Continuous Series Of Solid Solutions Research Articles

Interaction between lead bromide and barium bromide

The phase diagram of the PbBr2-BaBr2 system over the entire concentration range is studied for the first time by differential thermal analysis and X-ray powder diffraction analysis. No new compounds are formed in the system. The phase diagram is represented by a continuous series of solid solutions (type I by Rooseboom’s classification). The unit cell parameters change as a linear function of composition.

Isothermal section of Gd-Sm-Co ternary system at 773 K

The isothermal section of the phase diagram of the Gd-Sm-Co ternary system at 773 K was investigated by X-ray powder diffraction (XRD), differential thermal analysis (DTA)optical microscopy and scanning electron microscopy (SEM) techniques. The result shows that the isothermal section consists of 12 single-phase regions, 16 two-phase regions and 5 three-phase regions. Five pairs of corresponding compounds of Gd-Co and Sm-Co systems, i.e., Gd2Co17 and Sm2Co17, Gd2Co7 and Sm2Co7, GdCo3 and SmCo3, GdCo2 and SmCo2, Gd3Co and Sm3Co form continuous series of solid solutions. The maximum solid solubility of Sm in Gd4Co3 and Gd12Co7 were about 7.2 at.% and 47.8 at.% Sm, respectively. The maximum solid solubility of Gd in Sm5Co19 and Sm5Co2 were about 4.7 at.% and 7.6 at.% Gd, respectively. The binary compounds Sm9Co4, GdCo5 and SmCo5 were not observed at 773 K. No ternary compound was found.

Synthesis, characterization and stability properties of Cl-bearing hydrotalcite-pyroaurite solids

Abstract A layered double hydroxides (LDH) hydrotalcite-pyroaurite solid solution series (Mg1−x Fe(II) x )3Al1Cl1·nH2O with variable xFesolid = Fe2+/(Fe2++Mg2+) iron mole fractions were studied in co-precipitation experiments at T = 25, 40, 45, 50, 55 and 60 ºC and pH = 10.00 ± 0.05. The compositions of the solids and reaction solutions were determined using ICP-OES, EDX (Mg, Al, Fe) and TGA techniques (Cl−, OH−, H2O). Powder X-ray diffraction was applied for phase identification and determination of unit-cell parameters a o = b o and c o from Bragg evaluation. Syntheses products containing xFesolid > 0.13 display additional X-ray patterns attributed to the mixture of iron oxides and hydroxides. On the other side, precipitates with 0 ≤ xFesolid ≤ 0.13 show only X-ray reflexes typical for pure LDH compositions. Moreover, in this case unit-cell parameters a o = b o as a function of xFesolid follow Vegard's law corroborating the existence of a continuous solid solution series. TGA data demonstrated the temperatures at which interlayer H2O molecules and Cl−-anions are lost, and at which temperatures dehydroxylation of brucite-like layer occurs. Based on detailed analyses of TGA curves it was established that the increase of xFesolid does not result in a visible change of the thermal stability of hydrotalcite-pyroaurite solids. From the chemical analyses of both the solids and the reaction solutions after syntheses, preliminary Gibbs free energies of formation were estimated by using GEMS-PSI code package. Values of Gºf (Hydrotalcite) = −3619.04 ± 15.27 kJ/mol and Gºf(Pyroaurite) = −2703.61 ± 191.93 kJ/mol were found at 298.15 K. A comparison of our estimate with Gºf value −3746.90 ± 11.00 kJ/mol for CO3 2−-bearing hydrotalcite presented in our previous studies, denotes the effect of intercalated anion on the aqueous solubilities of LDH when Cl-containing solids have to be more soluble than CO3 2−-bearing substances. Estimation of the standard molar entropy of the hydrotalcite end-member by applying Helgeson's methods and using results of co-precipitation experiments at variable temperatures let us to conclude that derivation of more precise Sºf values would require calorimetric measurements.

