Analysis of thermodynamic properties and phase equilibria in the Si-P system

A self-consistent analysis of the available data on thermodynamic properties and phase equilibria in the Si-P system is performed. Thermodynamic properties of solid and liquid solutions of phosphorus in silicon are approximated on the basis of the concepts of dilute and ideal associated solutions. The thermodynamic properties and phase boundaries in the range of compositions 0 ≤ x(P) ≤ 0.5 are adequately described.     

Synthesis and X-ray diffraction study of complex oxides of the Zn2 ? x(ZraSnb)1 ? xFe2xO4 composition

A multicomponent system of complex refractory oxides of the composition Zn_{2 − x} (Zr _a Sn _b )_{1 − x} Fe_2x O₄ (a + b = 1; a: b = 1: 5, 1: 4, 1: 3, 1: 2, 1: 1, 2: 1, 3: 1, 4: 1; x = 0−1.0; Δx = 0.05) was studied by X-ray diffraction. The samples were prepared from oxides of appropriate metals by low-temperature plasma synthesis (hydrogen-oxygen flame). Two phases with wide homogeneity ranges were identified: α phase crystallized in the crystal system of inverse cubic spinel and β phase with the structure of tetragonal spinel. The phase boundaries were found. Structural data are presented for about 100 solid solutions.     

Electroconduction of Solid Solutions Na3 – 2x M x PO4(M = Cd, Pb)

In the sodium-orthophosphate-based solid solutions in Na_{3 – 2x} M _x PO₄ systems (M = Cd, Pb), the electroconduction is maximum near the upper concentration boundaries of the single-phase regions: x 0.4 for M = Cd and x 0.25 for M = Pb. The conductivity values at 300°C are 6.25 × 10^–3 and 2.5 × 10^–3 S/cm, respectively. The conduction of synthesized solid electrolytes has a co-cation nature. Their electric characteristics, inferior to those of the Na₃PO₄-based solid solutions obtained via heterovalent substitutions of another type, may be a manifestation of an effect similar to the polyalkali effect.     

Physicochemical and Catalytic Properties of La1 – xCaxFeO3 – 0.5x Perovskites Prepared Using Mechanochemical Activation

The phase composition of La_{1 – x} Ca _x FeO_{3 – 0.5x} perovskites synthesized from preactivated oxides was studied by powder X-ray diffraction analysis and differential dissolution. The system does not form a continuous series of homogeneous solid solutions. No intermediate samples from this series are monophasic. It was found that the synthesis under nonequilibrium conditions (mechanical activation + calcination at 900° for 4 h) resulted in nonequilibrium microheterogeneous solid solutions with degrees of calcium substitution for lanthanum of no higher than 0.5. A longer calcination (for 16 h) or an increase in the calcination temperature of solutions up to 1100 ° decreased the calcium content of the samples down to x 0.2 because of the formation of a brownmillerite phase. The catalytic activity of the test samples in the oxidation of CO changed nonmonotonically with x, and it was maximum at x = 0.5–0.6, which correlates with the maximum density of interphase boundaries in these samples.     

Modified headspace solid‐phase microextraction for the determination of quantitative relationships between components of mixtures consisting of alcohols,esters, and ethers — impact of the vapor pressure difference of the compounds

The quantitative relationship between analytes established by the headspace solid‐phase microextraction procedure for multicomponent mixtures depends not only on the character and strength of interactions of individual components with solid‐phase microextraction fiber but also on their vapor pressure in the applied headspace solid‐phase microextraction system. This study proves that vapor pressure is of minor importance when the sample is dissolved/suspended in a low‐volatility liquid of the same physicochemical character as that of the used solid phase microextraction fiber coating. It is demonstrated for mixtures of alcohols, esters, ethers and their selected representatives by applying a headspace solid‐phase microextraction system composed of Carbowax fiber and sample solutions in polyethyleneglycol. The observed differences in quantitative relations between components of the examined mixtures established by their direct analysis and by modified headspace solid‐phase microextraction are insignificant (F _exp < F _crit). It is explained by a significant diminution in vapor pressure difference between individual components of the examined mixture in the applied headspace solid phase microextraction system due to low components concentration in polyethyleneglycol suspensions (Raoult's law) and due to strong specific interactions of analyte molecules with polyethyleneglycol molecules.     

