Complete Series Of Solid Solutions Research Articles

Crystal Growth, composition, structure, and Raman spectroscopy of novel Ga,Ge-rich topaz

Single crystals of Ga-, Ge-, and Ga,Ge-rich (up to 41.42 wt% GeO2 and 33.95 wt% Ga2O3 or 0.98 apfu (atom per formula unit) Ge and 0.90 apfu Ga) and undoped topazes were grown on natural topaz seeds as a newly overgrown layer up to 5 mm thick. The thermogradient hydrothermal method was used at a temperature range of 600 − 650 °C and a pressure of 100 MPa under the condition of reverse temperature solubility factor of silica and alumina in the fluoride solution. The chemical composition and crystal structure of the grown topazes, as well as the distribution of gallium and germanium in the overgrown layer, were investigated by electron microprobe analysis (EMPA), single crystal X-ray diffraction (SCXRD) and Raman spectroscopy. The overgrown layers of Ge-, and Ga,Ge-rich topazes have a zonal distribution of elements, two zones corresponding to topaz Al2SiO4(F,OH)2 and krieselite (Al,Ga)2GeO4(F,OH)2 compositions are distinguished. The structural and spectroscopic studies show linear dependences of unit cell parameters and Raman shift on germanium and gallium contents and confirm the existence of a complete series of topaz-krieselite solid solution.

The effect of chemical variability and weathering on Raman spectra of enargite and fahlore

Abstract. Enargite (Cu3AsS4) and tennantite (Cu12As4S13) are typical As-bearing sulfides in intermediate- and high-sulfidation epithermal deposits. Trace and major element variations in enargite and tennantite and their substitution mechanisms are widely described. However, Raman spectra of the minerals with correlative quantitative chemical information are rarely documented, especially for enargite. Therefore, comparative electron and μ-Raman microprobe analyses were performed on enargite and fahlore grains. These spectra can be used in the industrial detection and subsequent removal of As-bearing sulfides prior to ore beneficiation in order to diminish the environmental impact of the metallurgical technologies. A simple Sb5+–As5+ substitution in enargite was confirmed by Raman analyses. Similarly, a complete solid solution series from tetrahedrite to tennantite (i.e., Sb3+–As3+ substitution) can be correlated with a gradual evolution in their Raman spectra. In turn, Te4+ occupies the As3+ and Sb3+ sites in fahlore by the coupled substitution Te4+ + Cu+ → (As, Sb)3+ + (Cu, Fe, Zn)2+. Accordingly, Raman bands of goldfieldite (Te-rich member) are strongly broadened compared with those of tetrahedrite and tennantite. A secondary phase with high porosity and a fibrous or wormlike texture was found in enargite in a weathered sample. The chemical composition, Raman spectrum, and X-ray diffraction signature of the secondary phase resemble tennantite. A gradual transformation of the primary enargite into this secondary phase was visualized by comparative electron and Raman microprobe mapping.

Sol-Gel-Syntheses and Structural as well as Electrical Characterizations of Anatase- and Rutile-Type Solid Solutions in the System IrO2 -TiO2.

This paper describes solid solutions in the quasibinary oxide system iridium-titanium IrO2 -TiO2 with rutile and anatase crystal structures. Based on X-ray diffraction evaluations using Rietveld refinements, changes of lattice parameters were determined within the composition series of 0-100 mol % iridium. These changes prove the existence of a complete solid solution series in the rutile structure type. The solubility limit for iridium in the anatase lattice was found to be 6.0(8) mol % iridium for the underlying sol-gel process. In addition, iridium is a promoter for the conversion from anatase to rutile type. Furthermore, the X-ray diffraction results of a calcination temperature series for the composition with 5 mol % iridium are shown, which confirm the findings of the composition series and allow conclusions on the phase segregation behavior. The results are complemented by 2-point conductivity measurements at different pressures in a piston press to investigate the question of the conductivity mechanism.

