition Tl₂InYbS₄ (1: 1 ratio of the constituent sulfides). According to X-ray diffraction results, the compound Tl₂InYbS₄ crystallizes in tetragonal symmetry. Temperature-dependent electrical conductivity and Hall data for Tl₂InYbS₄ single crystals demonstrate that this compound is a p-type semiconductor with a band gap of 1.60 eV. The temperature variation of the carrier Hall mobility in Tl₂InYbS₄ corresponds to carrier scattering by acoustic phonons.     

Phase relations and magnetic properties of alloys in the Co<Subscript>3</Subscript>Sn<Subscript>2</Subscript>-Bi system

The phase diagram of the Co₃Sn₂-Bi system has been constructed using physicochemical characterization techniques. The system is pseudobinary, with a limited series of Co₃Sn₂-based solid solutions (～7 at % Bi) and a liquid-liquid miscibility gap in the composition range ～14–88 at % Bi. A Co₃Sn₂-based solid solution containing about 7 at % Bi has been shown to possess spontaneous magnetization in the temperature range 80–400 K. Its Curie temperature exceeds 400 K.     

Synthesis,crystal structure and luminescence in Ca<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript>

Bluish green emitting phosphor, Ca₃Al₂O₆:Ce³⁺, is prepared by low-temperature combustion method. X-ray diffraction, photoluminescence, scanning electron microscopy techniques are used to characterize the synthesized phosphor. The most efficient bluish green (483 nm) emission is observed under the excitation by near UV light. The emission characteristics are credited to 5d → 4f type transitions in Ce³⁺. The luminescence properties of Eu²⁺ are predicted for the first time from those of Ce³⁺. Also, photoluminescence of Eu³⁺ is studied in the same host. The emission spectrum of Ca₃Al₂O₆:Eu³⁺ shows the peak at 592 (orange) and 614 nm (red) wavelengths. Ca₃Al₂O₆:Ce³⁺phosphor can be a potential blue phosphor for field emission display, solid-state lighting and LED.     

Beta-LaSc<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>: correction of the crystal structure

The published structure data of trigonal beta-LaSc₃(BO₃)₄ are incorrect because they are not compatible with the formula of the compound. After correcting the positional atom co-ordinates of one O atom the structure is found to be isotypic with CeSc₃(BO₃)₄ which crystallizes with the huntite CaMg₃(CO₃)₄ structure type.Response to paper, titled "Structure of medium temperature phase -LaSc₃(BO₃)₄ crystal," by He MY et al., published in MRI, vol. 2, issue 6, pp. 345–348, DOI     

Synthesis and crystal structure CoNi<Subscript>2</Subscript>(BO<Subscript>3</Subscript>)<Subscript>2</Subscript>

A new metal orthoborate compound, cobalt dinickel orthoborate, CoNi₂(BO₃)₂ has been successfully synthesized for the first time. The title compound was synthesized by thermally-induced solid-state chemical reaction at 900°C between the initial reagents of Co(NO₃)₂ · 6H₂O, Ni(NO₃)₂ · 6H₂O and H₃BO₃ which were mixed with the mol ratio of 1: 2: 2 respectively. The obtained product was structurally characterized by X-ray powder diffraction technique. It has been found that the CoNi₂(BO₃)₂ crystallizes in the kotoite type and isostructural with the compounds having the chemical formula M₃(BO₃)₂ where M—Mg, Co and Ni. The synthesized compound belongs to the orthorhombic crystal system with the refined unit cell parameters of a = 5.419(9) Å, b = 8.352(0) Å, c = 4.478(8) Å and Z = 2. The space group was determined as Pnmn. Further characterizations by FTIR, elemental analysis and thermal analysis were also performed.     

Improved photocatalytic degradation of organic dye using Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>/MoS<Subscript>2</Subscript> nanocomposite

Highly efficient Ag₃PO₄/MoS₂ nanocomposite photocatalyst was synthesized using a wet chemical route with a low weight percentage of highly exfoliated MoS₂ (0.1 wt.%) and monodispersed Ag₃PO₄ nanoparticles (~5.4 nm). The structural and optical properties of the nanocomposite were studied using various characterization techniques, such as XRD, TEM, Raman and absorption spectroscopy. The composite exhibits markedly enhanced photocatalytic activity with a low lamp power (60 W). Using this composite, a high kinetic rate constant (k) value of 0.244 min^-1 was found. It was observed that ~97.6% of dye degrade over the surface of nanocomposite catalyst within 15 min of illumination. The improved photocatalytic activity of Ag₃PO₄/MoS₂ nanocomposite is attributed to the efficient interfacial charge separation, which was supported by the PL results. Large surface area of MoS₂ nanosheets incorporated with well dispersed Ag₃PO₄ nanoparticles further increases charge separation, contributing to enhanced degradation efficiency. A possible mechanism for charge separation is also discussed.     

Electric-field effect on crystal growth in the Li<Subscript>3</Subscript>PO<Subscript>4</Subscript>-Li<Subscript>4</Subscript>GeO<Subscript>4</Subscript>-Li<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-LiF system

We have studied the electric-field effect on crystallization processes in the Li₃PO₄-Li₄GeO₄-Li₂MoO₄-LiF system. In zero field, Li_3+x P_1?x Ge _x O₄ (x = 0.31) crystals were grown on the cathode under the conditions of this study. At low applied voltages (≤ 0.5 V), we obtained Li₂MoO₄, Li₂GeO₃, and Li_1.3Mo₃O₈. In the range V = 0.5–1 V, crystals of Li_3+x P_1?x Ge _x O₄ solid solutions with x = 0.17, 0.25, 0.28, 0.29, and 0.36 were obtained. An applied electric field was shown to reduce the melting temperature of the starting mixtures and the crystallization onset temperature.     

Subsolidus phase relations in the system Tm<Subscript>2</Subscript>O<Subscript>3</Subscript>-Rh<Subscript>2</Subscript>O<Subscript>3</Subscript>

The Tm₂O₃-Rh₂O₃ system has been studied by x-ray diffraction, thermal analysis, and chemical analysis of annealed and quenched samples. The results have been used to construct a schematic subsolidus phase diagram of the system. Only one double oxide, TmRhO₃, has been identified. Some of its physicochemical properties are reported.     

X-ray diffraction study of compounds in the Ag<Subscript>2</Subscript>S-Cu<Subscript>2</Subscript>S system

Ag_1.55Cu_0.45S and Ag_0.93Cu_1.07S single crystals have been grown by the Bridgman method, and their polymorphic transformations have been studied by high-temperature x-ray diffraction.     

Phase equilibria in the K<Subscript>2</Subscript>O-MgO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Subsolidus (500–700°C) phase relations in the K₂O-MgO-B₂O₃ system have been studied by X-ray diffraction. The results are used to construct the phase compatibility diagram of the K₂O-MgO-B₂O₃ system in the range 650–700°C. A new ternary compound of composition K₂Mg₃B₂O₇, with the constituent oxides in the molar ratio 1: 3: 1, is identified.