Continuous Series Of Mixed Crystals Research Articles

Optimizing Thermoelectric Performance of Hybrid Crystals Bi2O2Se1-xTex in the Bi2O2X System.

In addressing the global need for sustainable energy conversion, this study presents a breakthrough in thermoelectric materials research by optimizing the Bi2O2Se1-xTex system in the Bi2O2Se/Bi2O2Te pseudobinary series. Leveraging the principles of innovative transport mechanisms and defect engineering, we introduce tellurium (Te) doping into Bi2O2Se to enhance its thermoelectric properties synergistically. With the help of various advanced characterization tools such as XRD, SEM, TEM, XPS, FTIR, TGA, LFA, and DSC, combined with relevant resistance and density measurement techniques, we conducted an in-depth exploration of the complex interactions between various factors within thermoelectric materials. We recognize that the balance and synergy of these factors in the thermoelectric conversion process are crucial to achieving efficient energy conversion. Through systematic research, we are committed to revealing the mechanisms of these interactions and providing a solid scientific foundation for the optimal design and performance enhancement of thermoelectric materials. Finally, the advantage coefficient (ZT) of the thermoelectric material has been significantly improved. The crystallographic analysis confirms the formation of a continuous series of mixed crystals with varying Te concentrations, adhering to Vegard's law and exhibiting significant improvements in electrical and thermal conductivities. The Bi2O2Se1-xTex crystals, particularly the Bi2O2Se0.6Te0.4 composition, demonstrate a peak ZT of 0.86 at 373 K. This achievement aligns with recent advancements in defect-enabled mechanisms and band convergence and sets a new standard for high-performance thermoelectrics. The study's findings contribute significantly to the ongoing quest for efficient thermal-to-electrical energy conversion, offering a promising avenue for future sustainable energy technologies.

The Two-Component System CCl4 + CBrCl3. Inference of the Lattice Symmetry of Phase II of CBrCl3

The phase diagram of the two-component system between two halomethanes, carbon tetrachloride (CCl4) and bromotrichloromethane (CBrCl3) has been determined by means of X-ray powder diffraction and thermal analysis techniques from 200 K to the liquid state. From the continuous series of mixed crystals, three relations of isomorphism have been evidenced: (i) between the stable low-temperature monoclinic (M) phases, (ii) between the stable orientationally disordered (OD) rhombohedral (R) phases, and (iii) between the stable OD face-centered cubic (FCC) of CBrCl3 and the metastable FCC phase of CCl4. The existence of such a metastable phase gives rise to the appearance, for a large range of composition, of metastable FCC mixed crystals that behave monotropically with respect to the R mixed crystals accordingly with the well-known monotropic character of the R to FCC phase transition of the CCl4. The isomorphism relationships i and ii enable us to validate the previously proposed structure of the monoclinic ph...

Multiple melting of orientationally disordered mixed crystals of the two-component system (CH3)2CCl2–(CH3)CCl3

Orientationally disordered (OD) stable and metastable mixed crystals of the two-component system 2,2-dichloropropane ((CH3)2CCl2)+methylchloroform ((CH3)CCl3) have been characterized from crystallographic and thermodynamic points of view. Continuous series of mixed crystals in the stable rhombohedral (R) phase points out an isomorphism relationship. The monotropic behavior of the non-isomorphous OD metastable phases in the pure components (simple cubic, SC, and face-centered cubic, FCC, respectively) with respect to the R stable phase is partially retained by the mixed crystals. In particular, SC mixed crystals were found persistent enough as metastable crystals in the whole composition range with the exception of the pure compound (CH3)CCl3, for which only the FCC metastable phase was experimentally available. On the contrary, samples with compositions greater than X=0.70 in (CH3)CCl3 crystallized into either the FCC or SC, both being metastable with respect to the R phase. Thus, three kinds of OD mixed crystals appear which give rise to three independent OD+Liquid equilibria. The thermodynamic analysis of such non-interfering equilibria, [R+L], [SC+L] and [FCC+L], enables us to infer the stability relationships between the whole of OD phases.

Crystallographic Evidence for the Formation of a Continuous Series of Mixed Crystals between NiO and LiNiO2

The system NiO − Li1-xNi1+xO2, with 0 ≤ x ≤ 1 has to be considered as a continuous series of mixed crystals of one structure type (structure of α-NaFeO2). The substitution of one Ni2+ ion in NiO by a Li+ ion is accompanied by the oxidation of another Ni2+ ion to Ni3+. In the series NiO − Li1-xNi1+xO2 the Vegard rule holds true for both lattice constants “a” and “c”. The literature statements on the formation of different phases in the system NiO − Li1-xNi1+xO2 are obviously misinterpretations of the X-ray data. A very simple low-temperature solution combustion technique was adopted in this study to prepare different samples of this mixed crystal series. The samples were characterized by inductively coupled plasma for elemental analysis and by X-ray powder diffraction and Rietveld refinement for structural analysis.