On the matildite–bohdanowiczite solid-solution series

AbstractA high-grade ore sample from the Cu–Zn–Au Photo Lake volcanogenic massive sulfide deposit (Flin Flon–Snow Lake greenstone belt, Manitoba, Canada) contains a Bi–Ag sulfo-selenide with a composition situated approximately in the middle of the S–Se substitution range (Se ≈ 0.86 apfu and S ≈ 1.05 apfu). These new data, combined with a literature compilation of all publicly available matildite and bohdanowiczite compositional data, reveal a nearly complete range of S–Se substitution between these two minerals, with only the section between BiAgSe0.78S1.18 and BiAgSe0.25S1.75 – about a quarter of the complete S–Se range – not yet documented. These observations suggest that a complete solid-solution series between matildite and bohdanowiczite, as previously suspected, might exist and in a manner similar to the galena–clausthalite complete solid-solution series.

Dissolution and solubility of calcite-rhodochrosite solid solutions [(Ca1-xMnx)CO3] at 25\xa0\xb0C

A complete series of calcite-rhodochrosite solid solutions [(Ca1-xMnx)CO3] are prepared, and their dissolution processes in various water samples are experimentally investigated. The crystal morphologies of the solid solutions vary from blocky spherical crystal aggregates to smaller spheres with an increasing incorporation of Mn in the solids. Regarding dissolution in N2-degassed water, air-saturated water and CO2-saturated water at 25 °C, the aqueous Ca and Mn concentrations reach their highest values after 1240–2400 h, 6–12 h and < 1 h, respectively, and then decrease gradually to a steady state; additionally, the ion activity products (log_IAP) at the final steady state (≈ solubility products in log_Ksp) are estimated to be − 8.46 ± 0.06, − 8.44 ± 0.10 and − 8.59 ± 0.10 for calcite [CaCO3], respectively, and − 10.25 ± 0.08, − 10.26 ± 0.10 and − 10.28 ± 0.03, for rhodochrosite [MnCO3], respectively. As XMn increases, the log_IAP values decrease from − 8.44 ~ − 8.59 for calcite to − 10.25 ~ − 10.28 for rhodochrosite. The aqueous Mn concentrations increase with an increasing Mn/(Ca + Mn) molar ratio (XMn) of the (Ca1-xMnx)CO3 solid solutions, while the aqueous Ca concentrations show the highest values at XMn = 0.53–0.63. In the constructed Lippmann diagram of subregular (Ca1-xMnx)CO3 solid solutions, the solids dissolve incongruently, and the data points of the aqueous solutions move progressively up to the Lippmann solutus curve and then along the solutus curve or saturation curve of pure MnCO3 to the Mn-poor side. The microcrystalline cores of the spherical crystal aggregates are preferentially dissolved to form core hollows while simultaneously precipitating Mn-rich hexagonal prisms.

Fahlore and Sphalerite from the Darasun Gold Deposit in the Eastern Transbaikal Region, Russia: I. Mineral Assemblages and Intergrowths, Chemical Composition, and Its Evolution

The mineral assemblages, mode of occurrence, and chemical compositions of coexisting fahlore and sphalerite from the Darasun gold deposit have been described. Three generations of fahlore and three generations of sphalerite have been recognized. The FeS content in sphalerite coexisting with fahlore ranges from 0.8 to 9.4 mol %. The complete solid solution series Fe-tetrahedrite–Zn-tetrahedrite–Fe-tennantite–Zn-tennantite reflected in Sb/(Sb + As) and Fe/(Fe + Zn) ratios ranging from 0 to 0.97 and from 0.07 to 1.00, respectively, with a predominant negative relationship between these ratios has been identified for the first time at the deposit. Stepped, oscillatory, and combined stepped-oscillatory growth zonings within fahlore grains and heterogeneous aggregates of fahlore have been found. Fahlore is enriched in As with respect to Sb, and Zn-tetrahedrite is followed by Fe- and Zn-tennantite from early to late generation; Zn-tetrahedrite is followed by Fe-tennantite in zoned grains and overgrown rims; sphalerite crystallized at decreased temperature and sulfur fugacity. The evolution of the chemical composition of fahlores was caused by the evolving temperature, fluid salinity, and conditions of metal migration.

Structural and Raman spectroscopic characterization of pyroxene-type compounds in the CaCu1-xZnxGe2O6 solid-solution series.