Phase diagrams of the SrEr2S4-SrLn2S4 (Ln = Nd, Dy, Yb) systems

The phase diagrams of the SrEr2S4-SrLn2S4 (Ln = Nd, Dy, Yb) systems were constructed, and the diagrams of the SrLn′2S4-SrLn″2S4 (Ln′, Ln″ = La-Lu) systems were predicted. The diagram of the SrEr2S4-SrNd2S4 system is of the eutectic type. The diagrams of the SrEr2S4-SrDy2S4 and SrEr2S4-SrYb2S4 systems involve the formation of a continuous series of solid solutions with the rhombic structure of the CaFe2O4.

Synthesis and crystal structures of new oxyapatites BiCa4−xLax(VO4)3−x(GeO4)xO, x=1–3

New germanate–vanadates with the general formula BiCa4−xLax(VO4)3−x(GeO4)xO, x=1−3, have been synthesized by the nitrate–citrate method and characterized. Structural refinement based on X-ray powder diffraction data showed that these compounds are isostructural with BiCa4(VO4)3O (space group P63/m (N 176), Z=2, а=9.8327–9.8755(3), and с=7.1203–7.2133(2)). They may be viewed as continuous series of solid solutions where Ca2+ and V5+ cations in the crystal lattice of vanadate BiCa4(VO4)3O are replaced by La3+ and Ge4+ cations. In the process of substitution, the La3+ cations occupy mainly the 4f lattice sites of the germanate–vanadate oxyapatites, but the filling of the 4f and 6h lattice sites in the germanate BiCaLa3(GeO4)3 is equivalent. IR and Raman spectra were studied. The Raman spectra clearly show a two-mode behavior: the lines of GeO4 and VO4 are separated from each other, and the (V/Ge)O4 tetrahedra exhibit a quasi-independent behavior.

Synthesis of substitutional solid solutions in Na2O-P2O5-In2O3-M 2 III O3 (MIII = Cr, Fe, and Mn) systems

Solid solutions based on Na7(InP2O7)4PO4 and Na3In2(PO4)3, where chromium, iron, and manganese substitute for indium, have been prepared. When chromium and iron substitute for indium in Na7(InP2O7)4PO4, a continuous solid solution series exists. When manganese substitutes for indium, it enters the compound in the oxidation state +3. The substitution of chromium for indium in Na3In2(PO4)3 occurs within the range from 0.11 to 0.74 (mol/mol), and that of iron for indium, from 0.09 to 0.62 (mol/mol). When manganese substitutes for indium, it enters the structure of the crystalline phase in insignificant amounts as a two-charged cation.

Scandium as an Element Intermediate between Rare Earth and Transition Metals in Intermetallics: Crystal Structures of Sc2Fe12P7, Sc3.6Fe10.4P7, and Sc2Co4P3. Other New Compounds with Zr2Fe12P7, Hf2Co4P3, Sc5Co19P12, and Yb6Co30P19 Type Structures

AbstractAbstract. Twenty five ternary phosphides crystallizing with four different but closely related structure types were prepared using elemental tin as a flux. Their lattice constants are reported. New compounds include Sc2Fe12P7, Sc3.6Fe10.4P7, Y2Co12P7, and Hf2T12P7 with T = Fe, Co, Ni. They crystallize with the hexagonal Zr2Fe12P7 type structure, which was refined from single‐crystal X‐ray data of Sc3.6Fe10.4P7: a = 944.1(1) pm, c = 363.4(1) pm, R = 0.041 for 719 unique structure factors and 23 variable parameters. The excess scandium atoms occupy one of the four iron sites of the Zr2Fe12P7 type structure which has a higher coordination number than the other three iron sites. The two isotypic phosphides Sc2Fe12P7 and Sc3.6Fe10.4P7 do not form a continuous series of solid solutions. The new compounds Sc2Co4P3 and Sc2Ni4P3 are isotypic with Hf2Co4P3. This hexagonal structure was refined for Sc2Co4P3 from single crystal data: a = 1211.5(2) pm, c = 363.7(1) pm, R = 0.025 for 500 Fo and 38 variables. Other new compounds reported are Sc5Ni19P12, Zr5Fe19P12, Hf5Fe19P12, and Hf5Co19P12 which crystallize with Sc5Co19P12 type structure, and the Yb6Co30P19 type phosphides Sc6Co30P19, Zr6Co30P19, and Hf6Co30P19. The structural relationships of these ternary phosphides are discussed with special attention to the environments of the transition metal atoms.

