Phase Composition and Compatibilities in the Bi-Sr-Ca-Cu Quaternary Oxide System at 800°C in Air

Subsolidus phase relations in the system (Bi-Sr-Ca-Cu)-O at 800°C were investigated via powder X-ray diffraction and electron probe microanalysis of solid-state reaction products. Two recently reported (Bi-Sr-Ca)-O phases were detected in quaternary assemlages and had the approximate cation stoichiometries of 9 11 5 and 825. The only truly quaternary compound detected is the superconducting phase with the cation stoichiometry 2212. Tie lines, tie triangles, and compatibility tetrahedra involving this phase and the 2201 superconducting phase were determined. Both superconducting compounds exhibit small but detectable Sr-to-Ca solubility and are Sr-deficient with respect to the "ideal" formulas.     

Phase Composition and Compatibilities at 930° to 950°C in the System Europium(III) Oxide-Barium Oxide-Copper(II) Oxide in Air

Phase composition and compatibilites at 930° to 950°C were determined for the system Eu₂O₃–BaO–CuO in air. The binary compound Eu₂CuO₄ dissolves Ba to the extent 0 x 0.02 in Eu_2-xBa_xCuO₄, whereas the other binary compounds, Eu₂BaO₄ and BaCuO₂, do not exhibit solid solubility. Three ternary compounds were obtained, Eu₂BaCuO₅ and two solid solution phases. The first contains the 90 K '123' superconductor and has solubility limits represented by Eu_1+xBa_2-xCu₃O_7±y, where 0 x 0.5. The second has a solubility limit represented as Eu_1+xBa_8-xCu₄O_y, where 0 x 0.44. The limited solid solution range of this phase provides insight concerning the probable solid solution range of the analogous phase in the Y₂O₃-BaO-CuO system.     

New Phases in the CaO–M2O3–CuO (M = Nd, Gd, Y) Systems at 1000°C

New layered cuprates with the general stoichiometry Ca_{2+ x} M_{2− x} Cu₅O₁₀ have been characterized for M = Nd, Gd, and Y. These insulating phases have structures closely related to that of NaCuO₂ and contain one-dimensional chains constructed from edge-sharing [CuO₄] square planes. The X-ray patterns of these ternary cuprate phases are complicated by strong reflections from both incommensurate and commensurate supercells which result from the ordering of the Ca²⁺ and M³⁺ ions in the structure. The stoichiometry range, and resultant Cu valences in these cuprates depend upon the nature of the trivalent ion. Ca-rich and trivalentrich compositions can be prepared for M = Nd and Gd, but only Ca-rich compositions were formed in the Y system. No other ternary phases are observed under the conditions of this study, 1000°C in air, and the solid-state equilibria are dominated by the single ternary phase identified above.     

Phase Relations and Thermal Expansion Studies in the Ceria–Yttria System

The synthesis, characterization, and bulk and lattice thermal expansions of a series of compounds with general composition Ce_{1– x} Y _x O_{2– x /2} (0.0 ≤ x ≤ 1.0) are reported. The XRD pattern of each product was refined to learn the solid solubility limit and the homogeneity range. The solid solubility limit of YO_1.5 in CeO₂ lattice, under the conditions of slow cooling from 1400°C, is represented as Ce_0.55Y_0.45O_1.775 (i.e., 45 mol% of YO_1.5). The subsequent compositions were biphase. There was no solubility of CeO₂ into the lattice of YO_1.5. The bulk thermal expansion measurements from ambient to 1123 K, as investigated using a dilatometer, revealed that the α_l (293–1123 K) values, within the homogeneity range, decreased on increased Y³⁺ content. A similar trend was observed for average lattice thermal expansion coefficient, α_a (293–1473 K), as investigated using high-temperature XRD. No ordered phases were obtained in this system under the used conditions. These studies on Ce_{1– x} Y _x O_{2– x /2} (0.0 ≤ x ≤ 1.0) system can be used to simulate the phase relation and thermal expansion behavior of Pu_{1– x} Y _x O_{2– x /2} (0.0 ≤ x ≤ 1.0), because CeO₂ is widely used as a surrogate material for PuO₂.     