Pyroxene-type germanate compounds with the composition CaCuGe2O6-CaZnGe2O6 have been synthesized via a solid-state ceramic sintering route. Phase-pure polycrystalline and small single-crystal material was obtained all over the series, representing a complete solid-solution series. Differential thermal analysis, single-crystal X-ray diffraction and Raman spectroscopy were used to characterize phase stability, phase changes and structural alterations induced by the substitution of Cu2+ with Zn2+. Whereas pure CaCuGe2O6 exhibits P21/c symmetry with a strong distortion of the M1 octahedra and two different Ge sites, one of them with an unusual fivefold coordination, the replacement of Cu2+ by Zn2+ induces a chemically driven phase change to the C2/c symmetry. The phase change takes place around Zn2+ contents of 0.12 formula units and is associated with large changes in the unit-cell parameters. Here, the increase of c by as much as 3.2% is remarkable and it is mainly controlled by an expansion of the tetrahedral chains. Further differences between the P21/c and C2/c structures are a more regular chain of edge-sharing M1 octahedra as a consequence of more and more reduced Jahn-Teller distortion and a less kinked, symmetry-equivalent tetrahedral chain. The coordination of the Ca site increases from sevenfold to eightfold with large changes in the Ca-O bond lengths during the phase change. Raman spectroscopy was mainly used to monitor the P21/c to C2/c phase change as a function of composition, but also as a function of temperature and to follow changes in specific Raman modes throughout the solid-solution series.

Ionic Mixed Hydride Fluoride Compounds: Stabilities Predicted by DFT, Synthesis, and Luminescence of Divalent Europium

The hydride fluoride solid solution series LiSrH3–xFx, LiBaH3–xFx, KMgH3–xFx, and EAH2–xFx (EA = Ca, Sr, Ba) was studied by first-principle calculations, and luminescence of SrH0.5F1.5:Eu2+ and KMgHF2:Eu2+ was observed. Theoretical calculations suggest the existence of a complete solid solution series in the case of LiBaH3–xFx and KMgH3–xFx, whereas only a partial solid solution series for the hydrogen-rich side is predicted for LiSrH3–xFx. For the luminescence of divalent europium in SrH0.5F1.5 an emission maximum at 600 nm is observed, which lies in between the emission wavelength of the pure hydride (728 nm) and fluoride (416 nm). Likewise, the emission maximum of Eu2+ in KMgHF2 was found to be ∼505 nm, which corresponds to a blue shift relative to the hydride (565 nm) and a strong red shift compared with the fluoride (363 nm and ff emission). Consequently, substitution of hydride and fluoride shows a strong influence on the europium d levels due to the different polarizabilities.

Thermodynamics of arsenates, selenites, and sulfates in the oxidation zone of sulfide ores. X. thermal stability and dehydration features of synthetic analogs of the cobaltomenite–ahlfeldite solid solution series

The aim of this study is the experimental investigation of the synthetic analogs of cobaltomenite, CoSeO3 • 2H2O, ahlfeldite, NiSeO3 • 2H2O, members of the cobaltomenite–ahlfeldite solid solution series (NixCo1–x)SeO3 • 2H2O, and singularities of their dehydration and dissociation. The intermediate members of the cobaltomenite (CoSeO3 • 2H2O)–ahlfeldite (NiSeO3 • 2H2O) series have been synthesized and studied with a combination of X-ray diffraction, scanning electron microscopy, and the simultaneous application of thermogravimetry (TG) and differential scanning calorimetry (DSC) within the temperature range from 25 to 640°C. The complete solid solution series corresponds to the monoclinic space group P21/n. Unit-cell dimensions decrease in all crystallographic directions as the amount of Ni increases. The angle β increases from 98.82(1) (cobaltomenite) to 99.05(1)° (ahlfeldite). It has been established that CoSeO3 • 2H2O and NiSeO3 • 2H2O dehydrate at 120–340°C through two stages apparently corresponding, to the formation of intermediate hydrated species CoSeO3 • H2O and NiSeO3 • 1/3H2O. The reaction enthalpies for each dehydration stage of CoSeO3 • 2H2O and NiSeO3 • 2H2O have been determined. Changes of the unit-cell dimensions and dehydration temperatures are rationalized in terms of the Co and Ni site occupancy in the structure of the cobaltomenite–ahlfeldite solid-solution series members.