Raman spectroscopic study of the mineral arsenogorceixite BaAl3AsO3(OH)(AsO4,PO4)(OH,F)6

Arsenogorceixite BaAl3AsO3(OH)(AsO4,PO4)(OH,F)6 belongs to the crandallite mineral subgroup of the alunite supergroup. Arsenogorceixite forms a continuous series of solid solutions with related minerals including gorceixite, goyazite, arsenogoyazite, plumbogummite and philipsbornite. Two minerals from (a) Germany and (b) from Ashburton Downs, Australia were analysed by Raman spectroscopy. The spectra show some commonality but the intensities of the peaks vary.Sharp intense Raman bands for the German sample, are observed at 972 and 814cm−1 attributed to the ν1 PO43− and AsO43− symmetric stretching modes. Raman bands at 1014, 1057, 1148 and 1160cm−1 are attributed to the ν1 PO2 symmetric stretching mode and ν3 PO43− antisymmetric stretching vibrations. Raman bands at 764 and 776cm−1 and 758 and 756cm−1 are assigned to the ν3 AsO43− antisymmetric stretching vibrations. For the Australian mineral, the ν1 PO43− band is found at 973cm−1. The intensity of the arsenate bands observed at 814, 838 and 870cm−1 is greatly enhanced.Two low intensity Raman bands at 1307 and 1332cm−1 are assigned to hydroxyl deformation modes. The intense Raman band at 441cm−1 with a shoulder at 462cm−1 is assigned to the ν2 PO43− bending mode. Raman bands at 318 and 340cm−1 are attributed to the (AsO4)3−ν2 bending. The broad band centred at 3301cm−1 is assigned to water stretching vibrations and the sharper peak at 3473cm−1 is assigned to the OH stretching vibrations. The observation of strong water stretching vibrations brings into question the actual formula of arsenogorceixite. It is proposed the formula is better written as BaAl3AsO3(OH)(AsO4,PO4)(OH,F)6·xH2O. The observation of both phosphate and arsenate bands provides a clear example of solid solution formation.

Crystal structure and magnetic properties of DyCuxGa2−x (x = 0–2.0) antiferromagnetic compounds

DyCuxGa2−x (x=0–2.0) compounds have been synthesized; meanwhile, their crystal structure and magnetic properties have been investigated by X-ray diffraction and magnetic measurements. The result shows that the continuous solid-solution series crystallize in three phases, with the structure types of AlB2 (x=0–0.2), DyCuGe (x=0.3–0.6) and CeCu2 (x=0.7–2.0), respectively. The main reason to form the three structure types is considered to be the average atomic radius ratio of R to Cu/Ga. Magnetic-ordering transition of the compounds with x=0.2–0.6 takes place at about 20K and 113K, while those of other compounds only takes place at about 20K, which is attributed to the change of the near Dy–Dy distances and the ordered substitution of Ga by Cu.

Analysis of solid solutions stability in scheelite-type molybdates and tungstates

Mutual solubility of bivalent metal molybdates and tungstates with scheelite structure was theoretically estimated by calculating formation enthalpies and the maximal decomposition temperatures of solid solutions at different temperatures. The theoretical stability of continuous solid solutions in binary systems of bivalent metal molybdates and tungstates was found to be higher than reported literature data. After cooling down continuous substitution solid solution should remain in following systems: CaMoО 4–CdMoО 4, SrMoО 4– MMoО 4 ( M=Ba, Pb), BaMoО 4–PbMoО 4, SrWO 4– MWO 4 ( M=Ca, Pb), and BaWO 4–PbWO 4. There is a probability that at room temperature in systems CaMoО 4–SrMoО 4, CaWO 4–PbWO 4, and BaWO 4–SrWO 4 the single homogeneity region may decompose to limited solid solutions. It was shown experimentally that a continuous series of scheelite-structure solid solutions M 1− x M I x ТO 4 can be formed via citrate synthesis at temperatures below 500°С.