Pyroxene-Type (K,Na,Li)VO3 Solid Solutions

Phase relations in the system were studied between 600° and 350°C. All three end members have the pyroxene-type structure. Both LiVO₃ and NaVO₃ are monoclinic, whereas KVO₃ takes the orthorhombic symmetry. At 360°C, the join LiVO₃–NaVO₃ is characterized by two series of pyroxene-type solid solutions: NaVO₃–(Na_0.44Li_0.56)VO₃ and LiVO₃-(Na_0.16Li_0.84)-VO₃. (K_0.5Na_0.5)VO₃ and (K_0.5Li_0.5)VO₃ are two other stable phases at 360°C. The pyroxene-type (K_0.5Na_0.5)VO₃ has a range of solid solution from (K_0.6Na_0.4)VO₃ to (K_0.4Na_0.6)VO₃ along the join and extends into the ternary field with a maximum of 13 mol% LiVO₃. (K_0.5Li_0.5)VO₃ has no detectable range of solid solution, and its X-ray powder diffraction data cannot be indexed based upon either the monoclinic or the orthorhombic unit cell.     

Experimental Determination and Thermodynamic Calculation of the Zirconia–Calcia–Magnesia System at 1600°, 1700°, and 1750°C

Phase relations in the ternary system ZrO₂–CaO–MgO were experimentally established at 1600°, 1700°, and 1750°C. The investigation was based on powder X-ray diffractometry, scanning electron microscopy–energy dispersive spectroscopy, and electron probe microanalysis, on 24 ternary compositions. The compositions were prepared using attrition milling of respective oxides and carbonates as raw materials. The results obtained allowed construction of the corresponding isothermal sections, which verified the existence of the cubic-ZrO₂–CaZrO₃ phase compatibility field at the three temperatures. Finally, experimental results also were compared with the thermodynamic assessment previously reported of the system ZrO₂–CaO–MgO.     

2223 Phase Formation in Bi(Pb)─Sr─Ca─Cu─O: I, The Role of Chemical Composition

The formation of superconducting phases in the Bi(Pb)─Sr─Ca─Cu─O system has been systematically investigated using DTA/TG, XRD, SEM/EDAX, TEM, EPMA, ICP-AES, fourprobe dc resistance, and ac susceptibility. Starting compositions, firing temperature, and the duration of heat treatment, together with the atmosphere, were found to be critical in determining the preferred formation of the 2223 phase. This paper reports the effect of the initial chemical composition, emphasizing the importance of compositional control in the synthesis of the single 2223 phase. It has been shown that, with a correct starting composition and predetermined synthesis conditions, single 2223 phase can be obtained without intergrowth by the 2212 and other impurity crystalline phases. The optimum starting composition for the preferred growth of the 2223 phase was identified as being Bi_1.7Pb_{0.3+ y} Sr₂Ca₂Cu₃O _x ( y = 0.1), with excess Pb added in order to compensate for its loss at high temperatures. The effect of Pb doping and excess Cu on the phase formation in the Bi oxide based superconducting system is discussed.     

Phase Relations in the System Iron Oxide–NiO–SiO2 under Strongly Reducing Conditions

Liquidus and solidus phase relations have been determined for the system iron oxide–NiO–SiO₂ under strongly reducing conditions obtained by using CO₂–CO gas mixtures in controlled proportions. The phase relations were determined with the well-known quenching method: oxide mixtures were equilibrated in vertical tube resistance furnaces, followed by quenching to room temperature and identification of phases with transmitted- and reflected-light microscopy and X-ray diffraction. Three crystalline phases are present on the liquidus surface: olivine (Fe₂SiO₄–Ni₂SiO₄ solid solutions), oxide ("FeO"–NiO solid solutions), and silica (tridymite or cristobalite, depending on temperature). The "ternary peritectic" point where these three phases coexist with liquid is at 1571°C, with a liquid composition of approximately 19 wt%"FeO", 47 wt% NiO, 34 wt% SiO₂.     

Phase Relationships in the Ternary System CaO─P2O5─H2O at 25°C

The portion of the stable phase diagram for the ternary system CaO-P₂O₅-H₂O involving calcium phosphate phases more basic than Ca(H₂PO₄)₂ has been constructed. Construction involves plotting concentrations as their fifth roots to allow phases having very different solubilities to be represented on a single diagram. Hydroxyapatite is shown to be congruently soluble. The stability region for hydroxyapatite includes compositions having Ca/P ratios extending between 1.5 and 1.67. Calcium-deficient hydroxyapatite forms a stable invariant point with CaHPO₄ and a metastable invariant point with CaHPO₄. 2H₂O. Inspection of the diagram indicates that the compounds CaHPO₄ and CaPHO₄.2H₂O dissolve incongruently. Incongruent dissolution of either CaHPO₄ or CaHPO₄.2H₂O results in the formation of hydroxyapatite during the dissolution process. Such incongruency between these compounds and hydroxyapatite influences their microstructural relationships.     