A Complete Solid Solution with Rutile‐Type Structure in SiO2–GeO2 System at 12 GPa and 1600°C

High pressure and temperature synthesis of compositions made of (Si1−x,Gex)O2 where x is equal to 0, 0.1, 0.2, 0.5, 0.7, and 1 was performed at 7–12 GPa and 1200–1600°C using a Kawai‐type high‐pressure apparatus. At 12 GPa and 1600°C, all the run products were composed of a single phase with a rutile structure. The lattice constants increase linearly with the germanium content (x), which indicates that the rutile‐type phases in the SiO2–GeO2 system form a complete series of solid solutions at these pressure and temperature conditions. Our experimental results show that thermodynamic equilibrium state was achieved in this system at 12 GPa and 1600°C, but not at 1200°C. At lower pressures (7 and 9 GPa) and 1600°C, we observed the decomposition of (Si0.5,Ge0.5)O2 into SiO2‐rich coesite and GeO2‐rich rutile phases. The silicon content in the rutile structure increases sharply with pressure in the vicinity of the coesite–stishovite phase transition pressure in SiO2.

ChemInform Abstract: A Solid Solution Series of Atacamite Type Ni2xMg2—2xCl(OH)3.

AbstractA complete solid solution series of Ni2xMg2‐2xCl(OH)3 from Mg2Cl(OH)3 and Ni2Cl(OH)3 is prepared under hydrothermal conditions using aqueous solutions of Mg(OH)2, MgCl2, Ni(OH)2, and NiCl2 (TiPd autoclave, 200 °C, up to 2 months).

ChemInform Abstract: Synthesis and Characterization of the LiMnBO3—LiCoBO3 Solid Solution and Its Use as a Lithium‐Ion Cathode Material.

AbstractThe complete solid solution series of monoclinic Li(Mn1‐xCox)BO3 (0 ≤ x ≤ 1) is synthesized from mixtures of M3(BO3)2 (M: Mn, Co), Li2CO3, and H3BO3 (Ar atmosphere, 500 °C, 6 h) and characterized by powder XRD, TEM, and electrochemical measurements.

Silver Indium Telluride Semiconductors and Their Solid Solutions with Cadmium Indium Telluride: Structure and Physical Properties.

Ag0.8In2.4Te4 (= AgIn3Te5) and Ag0.5In2.5Te4 (= AgIn5Te8) form solid solutions with CdIn2Te4, which are interesting as materials for photovoltaics or with respect to their thermoelectric properties. The corresponding crystal structures are related to the chalcopyrite type. Rietveld refinements of high-resolution synchrotron powder diffraction data measured at K-absorption edges of Cd, Ag, In, and Te and electron diffraction reveal the symmetry as well as the element and vacancy distribution in Ag0.8In2.4Te4 (= AgIn3Te5)/Ag0.5In2.5Te4 (= AgIn5Te8) mixed crystals such as Ag0.25Cd0.5In2.25Te4 and Ag0.2Cd0.75In2.1Te4. All compounds of the solid solution series (CdIn2Te4)x(Ag0.5In2.5Te4)1-x exhibit the HgCu2I4 structure type (space group I4̅2m) with completely ordered vacancies but disordered cations. The uniform cation distribution and thus the local charge balance are comparable to that of CdIn2Te4. In contrast, Ag0.8In2.4Te4 (= AgIn3Te5) crystallizes in the space group P4̅2c with disordered cations and partially ordered vacancies. This is corroborated by bond-valence sum calculations and the fact that there is a Vegard-like behavior for compounds with 0.5 < x in the pseudobinary system (CdIn2Te4)x(Ag0.8In2.4Te4)1-x. Owing to the different structures, there is no complete solid solution series between CdIn2Te4 and AgIn3Te5. All compounds in this work are n-type semiconductors with a low electrical conductivity (∼1 S/m) and rather high absolute Seebeck coefficients (up to -750 μV/mK; 225 °C). Electrical band gaps (Eg) determined from the Seebeck coefficients as well as (more reliably) from the electrical conductivity range between 0.19 and 1.13 eV.