Phase equilibria in the Tl2Se-PbSe system and growth and properties of Tl4PbSe3 single crystals

The T-x phase diagram of the Tl2Se-PbSe system has been mapped out. The system contains a congruently melting compound (803 K) of composition Tl4PbSe3, which forms a continuous series of solid solutions with Tl2Se. Tl4PbSe3 single crystals have been grown by directional solidification, and their physicochemical and thermoelectric properties have been studied. Tl4PbSe3 crystals have high thermopower (α T ) and thermoelectric figure of merit (Z T ).

Structure and dielectric properties of (1 − x)BiFeO3 · x(KBi)1/2TiO3 perovskite solid solutions

(1 − x)BiFeO3 · x(KBi)1/2TiO3 ceramics have been prepared by solid-state reactions. The system has been shown to contain a continuous series of perovskite solid solutions. In the composition ranges x 0.9, the solid solutions have rhombohedral, orthorhombic, and tetragonal structures, respectively. The observed compositional phase transitions are accompanied by sharp changes in unit-cell volume. We describe the dielectric properties of the orthorhombic solid solutions, which demonstrate that these materials exhibit relaxor behavior.

Investigation on the isothermal section of the Gd–Ni–Y ternary system at 773 K

The isothermal section of the phase diagram of the Gd–Ni–Y ternary system at 773 K was investigated by means of X-ray powder diffraction, metallographic analysis and scanning electron microscopy with energy dispersive analysis. The isothermal section consists of 12 single-phase regions, 15 two-phase regions and 4 three-phase regions. Six pairs of corresponding compounds in the Gd–Ni and Y–Ni systems, i.e., Gd 2Ni 17 and Y 2Ni 17, GdNi 5 and YNi 5, Gd 2Ni 7 and Y 2Ni 7, GdNi 3 and YNi 3, GdNi 2 and YNi 2, Gd 3Ni and Y 3Ni and metals Gd and Y form a continuous series of solid solutions, respectively. At 773 K, the maximum solubilities of Gd in YNi and Y in GdNi were about 20 at.% Gd and 8 at.% Y, respectively. No solubility of Gd in YNi 4 and Y in GdNi 4 was observed.

Constitution of ZrCo–ZrIr alloys

A physicochemical analysis is used to examine the constitution of ZrCo–ZrNi alloys for the first time. The equiatomic ZrCo and ZrIr phases are found to form a continuous series of solid solutions over a range from the subsolidus temperature to the starting temperature of martensite transformation in ZrIr. The substitution of Co for Ir stabilizes the high-temperature ZrIr phase with a CsCl type structure. The extrapolation of linear temperature dependence of cobalt content shows that the hightemperature phase is stable at room temperature in the alloy containing about 15 at.% Co.

Analysis of the change in the Gibbs energy during the formation of a continuous series of substitutional solid solutions from liquid solutions

Geometrical thermodynamics is used to analyze the variation of the Gibbs energy with the temperature and concentration of metallic alloy components with unlimited solubility for liquid, liquid-solid, and solid states.

Solubility of pyromorphite Pb 5(PO 4) 3Cl–mimetite Pb 5(AsO 4) 3Cl solid solution series