Polymorphism of racemic felodipine and the unusual series of solid solutions in the binary system of its enantiomers

The aim of this study was to investigate the binary phase diagram and the polymorphism and pseudopolymorphism of racemic and enantiomeric felodipine, including their spectroscopic and thermodynamic properties. Different crystal forms were obtained by crystallization from solvents or from the annealed melt and investigated by thermal analysis (hot stage microscopy, differential scanning calorimetry, thermogravimetric analysis), spectroscopic methods (Fourier transform infrared–and Fourier transform–Raman spectroscopy), and X-ray powder diffractometry. The binary melting phase diagram was constructed based on thermoanalytical investigations of quantitative mixtures of (+)- and (±)-felodipine. Two polymorphic forms of racemic felodipine, mod. I (mp, ∼145°C) and mod. II (mp, ∼135°C), as well as an acetone solvate (SAc ) were characterized. Melting equilibria of felodipine crystal forms decrease due to thermal decomposition. Enantiomeric felodipine was found to be dimorphic (En-mod. I: mp, ∼144°C; En-mod. II: mp, ∼133°C). Evaluation of the binary system of (+)- and (−)-felodipine results in the formation of a continuous series of mixed crystals between the thermodynamically stable and higher melting modifications, mod. I and En-mod. I. Their unusual curve course, termed as Roozeboom Type 2 b, passes through a maximum in the racemic mixture and is flanked by a minimum at 20% and at 80% (+)-felodipine. From the thermodynamic parameters, racemic mod. I and II are monotropically related. In contrast to SAc, the thermodynamically unstable mod. II shows a considerable kinetic stability. Because its crystallization is badly reproducible, the use of mod. II is not advisable for processing. However, desolvation of SAc leads to a profitable crystal shape of mod. I, representing a pseudoracemate by definition. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:949–959, 2001

Stable and metastable orientationally disordered mixed crystals of the two-component system (CH 3) 2CCl 2+CCl 4

Orientationally disordered stable and metastable mixed crystals of the two-component system 2,2-dichloropropane ((CH 3) 2CCl 2)+carbon tetrachloride (CCl 4) have been characterised from crystallographic and thermodynamic points of view. The monotropic behaviour of the metastable phases in the pure components is retained by the mixed crystals. Continuous series of mixed crystals in the stable rhombohedral phase gives rise to an isomorphism relationship. The lattice symmetries of the metastable mixed crystals are found to be simple cubic and face centred cubic, the latter corresponding to a large concentration domain. A strong correlation between thermodynamic functions and optical properties is proposed.

Isomorphic relationship between 1,2,4,5-tetrachlorobenzene and 1,2,4,5-tetrabromobenzene

1,2,4,5-Tetrachlorobenzene (TeCB) exhibits a phase transition α → β at 185 K whereas 1,2,4,5-tetrabromobenzene (TeBB) exhibits a phase transition β→ γ at 307 K, the `room temperature' form being β for the two compounds. This work establishes which are the isomorphous forms. Quenching the molten mixtures into liquid nitrogen produced molecular alloys (TeCB)1 − x(TeBB)x at 295 K with any value of x, even in the 0.20 ≤ x ≤ 0.75 and 0.81 ≤ x ≤ 0.97 ranges where these molecular alloys are only metastable because of demixing phenomena. Powder diffraction analysis on the whole range of molecular alloys proved that βTeCB is isomorphous in the strictest sense (i.e. capable of giving a continuous series of mixed crystals) with the γ form of TeBB.