A solid solution series of atacamite type Ni2xMg2−2xCl(OH)3

For the first time a complete solid solution series Ni2xMg2−2xCl(OH)3 of an atacamite type alkaline main group metal chloride, Mg2Cl(OH)3, and a transition group metal chloride, Ni2Cl(OH)3, was prepared and characterized by chemical and thermal analysis as well as by Raman and IR spectroscopy, and high resolution laboratory X-ray powder diffraction. All members of the solid solution series crystallize in space group Pnam (62). The main building units of these crystal structures are distorted, edge-linked Ni/MgO4Cl2 and Ni/MgO5Cl octahedra. The distribution of Ni2+- and Mg2+-ions among these two metal-sites within the solid solution series is discussed in detail. The crystallization of the solid solution phases occurs via an intermediate solid solution series, (Ni/Mg)Cl2x(OH)2−2x, with variable Cl: OH ratio up to the 1:3 ratio according to the formula Ni2xMg2−2x Cl(OH)3. For one isolated intermediate solid solution member, Ni0.70Mg0.30Cl0.58(OH)1.42, the formation and crystal structure is presented as well.

Effect of Isovalent Substitution on the Thermoelectric Properties of the Cu2ZnGeSe4–xSx Series of Solid Solutions

Knowledge of structure-property relationships is a key feature of materials design. The control of thermal transport has proven to be crucial for the optimization of thermoelectric materials. We report the synthesis, chemical characterization, thermoelectric transport properties, and thermal transport calculations of the complete solid solution series Cu2ZnGeSe(4-x)S(x) (x = 0-4). Throughout the substitution series a continuous Vegard-like behavior of the lattice parameters, bond distances, optical band gap energies, and sound velocities are found, which enables the tuning of these properties adjusting the initial composition. Refinements of the special chalcogen positions revealed a change in bonding angles, resulting in crystallographic strain possibly affecting transport properties. Thermal transport measurements showed a reduction in the room-temperature thermal conductivity of 42% triggered by the introduced disorder. Thermal transport calculations of mass and strain contrast revealed that 34% of the reduction in thermal conductivity is due to the mass contrast only and 8% is due to crystallographic strain.

Thermodynamic properties of solid solutions in the system Ag2S–Ag2Se

We have summarized experimental data on the phase diagram of the system Ag2S–Ag2Se. Standard thermodynamic functions of four solid solutions in this system have been calculated using the model of regular and subregular solutions: a restricted fcc solid solution γ-Ag2S-Ag2S1−xSex (x<0.3, 867<T<1110K) and complete bcc solid solution series along β-Ag2S–Ag2Se, monoclinic solid solution (α) from Ag2S to Ag2S0.4Se0.6, and orthorhombic solid solution (α) from Ag2S0.3Se0.7 to the Ag2Se. Gmix and Smix have been evaluated using the subregular model for asymmetric solution for the region Ag2S0.4Se0.6–Ag2S0.3Se0.7. The thermodynamic data can be used for modeling in complex natural systems and in matters of semiconductor materials.

Synthesis, Characterization, and Chemical Vapor Transport of Solid Solutions in the MgMoO4‐NiMoO4 System

AbstractTwo solid solution series exist in the system MgMoO4‐NiMoO4. The α‐Ni1–yMgyMoO4 solution series, isostructural to α‐NiMoO4, is thermodynamically stable at ambient conditions for compositions between 0 % and about 75 % magnesium content. The solution series β‐Mg1–xNixMoO4, isostructural to MgMoO4 and the high temperature β modification of NiMoO4, is thermodynamically stable at ambient conditions for compositions with &lt; 25 % nickel content. A complete solid solution series β‐Mg1–xNixMoO4 exists at higher temperatures (&gt; 823 K). The transition temperature for the α → β transition decreases with increasing magnesium content. The coexistence of both polymorphs at room temperature in samples with a wide range of composition is a result of the kinetic inhibition of the phase transition β → α. The chemical vapor transport of β‐Mg1–xNixMoO4 solid solutions with chlorine was investigated. Crystals with a nickel content up to 25 % were synthesized in temperature gradients 1273 K → 1223 K or 1273 K → 1173 K. Deposited nickel richer crystals are destroyed during cooling down to room temperature due to the phase transition. The observed distinctive nickel enrichment during the transport process is in good agreement with predictions by thermodynamic modeling.