Calculation of Phase Diagrams for the YO1.5—BaO—CuOx System

The thermodynamic data for the YO_1.5–BaO, BaO-CuO_x, and YO_1.5–CuO_x quasi-binary systems were optimized from experimental phase diagrams. They were used to calculate tentative phase diagrams for the YO_1.5–BaO—CuO_x quasi-ternary system. The equilibrim liquidus surface and the isothermal sections of the ternary system at 900°, 925°, 950°, 975°, and 1000°C were calculated. The isopleths containing YBa₂Cu₃O_7-δ were also calculated.     

Processing and Characterization of Thin Films of the Two-Layer Superconducting Phase in the Bi─Sr─Ca─Cu─O System: Evidence for Solid Solution

Thin films in the Bi─Sr─Ca─Cu─O system have been synthesized from liquid ethylhexanoate precursors by spin pyrolysis. An extensive solid-solution range was found for the two-Cu-layer phase through the study of c -axis-oriented, single-phase thin films fabricated on single-crystal, (100)-oriented, MgO substrates. All two-layer compositions were excess in Bi and deficient in Sr + Ca relative to the ideal 2212 composition and showed an overall cation deficiency. The solidus temperature and c lattice parameter were found to vary systematically with composition. Sharp superconductive transitions were obtained in the case of a number of different compositions with T _c varying between 72 and 84 K. Evidence for significant compositional heterogeneities within single-phase two-layer thin films was found and the implications for superconductivity are discussed. Compositions within the solid-solution range gave single-phase, c -axis-oriented films over a wide temperature range extending from 730°C to an upper, solidus (or peritectic) temperature (780° to 840°C) which is dependent on the initial starting composition. A model has been developed that describes the formation of the two-layer phase from a fugitive liquid.     

Characterization of C─B─N Solid Solutions Deposited from a Gaseous Phase between 900° and 1050°C

The composition, the structure, and some physical properties of boron–carbon–nitrogen solid solutions prepared by chemical vapor deposition (CVD) have been investigated. Both crystalline films and amorphous granular materials resulting respectively from heterogeneous and homogeneous nucleation were characterized by X-ray diffraction, XPS, RBS, and TEM. The compositions of these single-phase materials are gathered in two main domains located in the B/N > 1 part of the C─B─N composition diagram. It is stated that the carbon-rich domain results from structural disorder of an ideal C₅B₂N composition. The thermal behavior of these films indicates that no mass loss can be detected after 1 h at 1700°C but a graphitization and a formation of small amounts of B₁₃C₂ are observed. Density and preliminary electrical conductivity measurements were also performed.     

Processing and Characterization of Thin Films of the One-Layer Phase in the Bi-Sr-Ca-Cu-O System: Ca Solubility

Thin films in the Bi-Sr-Ca-Cu-O system have been synthesized from liquid ethyl hexanoate precursors by spin pyrolysis. The extension of the ternary one-layer phase field into the quaternary system has been determined through the replacement of Sr by Ca in single-phase, c -axis oriented thin films. A significant Ca solubility in the one-layer phase was found, the maximum being around 0.4 per 1 Cu. All onelayer compositions were excess in Bi and deficient in (Sr + Ca) relative to the ideal composition and showed over all cation deficiency. The c lattice parameter and solidus temperature were found to vary systematically with composition. The interpretation of the Ca solubility results in terms of Ca doping of the cation-deficient "Sr"sites and implications regarding the high- T_c Cu-layer phases in the system are discussed.     

Phase Equilibria in the Lead–Magnesium–Niobium–Oxygen System at 1000°C

Phase equilibria in the PbO–MgO–Nb₂O₅ system have been determined at 1000°C and 1 atm. A solid-solution range of the cubic pyrochlore phase was observed and the extent of that domain was determined. This solid solution equilibrates with the surrounding ternary and binary compounds to form a series of diphasic areas. The compatibility relations between all phases were determined except for a small domain where at least six lead niobate phases were stable within a very short range of compositions. The formation of pyrochlore impurities during the processing of Pb(Mg_1/3Nb_2/3)O₃ perovskite is discussed in relation to the phase diagram.     

