Wide Range Of Solid Solutions Research Articles

MICROSTRUCTURE EVOLUTION AND DIELECTRIC PROPERTIES OF K3Li2Nb5O15 and BaTiO3 COMPOSITES

ABSTRACT Investigations of composite materials with two different crystal structured ferroelectric ceramics were carried out. In this study, phase development, sintering behavior and dielectric characteristics of the composites of tungsten bronze structured ferroelectric K3Li2Nb5O15 (KLN) and perovskite structured BaTiO3 (BT) were examined as a function of molar ratio x in (1−x) K3Li2Nb5O15−xBaTiO3. A wide range of solid solution of BT in KLN was observed and the lattice constants of KLN decreased with BT contents. However, the solubility of KLN in BT was very narrow. X-ray analysis revealed that both KLN and BT phases coexisted in the samples from x = 0.4 to x = 0.8. Therefore, two dielectric relaxation peaks were observed in the samples with x = 0.4 ∼0.8, each of which is originated from KLN and BT phase, respectively. The solid solution between KLN and BT decreased the TC of both KLN and BT to lower temperature.

Microstructure evolution and dielectric properties of K 3Li 2Nb 5O 15 and PbTiO 3 composites

Investigations of composite materials with two different crystal structured ferroelectric ceramics were carried out. In this study, phase development, sintering behavior and dielectric characteristics of the composites of tungsten bronze structured ferroelectric K 3Li 2Nb 5O 15 (KLN) and perovskite structured PbTiO 3 (PT) were examined as a function of molar ratio x in (1 − x) K 3Li 2Nb 5O 15– xPbTiO 3. A wide range of solid solution of PT in KLN was observed and the lattice constants of KLN decreased with PT contents. However, the solubility of KLN in PT was very narrow. X-ray analysis revealed that both KLN and PT phases coexisted in the samples from x = 0.4 to x = 0.9. Therefore, two dielectric relaxation peaks were observed in the samples with x = 0.4–0.8, each of which is originated from KLN and PT phase, respectively. The addition of PT to KLN increased the maximum dielectric constant at T C and shifted the T C to lower temperature. While T C of PT rich samples were not changed significantly with KLN.

Petrology of Mn carbonate–silicate rocks from the Gangpur Group, India

Metamorphosed Mn carbonate–silicate rocks with or without oxides (assemblage I) and Mn silicate–oxide rocks with minor Mn carbonate (assemblage II) occur as conformable lenses within metapelites and metacherts of the Precambrian Gangpur Group, India. The petrology of the carbonate minerals: rhodochrosite, kutnahorite, and calcite that occur in these two assemblages is reported. Early stabilisation of spessartine, aegirine, quartz, and carbonates (in a wide solid solution range) was followed by pyroxmangite, tephroite, rhodonite through decarbonation reactions. Subsequently, jacobsite, hematite, braunite, hollandite and hausmannite have formed by decarbonation–oxidation processes during prograde metamorphism. Textural characteristics and chemical composition of constituent phases suggest that the mineral assemblages reflect a complex relationship between protolithic composition, variation of X CO 2 (<0.2 to ∼0.3) and oxygen fugacity. A variation of X CO 2 and f O 2 would imply internal buffering of pore fluids through mineral reactions that produced diverse assemblages in the carbonate bearing manganiferous rocks. A minor change in temperature (from around 400 to 450 °C) does not appear to have had any major influence on the formation of different mineral associations.

A computational study of the effect of Li–K solid solutions on the structures and stabilities of layered silicate materials—an application of the use of Condor pools in molecular simulation

Computer modelling techniques were used to investigate the structures and stabilities of Li–K solid solutions of three different disilicate structures, employing a newly developed program based on symmetry arguments to identify identical configurations and hence eliminate unnecessary duplication of calculations. Even so, the large number of calculations needed to sample the complete set of configurations of a wide range of solid solutions necessitated the use of an extensive Condor pool of PC clusters, which afforded the necessary computing resources for this study. The results of our calculations show that in the wide range of Li–K solid solutions investigated, the mixed-cationic KLiSi2O5 material retains its original structure when the composition was varied, where six-membered rings of silica tetrahedra are linked to form continuous channels throughout the structure. The channel positions are found to be preferentially occupied by the potassium ions rather than by the smaller lithium ions. The original framework of the experimental K2Si2O5 structure, containing 14-membered rings of silica tetrahedra, similarly remains intact with the introduction of smaller lithium atoms into the bigger potassium lattice sites. However, the replacement of potassium ions for lithium ions in the Li2Si2O5 material causes significant distortions of the original structure, which loses its symmetry, although the ring structure remains.