NACARENIOBSITE-(Ce) AND BRITHOLITE-(Ce) IN PERALKALINE GRANITES FROM THE MORRO REDONDO COMPLEX, GRACIOSA PROVINCE, SOUTHERN BRAZIL: OCCURRENCE AND COMPOSITIONAL DATA

Nacareniobsite-(Ce), Na 3 Ca 3 (REE)Nb(Si 2 O 7 ) 2 OF 3 , and britholite-(Ce), (Na,Ca,REE) 10 (Si,P) 6 O 24 (OH,F) 2 , formed during the late stages of crystallization of the most evolved peralkaline granites from the Morro Redondo Complex, Graciosa Province (Southern Brazil). Nacareniobsite-(Ce) compositions are very close to ideal, with Na 2 O and Nb 2 O 5 contents up to 11.1 and 15.5 wt.%, respectively, corresponding to an average formula of Na 3.0 (Ca 2.75 Sr 0.01 ) ∑2.76 (REE,Y) 1.16 (Nb 0.95 Ta 0.02 Ti 0.04 ) ∑1.01 Si 3.99 O 14 (O 1.11 F 2.89 ) ∑4 . Compared to the host rock composition, trace-element patterns for nacareniobsite-(Ce) indicate enrichment in REEs and Sr, and depletion in alkali metals and Zr. The available chemical data are in excellent agreement with a complete solid solution series between rinkite and nacareniobsite-(Ce), controlled by [M +4 M 2+ ] −1 [M 5+ Na + ] and, in part, [M 2+ ] −2 [REE 3+ Na + ] and [M +4 M 2+ ] −1 [REE 3+ ] 2 exchange vectors. Britholite-(Ce) compositions are amongst the most (REE,Y)-enriched reported to date, with REE + Y contents up to 73.6 wt.% oxide. REE and trace element distributions relative to the host rock exhibit some similarities with those observed for nacareniobsite-(Ce); however, Ba, Th, U, and Pb contents are relatively higher. The observed compositions agree very well with [PM 2+ F] −1 [Si(REE,Y)(OH)], [M 2+ ] −2 [Na(REE,Y)], and [M 2+ (Th,U)] −1 [(REE,Y)] 2 exchange vectors. Crystallization of both minerals was favored by the F-, Na-, and HFSE-enriched nature and moderate-to-strong peralkaline signature of the melt, at temperatures below 600 °C in a relatively reduced environment.

First Principles Study of Copper Sulfides (for Applications as Photoconductors)

The Tetrahedrite’s family constitutes a complete solid-solution series, and is among the most frequent complex sulfides in Nature. This kind of structure can be generically expressed by the composition, Cu12Sb4S13. We have calculated the electronic band structure of Cu12Sb4S13 and Ag6Cu6Sb4S13 (with band gaps of 1.24 and 1.20 eV, respectively) to demonstrate that different elements occupying certain sites of the crystal structure will make a difference in what concerns the conduction process in Tetrahedrites. We will use this effect and ab initio calculations to show that the electronic properties of these compounds make them promising candidates as solar cells photovoltaic materials since not only they possess a direct band gap but their energy falls within the range of energies of photovoltaics. Moreover, we can optimize these properties by doping and substituting ions furthermore. Mechanical properties were also calculated for both compounds and will be compared.

Phase stability of ternary antifluorite type compounds in the quasi-binary systems Mg2X–Mg2Y (X, Y = Si, Ge, Sn) via ab-initio calculations

A first-principles study of the stability of ternary alloys based on the antifluorite structure with Mg2X chemical formula (X = Si, Ge and Sn) is reported in order to evaluate their potential for high temperature thermoelectric applications. For the end-members, we find that |EformMg2Si|<|EformMg2Sn|<|EformMg2Ge| in good agreement with the values in the literature. We find that only the Mg2Si–Mg2Ge alloys form complete series of solid solutions. This result agrees with published experimental results and CALPHAD assessments. We find that Mg2Si–Mg2Sn and Mg2Ge–Mg2Sn systems display a miscibility gap. Therefore, for the Mg2Si–Mg2Sn based alloys, our results qualitatively confirm a recent reassessment of this quasi-binary phase diagram done by Kozlov et al. (J. Alloy Compd509, 3326–3337 (2011)) and suggest that the same kind of quasi-binary phase diagram exists in the case of the Mg2Ge–Mg2Sn alloys with a lower critical demixing temperature. The currently best thermoelectric alloys Mg2Si1−xSnx are most likely a mixture of two-phases and therefore the stability of their thermoelectric properties for long time applications should be carefully studied.