Electronic structure and Mn<Emphasis Type="Italic">K</Emphasis> absorption spectra of MnO clusters in nanocomposites

The products of the thermobaric treatment (P = 1–4 GPa, T = 2000°C) of the ultrafine powder Re_0.67Rh_0.33 (crystallite size 50 Å) were studied. For one of the products, the (Vickers) microhardness is 1200 kg/mm², which is significantly higher than the literature values for alloys in the Re-Rh system. This effect is attributed to the formation of a binary carbide with an anti-NiAs type of structure.     

State of atoms and interatomic interactions in complex perovskite-like oxides: XXXI. Influence of magnesium concentration on chromium atoms state and interatomic interactions in lanthanum gallate doped with chromium and magnesium

Magnetic susceptibility of LaCr _x Ga_1−1.2x Mg_0.2x O_3−δ and LaCr _x Ga_1−1.5x Mg_0.5x O_3−δ solid solutions with the ratios [Cr]:[Mg] = 5:1 and 2:1 was studied. Fractions of clusters and single chromium atoms were calculated for the series of solid solutions with [Cr]:[Mg] = 5:1. The relation of the systems with [Cr]:[Mg] = 5:1 and [Cr]:[Sr]:[Mg] = 5:1:1 was revealed. For the system with [Cr]:[Mg] = 2:1 a temperature dependence of effective magnetic moment was found, which suggests that the exchange parameter is temperature dependent.     

Potassium Cationic Conduction in K3 – xP1 – xExO4 (E = S,Cr, Mo,W)

Solid solutions of cubic structure based on K₃PO₄are synthesized in the systems K_{3 – x} P_{1 – x} E _x O₄(E = S, Cr, Mo, W). Approximate boundaries of single-phase regions and the temperature and concentration dependences of electroconductivity are studied. The transport numbers, measured by a modified Tubandt method, confirm a potassium cationic character of conduction. Electric parameters of the electrolytes are compared with those of sodium and rubidium conducting solid solutions in similar systems. Factors that affect transport properties of synthesized phases are discussed.     

Potassium–conducting K<Subscript>1 − 2<Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>GaO<Subscript>2</Subscript> solid electrolytes

Solid electrolytes with potassium-cation conductivity in the K_{1 − 2x} Pb _x GaO₂ system were synthesized and studied. It was found that solid solutions based on potassium monogallate are formed in a wide range of compositions. They contain vacancies in the potassium sublattice that provide for high conductivity of electrolytes. The relationship is considered between electric characteristics of solid electrolytes and the composition and structure of solid solutions. The results are compared to the earlier obtained data for similar solid electrolytes based on potassium monoaluminate and monoferrite.     

Solid electrolytes based on CeO<Subscript>2</Subscript> for medium-temperature electrochemical devices

CeO₂-based solid solutions with a fluorite structure are promising materials as electrolytes of medium-temperature electrochemical devices: electrolytic cells, oxygen sensors, and solid oxide fuel cells. In this work, studies are presented of the effect of the dopant cation radius and its concentration on the physico-chemical properties of the Ce_{1 − x} Ln _x O_{2 − δ} solid solutions (x = 0–0.20; Ln = La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) and also of multicomponent solid solutions of Ce_{1 − x} Ln _x/2Ln′ _x/2O_{2 − δ} (x = 0–0.20; Ln = Sm, La, Gd and Ln′ = Dy, Nd, Y) and Ce_{1 − x − y} Sm _x M _y O_{2 − δ} (M = Ca, Sr, Ba) obtained using the solid-phase synthesis technique. Electric properties of the samples were studied in the temperature range of 623–1173 K and in the oxygen partial pressure range of 0.01–10⁻²² MPa. The values of oxygen critical pressure ( p_O2 ^* )\left( {p_{O_2 }^* } \right) are presented, at which the ionic and electron conductivity values are equal. The values were calculated on the basis of experimental dependences at 1023 K at the assumption that the ionic conductivity value is determined only by the dopant concentration and its effective ionic radius and is independent of the oxygen partial pressure.     