Structural Studies on New Ternary Oxides Ba8Ta4Ti3O24 and Ba10Ta7.04Ti1.2O30

The ternary oxides Ba8Ta4Ti3O24 and Ba10Ta7.04Ti1.2O30 were synthesized and their crystal structures and defects were studied by means of X-ray powder diffraction, electron diffraction, and high resolution electron microscopy. The crystal structure of Ba8Ta4Ti3O24 is based on the 8H (cchc)2 close-packed stacking (a = 10.0314 Å, c = 18.869 Å, SG P63/mcm, Z = 3) and that of Ba10Ta7.04Ti1.2O30 and on the 10H (cchcc)2 close-packed stacking (a = 5.7981 Å, c = 23.755 Å, SG P63/mmc, Z = 1) of BaO3 layers. The structural refinements gave the following values for the R factors for Ba8Ta4Ti3O24 (Ba10Ta7.04Ti1.2O30) R1 = 0.041 (0.039), Rp = 0.108 (0.118), and RwP = 0.094 (0.099). The main feature of both structures is the presence of two types of face-sharing octahedra (FSO) with different occupancies by Ta atoms, Ti atoms, and vacancies, which results in the formation of a superstructure. It was shown that in the Ba8Ta4Ti3O24 structure these pairs of FSO occur in an ordered fashion and in the Ba10Ta7.04Ti1.2O30 structure in a disordered fashion. The existence of the wide range of solid solutions was shown to be also a consequence of the presence of one of the two types of face-sharing octahedra.

New Li+-ion conductors, Li4 – 2xTi1 –xSxO4, based on the Li4TiO4structure

In the system Li4TiO4–Li2SO4, a wide range of solid solutions, Li4 – 2xSxTi1 –xO4(0 < x < 0.2) with Li4TiO4 structure is formed. The ionic conductivity increases with x and exhibits a maximum (bulk) value of 8.30 × 10–6 S cm–1at 27 °C with an activation energy of 0.51 eV for x= 0.2. The enhancement in conductivity is associated with an increase in concentration of lithium-ion vacancies, created via the mechanism 2Li++ Ti4+⇌ S6+, but is attributable specifically to a decrease in activation energy for conduction. This is the first report of high Li+-ion conductivity in the Li4TiO4structural family.

New fast F − ionic conductors in the PbF 2-InF 3-ZrF 4 system

A wide range of solid solution with the fluorite-type structure is isolated within the PbF 2-InF 3-ZrF 4 system. It corresponds to the formulation: Pb 1− x In x(1− z) Zr xz F 2+ x(1+ z) (0⩽ z⩽ 1). The study of the electrical properties shows that the materials showing the best performance are characterized by the presence of column clusters of n = 2 dimension and by a value of the Zr/In ratio close to 1 2 . The results obtained are discussed on the basis of the clustering process model.

Search for superconductivity in analogues of La 2−xSr xCuO 4: Sr 2−xLn xVO 4 (Ln=La, Ce, Pr, Nd, Eu)

We report the preparation, unit cell parameters, and electrical conductivity of ceramic samples of Sr 2− x Ln x VO 4, in which there are formally (1+ x) d-electrons per transition metal, in analogy with the (1+ x) d-holes in the high temperature superconducting system La 2− x Sr x CuO 4. For Ln=La, Ce, Nd and Eu, we find a wide range of solid solution for 0.4≤ x≤1.. However, a complete solid solution for 0≤ x≤1 is found only in the case of Pr. All compounds are found to be semiconducting below room temperature, with no evidence of superconductivity.

Ag-clad Bi-Sr-Ca-Cu-O wires: II. Important factors in supersolidus phase studies

We studied the effect the quench rate has on the phase assemblage observed at room temperature in the Bi:Sr:Ca:Cu oxide system for Ag-clad 2:2:1:2 wire that had been quenced from above the solidus. Ag, which dissolved into the melt from the cladding, and “2201” precipitated out of the melt in samples quenched in liquid nitrogen or air due to the relatively slow quenching rate. In contrast, the quench rate in oil was rapid enough to prevent these phase from forming. In oil-quenched samples, “2201” was not observed indicating that “2201” is not a precursor phase to “2212”. These wire samples contained several minor phases that were difficult to identify in the multiphase X-ray diffraction patterns. We examined the X-ray diffraction pattern for (Sr 1− x Ca x )CuO 2 ( x=0.4), a phase found in the wire that has a wide range of solid solution and whose X-ray pattern is quite different than the end member SrCuO 2. Identifying and indexing the diffraction peaks due to this phase were aided by the quantitative chemical data we collected on each phase present in the wire.