Thermodynamic study of the co-crystallization of 2RbCl·NiCl 2·2H 2O and 2RbCl·MnCl 2·2H 2O, at the temperature 298.15 K

The molalities mof ( m 12RbCl·NiCl 2·2H 2O + m 22RbCl·MnCl 2·2H 2O)(aq) have been investigated at the temperature T= 298.15 K and formation of a continuous series of mixed crystals has been found. On the basis of the present and earlier experimental data it has been established that the formation of a continuous mixed crystal series of isostructural double salts 2MCl·MeCl 2·2H 2O depends on the close values of the unit cell parameters. The basic Pitzer ion-interaction model has been used for the first time or determining the thermodynamic characteristics of the formation process of mixed crystals of double salts. The component activities of the saturated ternary solution ( m 12RbCl·NiCl 2·2H 2O + m 22RbCl·MnCl 2·2H 2O)(aq) and in the mixed crystalline phase are determined and the change of the molar Gibbs energy of mixing Δ mix G mof crystals is determined depending on the solid phase composition given in mole fractions. It is established that at T= 298.15 K the mixed 2RbCl·(Ni, Mn)Cl 2·2H 2O crystals show positive deviations from the ideal mixed crystals. Using the regular mixing model, the results obtained can be summarized by the following equation: Δ mix G m= − x 1, x 2·(3.30 ± 0.50) kJ·mol −1.

Laevorotatory-carvoxime + dextrorotatory-carvoxime a unique binary system

The system laevorotatory-carvoxime + dextrorotatory-carvoxime displays unique thermodynamical and structural properties. Its solid-liquid phase diagram, having a maximum, suggests a continuous series of mixed crystals of the disordered substitutional type. The maximum, however, corresponds to an ordered structure. On the basis of phase diagram and thermochemical data a macroscopic thermodynamic description of the system is presented.

Crystal chemistry of the salts Me+Cl · Me2+Cl2 · 2 H2O

AbstractThe crystal chemistry of the double salts Me+Cl · Me2+Cl2 · 2 H2O (where (Me+ = K, Rb, Cs; Me2+ = Mn, Fe, Co, Ni) is considered. It is concluded that these salts crystallize in three types of structures, the Me+ ion size being decisive for the structure type.Salts containing the large Cs+ ions crystallize in an orthorhombic structure in which [Me2+ (H2O)2Cl4] octahedra form chains having common Cl− corners.Salts with the smaller K+ ions crystallize in a tricline system, the [Me2+ (H2O)2Cl4] octahedra being connected by a common Cl–Cl edge and forming dimers.When the intermediate in size Rb+ ions are present in the salts, either of the above structures is possible as well as a monoclinic structure which is intermediate in symmetry.The expected isostructure of the cesium salts was checked by studing the CsCl · NiCl2 · 2 H2O–CsCl · MnCl2 · 2H2O–H2O system. A continuous series of mixed crystals is found.

Isomorphic Co-Crystallization of Ammonium and Rubidium Bromocarnallites

The solubility isotherm of the system NH4Br.MgBr2.6 H2O - RbBr.MgBr2.6 H2O - H2O has been investigated at 75 °C and formation of a continuous series of mixed crystals is established. The factors determining the values of the distribution coefficients of the components between the crystalline and liquid phases are discussed.

Solid-liquid equilibria in the fifteen binary systems shared by the six isomeric tribromotoluenes homage to F.M. Jaeger

A thermodynamic analysis is presented of the isobaric binary solid-liquid equilibria in the fifteen binary systems shared by the six isomeric tribromotoluenes. Eleven of the systems are eutectic, one system is an example of a system with a continuous series of mixed crystals and a phase diagram with a maximum and three systems are examples of crossed isodimorphism. The experimental data are from a paper published in 1904 by F.M. Jaeger.

Co‐Crystallization in systems with carnallite‐type double salts

AbstractThe RbCl · MgCl2 · 6H2ONH4Cl · MgCl2 · 6H2OH2O and CsCl · MgCl2 · 6H2ONH4Cl · MgCl2 · 6H2OH2O systems have been investigated at 50°C. The formation of continuous series of mixed crystals is observed. An almost complete coincidence of the distribution coefficients values of the components between the solid and liquid phases determined experimentally and calculated theoretically using only solubility data for the two double salts has been established.The 2 RbCl · CoCl2 · 2H2ORbCl · MgCl2 · 6H2OH2O system has been studied at 25°C. It has been established that this system belongs to the simple eutonic type. The two double salts form no mixed crystals between each other. This fact is explained by the different character of the metal‐ligand interaction of Mg2+ and Co2+ ions in aqueous halide systems.

Cation distribution in Cu xCd 1− x(HCOO) 2 · 2H 2O mixed crystals

It was established that Cu(HCOO) 2 · 2H 2O and Cd(HCOO) 2 · 2H 2O form a continuous series of mixed crystals. The nonlinear dependence of the lattice parameters of the Cu x Cd 1− x (HCOO) 2 · 2H 2O mixed crystals on the composition and the observed shift of the absorption maximum in the visible range at x > 0.5 are explained well by the preferential occupation of the two available lattice sites by the copper ions. The shift of the absorption maximum at x > 0.5 toward the higher energy is evidence in favor of the hypothesis that the copper ions prefer a mixed coordination environment.