X-Ray Photoelectron Spectra and Electronic Structure of Solid Solutions Based on Cubic Boron Nitride

The electronic energy structure of substitution solid solutions based on boron nitride B _1-x NR _x and BN _1-x R_x (R = C, O) (x=0.25) in a diamond-like modification of ZnS type has been investigated by the local coherent potential method in terms of multiple-scattering theory. The total and partial densities of states were calculated for each element in a solid solution. The crystalline potential was calculated using an MT approximation. The lattice parameter was chosen based on X-ray diffraction data for c-BN: 0.3615 nm. The electronic energy structures of the solid solutions and binary c-BN are compared in the framework of a single approximation. The calculated partial densities of states are compared with the experimental X-ray emission and photoelectron spectra of boron, nitrogen, and oxygen in these compounds. The calculated partial charges of electrons at the top of the valence band show that charge transfer from boron to nitrogen takes place in the solid solutions. An analysis of the electronic structures of the solid solutions of boron nitride indicates that the quasicore resonances inherent in binary c-BN are delocalized and that chemical bonding in the solid solutions of boron nitride is weakened.     

Chemical dissolution of CdTe and Cd1-x ZnxTe solid solution single crystals in bromine etchants of the H2O2-HBr-ethylene glycol system

Equal-etching-rate surfaces for single-crystalline CdTe and Cd_1-x Zn _x Te solid solution samples in etching mixtures of the H₂O₂-HBr-ethylene glycol (EG) system are mapped under reproducible hydrodynamic conditions using simplex design. The dissolution rate laws for these materials are studied, and the concentration boundaries of existence for polishing and nonpolishing solutions are determined. The increasing zinc concentration in the Cd_1-x Zn_xTe solid solution increases the etching rates, while the concentration boundaries of the polishing solutions in the diagram do not change significantly.     

Phase Relationships in the Section CaGeO3-BaSiO3 of the Ternary Mutual System CaO, BaO∥SiO2, GeO2

Phase relationships in the section CaGeO₃-BaSiO₃ in the range 1000-1500°C were studied. Samples were prepared by a solid-phase procedure. The phase relationships were studied by X-ray phase, differential thermal, and crystal-optical (with immersion specimens) analyses and by the annealing-quenching technique. The phase diagram of the system CaGeO₃-BaSiO₃ was constructred. A discrete variable-composition berthollide phase crystallizing in the walstromite structural type was revealed. No solid solutions based on the extreme members of the system were found. The diagram of phase equilibria in the edge sections of the concentration tetragon CaSiO₃-4CaGeO₃-BaGeO₃-BaSiO₃ is presented, and the solubility boundaries are schematically shown for the solid solutions existing in this system at 1200°C.     

Potassium-conducting solid electrolytes in K<Subscript>1 − 2<Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>GaO<Subscript>2</Subscript> system

New solid electrolytes with a high conductivity by K⁺ ions in the K_{1 − 2x} Sr _x GaO₂ system are synthesized and studied. It is found that the introduction of Sr²⁺ ions into potassium monogallate leads to the formation of solid solutions with KGaO₂ structure in a wide range of additive concentration. These solid solutions exhibit a high conductivity; the conductivity increases monotonically with increasing concentration of strontium within the single-phase range. The electrical characteristics are related to the electrolyte structure. The results are compared with the earlier data for the gallate solid electrolytes with the additives of four-charged cations and the systems based on potassium monoferrite and monoaluminate.     

Hexagonal Si−Ge Class of Semiconducting Alloys Prepared by Using Pressure and Temperature

Multi-anvil and laser-heated diamond anvil methods have been used to subject Ge and Si mixtures to pressures and temperatures of between 12 and 17 GPa and 1500–1800 K, respectively. Synchrotron angle dispersive X-ray diffraction, precession electron diffraction and chemical analysis using electron microscopy, reveal recovery at ambient pressure of hexagonal Ge−Si solid solutions (P6₃/mmc). Taken together, the multi-anvil and diamond anvil results reveal that hexagonal solid solutions can be prepared for all Ge−Si compositions. This hexagonal class of solid solutions constitutes a significant expansion of the bulk Ge−Si solid solution family, and is of interest for optoelectronic applications.     