Influence of Zro2 on the microstructure of BaTiO3

Ceramic capacitor materials are typically based on ferroelectric perovskite structures such as BaTiO3. The desirable electrical properties can be improved by isovalent additions of cations such as Ca2+ for Ba2+ and Zr4+ for Ti4+ These additions are aliostructural with the BaTiOg perovskite lattice and create a wide range of solid solutions and property modifications. Additions of ZrO2 both decrease and broaden the dielectric constant peak at the Curie temperature and have been shown to increase the lattice parameter of BaTiO3 resulting in a decrease in the c/a ratio. ZrO2 is believed to affect the dielectric properties by residing at the grain boundaries and suppressing grain growth. The induced strain, resulting from suppressed grain growth, stabilizes the dielectric constant by suppressing the displacive phase transformations and results in a pseudo-cubic structure. The objective of this investigation was to determine the effects of added ZrO2 on the microstructure and grain boundary of BaTiO3.

Alpine metamorphic evolution of Ligurian Alps (North-West Italy): chemography and petrological constraints inferred from metamorphic climax assemblages

The up-to-date petrological and microtextural information on the Ligurian Alps indicates that the metamorphic rocks from the oceanic lithosphere and the paleo-European continental margin underwent an alpine-type metamorphic evolution characterized by low dT/dP gradients. In particular, rocks from the Ligurian-Piedmontese oceanic lithosphere underwent an alpine metamorphism typical of alpine-type blueschist rocks. The distribution of the alpine metamorphic facies in paleo-European continental margin is closely related to the structural position of the different tectonic units. The prograde evolution frequently preserves paragenetic and textural relics of the earlier parageneses. If relics of the earlier parageneses are preserved, the rock exhibits continuous prograde reactions confirmed by strong compositional zoning of the metamorphic minerals. Therefore, these reactions lead to chemical and microtextural equilibrium relations, between the minerals, in limited domains of the rocks (microtextural sites). The main compositional aspect of coronitic textures is the mineral zoning, particularly when the minerals of the coronas are the consequence of a wide range of solid solutions. In such cases, the reacting minerals are armored and the kinetics are lowered. The prograde metamorphic evolution, which involved the rocks from the oceanic lithosphere and the paleo-European continental margin, is quite consistent with a subduction-type geodynamic process in different ages during alpine times.

Jadeite-kosmochlor solid solution and chromian sodic amphiboles in jadeitites and associated rocks from Tawmaw (Burma)

Jadeitites from Tawmaw (Burma) and associated amphibolites display chromian pyroxene — and amphibole-bearing parageneses, formed during a high pressure — low temperature metamorphic event. Sodic pyroxene compositions confirm the occurrence of kosmochlor in terrestrial rocks ; they show a wide range of solid solution between pure jadeite and kosmochlor 85, but suggest the existence of a miscibility gap between Ko25 and Ko50 under these metamorphic conditions. The sodic amphiboles, katophorite, glaucophane and eckermannite, contain up to 10 % Cr2O3. These exceptional compositions were formed in a particular chemical environment resulting from metasomatic reaction between an albitite dyke containing chromite xenocrysts and the enclosing serpentinites during metamorphism.

The hydrides of TmCo 3

Abstract Hydrogen desorption isotherms were measured in the system DyCo 3 H x for 0⩽ x ⩽ 4.25 at temperatures of 0, 20, 40, 60 and 80 °C. Pressure plateaus on the isotherms indicate the existence of two hydride phases in addition to the terminal hydrogen-saturated metal α phase. Both hydrides exhibit a wide range of solid solution. The β phase runs from x = 1 to x = 1.83, whilst the γ phase runs from x = 3.1 to at least x = 4.25. The α phase is very narrow. At 20 °C the plateau pressures are 3 and 54 Torr and the heats of absorption are −11.43 and −9.75 kcal (mol H 2 ) −1 respectively. From the temperature dependence of the isotherms, the partial molar heats and entropies of absorption and the heats and entropies of formation were calculated as functions of x .

Thermodynamic properties of HoCo 3 hydrides

Hydrogen desorption isotherms were measured in the system HoCo xH x. for 0 ⩽ x ⩽ 4.1 at temperatures of 0, 20, 40, 60 and 80°C. Pressure plateaus on the isotherms indicate the existence of two hydride phases in addition to the terminal hydrogen-saturated metal α phase. Both hydrides exhibit a wide range of solid solution. The β phase extends from x = 0.95 to x = 1.72, while the 7 phase extends from x = 3.15 to at least x = 4.10. The α phase is very narrow. At 20°C the plateau pressures are 6.49 and 121 Torr, and the heats of absorption are −11.28 and −9.26 kcal (mol H 2) −1. From the temperature dependences of the isotherms, the partial molar heats and entropies of absorption and the heats and entropies of formation were calculated as functions of x.