The phase diagram of magnesium bromide and chloride hexahydrate mixtures

The liquidus of the phase diagram of MgCl 2·6 H 2O+MgBr 2·6 H 2O mixtures was determined, and a continuous series of mixed crystals was found to be formed on freezing. The freezing point of MgBr 2 · 6 H 2O was confirmed to be 164.4±0.3°C, but on repeated melting—freezing cycles this value decreased, due to loss of water. An approximate value of the specific heat of fusion of MgBr 2 · 6 H 2O, of 150 J g −1, was determined.

Charge-density-waves of variable incommensurability in the system TaTe 4  NbTe 4

It was reported previously that the isostructural quasi-one-dimensional crystals TaTe 4 and NbTe 4 contain CDW at room temperature and that the CDW in the former is commensurate with the parent lattice while that in the latter is strongly incommensurate. It is shown that a continuous series of mixed-crystals (Nb 1−xTa x)Te 4 (0 ≤ x ≤1) can be prepared and tht the q-vectors of the distortion waves in these crystals vary linearly with x. The possibility of using this system to test structural models of the incommensurate CDW is discussed and limitations imposed by current experimental problems are noted.

Preparation and properties of mixed crystals SnS (1−x)Se x

SnS and SnSe were purified by distillation. Single crystals grown from the purified material contained less than 2.5 × 10 16 cm −3 impurities (spectrochemical analysis). The solid-liquid equilibrium SnS-SnSe was determined. It was found that the two compounds form a continuous series of mixed crystals, with a minimum melting point of 853°C at a composition SnS 0.5Se 0.5. The S and Se atoms in the mixed crystals are randomly distributed. The dimensions of the crystallographic unit cell of mixed crystals SnS 1− x Se x vary linearly with the composition x. The crystals were all p-type with p ∼ 10 18 cm −3. At 300°K, the mobility perpendicular to the c-axis as a function of the composition shows a single minimum of 65 cm 2/V sec for SnS 0.7Se 0.3, the corresponding values for SnS and SnSe being respectively 90 and 115. The mobility varies approximately with T −2, indicating lattice scattering. For all crystals the band-edge absorption was found to be due to allowed indirect transitions. The bandgap of SnS and SnSe at 300°K is 1.08 and 0.90 eV respectively. The bandgap of mixed crystals SnS (1− x) Se x varies linearly with x.

579. Solid transitions in mixed crystals of ethylene dichloride and ethylene dibromide

INTRODUCTION In principle, the heat capacity curve of a solid substance can give information about the dependence of energy absorption on temperature of the crystal lattice, and hence on the mechanism of any phase changes which occur therein. In practice, however, the amount of information is limited (a) by the fact that a considerable contribution to the measured Cp comes from the term f32VTja; (b) by the lack of an adequate theory of the heat capacities of complex crystals. In certain cases, though, considerable insight can be obtained by diluting the lattice of a compound which undergoes a phase transition with a second kind of molecule or ion, and observing the effect on the nature and magnitude of the transition. The added component has usually been one which itself has no transitions', but a few studies have been made of mixed crystals both of whose components exhibit solid transitions2, when the phenomena are naturally more complex. This paper concerns heat capacity measurements on mixtures of ethylene dichloride and dibromide, both of which undergo solid transitions, and form a continuous series of mixed crystals.

On the spontaneous crystallisation and the melting- and freezing-point curves of two substances which form mixed crystals and whose freezing-point curve exhibits a transition point. -Mixtures of p -bromnitrobenzene and p -chlornitrobenzene

The following paper is a continuation of two previous papers in which the melting- and freezing-point curves for two pairs of substances, each of which forms mixed crystals, have already been determined. In the first of these papers mixtures of naphthalene and β -naphthol were examined and found to a form a continuous series of mixed crystals and to give curves of Roozeboom's Type I, in which the melting and freezing points of all mixtures lie between the melting points of the pure substances.

A spectro-photometric comparsion of the emissivity of solid liquid copper and of liquid silver at high temperatures with that of a full radiator

The following paper is a continuation of two previous papers in which the melting- and freezing-point curves for two pairs of substances, each of which forms mixed crystals, have already been determined. In the first of these papers* mixtures of naphthalene and β -naphthol were examined and found to form a continuous series of mixed crystals and to give curves of Roozeboom’s Type I, in which the melting points of the pure substances.