Pyromorphite Pb 5(PO 4) 3Cl and mimetite Pb 5(AsO 4) 3Cl are isostructural minerals with apatite. Due to their high environmental stability, they have gained considerable attention as metals sequestration agents in water treatment and contaminated soil remediation. Pyromorphite and mimetite can form a continuous solid solution series in near-Earth surface environments. Precipitation of the end members and intermediate members of the series is likely to occur in the areas where the cost-effective in situ immobilization reclamation method, based on phosphate amendments, is applied. In contrast to the widely studied thermodynamic parameters of pyromorphite and mimetite, knowledge of the thermodynamics of their solid solutions is sparse. To supplement the data, a number of compounds from the pyromorphite–mimetite series were synthesized at room temperature using a method to simulate the conditions in the near-Earth surface environments. Afterwards, batch dissolution and dissolution–recrystallization experiments of seven synthesized precipitates were conducted at 25 °C, pH = 2 and in a 0.05 M KNO 3 background electrolyte. The experiments were carried out for a period of 6 (dissolution) and 14 (dissolution–recrystallization) months. A plateau in the [Pb] evolution patterns was used to determine equilibrium. All seven dissolutions were congruent, and the ionic activity products (IAP) of the minerals from the pyromorphite–mimetite solid solution series were calculated based on the dissolution reaction: Pb 5 ( PO 4 ) n ( AsO 4 ) 3 - n Cl ↔ 5 Pb 2 + + n PO 4 3 - + ( 3 - n ) AsO 4 3 - + Cl - . The IAPs for pyromorphite and mimetite exhibit a significant difference in values over three orders of magnitude between approximately 10 −79 for pyromorphite and approximately 10 −76 for mimetite. The series appeared to be ideal, and Lippmann and Roozboom diagrams were used for better understanding of its thermodynamics. The results indicated a strong tendency of pyromorphite to partition into the solid phase in the series, which explains some of the naturally observed phenomena. The improvement of the lattice stability of the mimetite due to isostructural phosphate substitutions in anionic sites was observed. The thermodynamic data reported in this study supplement existing databases used in geochemical modeling.

Synthesis and study of yttrium aluminum garnets doped with neodymium and ytterbium

Ytterbium- and neodymium-substituted yttrium aluminum garnets were obtained by hydroxide coprecipitation and by the cryochemical method. A continuous series of solid solutions in the Y3Al5O12 — Yb3Al5O12 system and limited solid solutions (NdxY1 − x)3Al5O12 (0 ≤ x ≤ 0.19) were obtained. The synthetic methods used made it possible to reduce the synthesis temperature from 1800 to 950°C and to obtain more homogeneous and nanosized material.

Isothermal section of the Co–Er–Y ternary system at 500 °C

The isothermal section of the phase diagram of the Co–Er–Y ternary system at 500 °C was investigated by X-ray powder diffraction technique, differential thermal analysis, scanning electron microscopy with energy dispersive analysis and optical microscopy. The 500 °C isothermal section consists of 14 single-phase regions, 19 two-phase regions, and 6 three-phase regions. Six pairs of corresponding compounds Er 2Co 17 and Y 2Co 17, Er 2Co 7 and Y 2Co 7, ErCo 3 and YCo 3, ErCo 2 and YCo 2, Er 4Co 3 and Y 4Co 3, Er 3Co and Y 3Co and metals Y and Er form a continuous series of solid solutions. The maximum solid solubility of Y in the compounds Er 12Co 7 is about 19 at.% Y.

Formation of a continuous series of Ti–Cr–Fe bcc solid solutions in a powder mixture ground in a planetary-ball mill

The paper examines the formation of a continuous series of titanium and chromium solid solutions with iron admixtures ground in an AIR-015M planetary-ball mill. A non-equilibrium cubic β-titanium phase forms under intensive milling of titanium and chromium powders due to decrease in the grain size to the nanoscale at relatively low temperatures (T < 0.3T m ). A continuous series of titanium-chromium bcc solid solutions is obtained owing to intensive milling in an AIR-015M planetary-ball mill and favorable conditions for the formation of a non-equilibrium structure of titanium.

Single crystal preparation and properties of the AgGaGeS4–AgGaGe3Se8 solid solution

Phase equilibria in the AgGaGeS4–AgGaGe3Se8 system were investigated using differential-thermal analysis and phase X-ray diffraction. A continuous solid solution series was discovered in the system, and the mechanism of the formation of these solid solutions was determined. Single crystals of the solid solutions were grown by the Bridgman–Stockbarger method. The crystals are of n- or p-type conductivity and their bandgap energy varies from 2.25 to 2.80eV.