Phase formation and physicochemical properties of perovskite complex oxides based on bismuth ferrite

The effect of the cationic composition on the formation of perovskite solid solutions based on bismuth ferrite(Bi_{1 − x/3}□ _x/3)[Fe_{1 − x} Ti _x ]O₃ with x = 0.00–0.48, Δx = 0.03, has been studied. The homogeneity range of the perovskite phase under the conditions of the solid-phase synthesis of solid solutions has been determined, and the effect of the cationic composition on the physicochemical properties of solid solutions has been studied.     

X-Ray Spectra and Electronic Structure of 3C SiC and BN Based Solid Solutions

The local coherent potential approximation is used in the framework of multiple-scattering theory to calculate the electronic energy structure of solid solutions of silicon carbide Si_1-xCR_x and boron nitride BN_1-xR_x and B_1-xNR_x (x = 0-0.75, R = C, Al, Ti) in a diamond-like modification. The total and partial densities of states are calculated for each atom in the solid solutions. The crystal potential is evaluated in an MT approximation. The lattice parameter is determined by Vegard's rule. The electronic energy structures of the solid solutions are compared with each other and with binary analogs in the framework of one approximation. The calculated partial densities of states are compared with the experimental X-ray spectra of silicon in the compounds. The calculation of the partial charges of atoms at the top of the valence band showed that the charge transfer (0.35 e) from boron to nitrogen in binary 3C BN changes sign in B_0.75NC_0.25. In the latter system, nitrogen donates 0.19 e to boron, and carbon acts as a donor for the electronic configurations of boron and nitrogen. An electronic structure analysis of the solid solutions indicates that the quasicore resonance states inherent in the binary compounds are delocalized, probably because of the weakening of chemical binding in the solid solutions.     

Facile One-step Synthesis of Zn1–xMnxSiN2 Nitride Semiconductor Solid Solutions via Solid-state Metathesis Reaction

We report on the synthesis of the II-IV-N₂ semiconductors ZnSiN₂, MnSiN₂, and the Zn_1–xMn_xSiN₂ solid solutions by a one-step solid-state metathesis reaction. The successful syntheses were carried out by reacting the corresponding metal halides with stoichiometric amounts of silicon nitride and lithium azide in sealed tantalum ampoules. After washing out the reaction byproduct LiCl, powder X-ray diffraction patterns were indexed with orthorhombic space group Pna2₁. Single phase products were obtained without applying external pressure and at a moderate reaction temperature of 700 °C. The resulting ZnSiN₂ was found to consist of nano-sized grains and needle-shaped nano-crystals. With increasing manganese content in the Zn_1–xMn_xSiN₂ solid solution, we found the reaction product to be increasingly crystalline. Both the cell parameters and the bandgap values across the different compositions of the solid solutions change linearly. The sample Zn_0.95Mn_0.05SiN₂ synthesized by means of solid-state metathesis reaction is an intense red emitter with a broad emission maximum at λ_max ≈ 619 nm when excited with ultraviolet light after annealing the sample at a pressure of 6 GPa and a temperature of 1200 °C.     

Determining the boundaries of second-type phase transitions in Ag–Mg–Cd alloys by means of diffusion couples

The interaction between elements in the transition zones of diffusion couples Mg + AgCd–alloy are studied. Isothermal sections of the Ag–Mg–Cd ternary system at 573 K are constructed. The existence of a Heusler phase based on H–Ag₂MgCd compound is found in the field of the solid β′-solution. It is shown that the interdiffusion of components prevents the formation of ordered phases in the transition zones of bimetals, allowing us to determine the boundaries of second-type phase transitions in solid solutions.     

Ionic conduction of Li<Subscript>8 − 2<Emphasis Type="Italic">x</Emphasis></Subscript>Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>ZrO<Subscript>6</Subscript> solid solutions

A boundary of existence of solid solutions in the Li_8−2x Mg _x ZrO₆ system is found to be 7 mol % MgO. The transport properties of Li_{8 − 2x} Mg _x ZrO₆ solid solutions (the electronic component of total conductivity, the temperature and concentration dependences of conductivity and activation energy) are studied. It is supposed that, for Li₈ZrO₆ phase and solid solution based on it, an abrupt change of conductivity in the temperature range from 663 to 713 K is caused by the transition of electrolyte into the superionic state.