Thermodynamic properties of ErCo 3 hydrides

Hydrogen desorption isotherms were measured in the system ErCo 3H x for 0 ⩽ x ⩽ 4.15 at temperatures of 0, 20, 40, 60 and 80 °C. Pressure plateaus on the isotherms indicate the existence of two hydride phases in addition to the terminal hydrogen-saturated metal α phase. Both hydrides exhibit a wide range of solid solution. The β phase runs from x = 1.15 to x = 1.65, whilst the γ phase runs from x = 3.55 to at least x = 4.15. The α phase is very narrow. At 20 °C the plateau pressures are 18.8 and 265 Torr, and the heats of absorption are −10.55 and −8.76 kcal (mol H 2) −1 respectively. From the temperature dependence of the isotherms, the partial molar heats and entropies of absorption and the heats and entropies of formation were calculated as functions of x.

The hydrides of DyCo 3

Hydrogen desorption isotherms were measured in the system DyCo 3H x for 0⩽ x ⩽ 4.25 at temperatures of 0, 20, 40, 60 and 80 °C. Pressure plateaus on the isotherms indicate the existence of two hydride phases in addition to the terminal hydrogen-saturated metal α phase. Both hydrides exhibit a wide range of solid solution. The β phase runs from x = 1 to x = 1.83, whilst the γ phase runs from x = 3.1 to at least x = 4.25. The α phase is very narrow. At 20 °C the plateau pressures are 3 and 54 Torr and the heats of absorption are −11.43 and −9.75 kcal (mol H 2) −1 respectively. From the temperature dependence of the isotherms, the partial molar heats and entropies of absorption and the heats and entropies of formation were calculated as functions of x.

Phase diagram of the LISICON, solid electrolyte system, Li4GeO4-Zn2GeO4

The phase diagram of the system Li4GeO4-Zn2GeO4 is fairly similar to the corresponding silicate system and contains a wide range of solid solutions that extend to either side of the composition Li2ZnGeO4. These solid solutions are polymorphic. The high temperature γII solid solutions have a crystal structure derived from that of γII Li3PO4 and a formula, Li2 + 2xZn1−xGeO4 : −0.36 <x < +0.87. LISICON, x = 0.75, is one member of the γII solid solution series. The compositional extent of the γII solid solutions is temperature dependent and eg. the LISICON composition is stable as a single phase γII structure only ≳ 630°C. On annealing LISICON and other lithiumrich, γII solid solutions in the range ∼100 to 600°C, various reactions occur, including 1) precipitation of Li4GeO4, 2) phase transition(s) to metastable low temperature, γ-derivative structure(s) and 3) atmospheric attack to give Li2GeO3, Li2CO3 and other phases. The low temperature βII, βII′ solid solutions occur over a much smaller range of compositions to either side of Li2ZnGeO4 and have a crystal structure derived from that of βII Li3PO4. Li4GeO4 forms a short range of solid solutions.

Solid-Solution Oxides for Storage-Battery Electrodes

Insertion compounds contain a mobile cation of variable concentration over a wide range of solid solution. Charge compensation is achieved by a variation of mobile-electron concentration in the host matrix. Such mixed ionic/electronic conductors are of practical interest as electrodes in secondary batteries and electrochromic displays. Oxides containing transition-metal ions in unusually high valence states can be prepared by room-temperature extraction of mobile cations from such structures. Some properties of the systems Li1-yCoO2 and Na1-yCoO2 are presented.

The optical properties of Sb2Se3Sb2Te3

AbstractThe optical properties of single crystal specimens of Sb2Te3Sb2Se3 solid solutions have been investigated in the photon energy range 0.04 eV to 6.5 eV. A wide range of solid solutions having hexagonal structure were found to exhibit properties closely corresponding to the isostructural compounds Bi2Te3 and Bi2Se3. Small indirect band gaps approaching semimetallic values were obtained. The high free‐carrier concentrations gave rise to plasma effects in the near infra‐red. In contrast Sb2Se3 is orthorhombic with a direct band gap near 1 eV. The chemical bonding concepts applied to similar systems seem applicable with only slight modification.

X-ray study of the effect of palladium on stacking fault densities of Ag-base alloys

Stacking fault densities α and β of the Ag–Pd alloy system were determined from peak shift and peak asymmetry measurements of the X-ray diffraction line profiles recorded by a Geiger counter X-ray diffractometer. The concentration of the fault probabilities was found to be small. From Fourier analysis of line shapes the anisotropic values of the effective particle sizes, [De]hkl and root mean square strains, [〈∊L2〉]hkl1/2, were obtained in all cases. No appreciable change in [De]hkl and [〈∊L2〉]hkl1/2 was observed for a wide solid-solution range. The observed particle-size broadening is primarily a consequence of deformation and twin faults and a fair agreement has been observed for the compound fault probability (1.5α + β) obtained from the two different methods.