Pseudo Phase Diagram and Microwave Dielectric Properties of Li2O–MgO–TiO2 Ternary System

Li₂O–MgO–TiO₂ ternary system is an important microwave dielectric ceramic material with excellent properties and prospect in both scientific research and application. A phase diagram of the Li₂O–MgO–TiO₂ ternary system was established in this article, based on earlier research results and our present work. Microwave dielectric properties with compositions in different regions of the phase diagram have been analyzed. We found that the 0.33 Li₂MgTi₃O₈–0.67 Li₂TiO₃ ceramics sintered at 1200°C exhibited excellent dielectric properties: Q × f value = 80 476 GHz (at 7.681 GHz), ε_r = 24.7, τ_f = +3.2 ppm/°C. We also designed two ceramic systems in the Li‐rich region of the Li₂O–MgO–TiO₂ ternary system, which received little attention in the past decades, because many excellent single‐phase ceramics, such as Li₂MgTiO₄, Li₂MgTi₃O₈ and MgTiO₃, have been found in the Ti‐rich region. The ceramic systems have low sintering temperatures but also relatively poor dielectric properties.     

Solid Phase Relations at 950°C in La-Ba-Cu-O

Subsolidus phase relations in the La₂O₃–BaO–CuO system were studied at 950°C. Three previously reported binary compounds exist (La₂CuO₄, BaLa₂O₄, and BaCuO₂) and five previously reported ternary phases occur (La_2-xBa_xCuO_4-(x/2)+δ, La_4-2xBa_2+2xCu_2-xO_10-2x, La_2-xBa_1+xCu₂O_6-(x-2), La_3-xBa_3+xCu₆O_14±δ, and La₄BaCu₅O_13+δ). Of the seven phases in the diagram, all but BaLa₂O₄, BaCuO₂, and La₄BaCu₅O_13+δ were shown to exhibit significant ranges of solubility. The diagram is important in that both >30 K (La_2-xBa_xCuO_4-(x/2)+δ) and >90 K (La_3-xBa_3+xCu₆O_14+δ, x=1) superconductors occur.     

茶碱、烟酰胺与异丙醇三元系统在298.15和308.15 K的相图研究

以茶碱、烟酰胺通过分子间氢键形成的共晶为例研究了共晶的热力学性质,测量了以异丙醇为溶剂茶碱 烟酰胺共晶在298.15和308.15 K 下的溶解度,同时测定了茶碱 烟酰胺共晶的溶度积（KSP）。通过对溶解度数据的分析表明茶碱 烟酰胺共晶在溶液中会形成1∶1的溶液络合,测定了溶液中共晶的溶度积及络合常数以及共晶组元对共晶溶解度的影响,同时考察了温度对溶度积和络合常数的影响。为了深入了解共晶在不同温度下的形成规律,绘制了在298.15和308.15 K茶碱 烟酰胺在异丙醇中的三元相图,分析了共晶的三元相图随温度的变化趋势,为药物共晶生产中目标产物的控制提供理论支持。     

Quaternary System U-C-O-N at 1700°C: Phase Relations in the Low-Nitrogen Region

Phase relations in the system U-C-O-N at 1700°C were established at nitrogen levels up to an atomic ratio N: C 1:3 by microstructural and X-ray analyses of sintered powder compacts. The extent of the solid-solution field of uranium oxycarbonitride was established on the ternary plane U-C_0.75No._0.25-O. The maximum solubility of oxygen in the solid solution is 14 at.%, corresponding to a composition U_0.50C_0.27O _0.14N_0.09 compared to 17 at.% on the U-C-O plane. Nine other phase fields were established on the U-C-O C_0.75N_0.25-O plane, all of which contain a uranium oxycarbonitride solid-solution phase and a gaseous phase of CO and N.₂. Equilibrium pressure varies from about 0.01 torr in phase fields containing free uranium to about 200 torr in the field containing solid solution +"UC₂" (oxy-gen-containing dicarbide) + C + UO₂. Lattice parameters of the solid-solution phase were determined. A field containing solid solution and UzC3 exists to about 3.5 at.% O and 2 at.% N at the hyperstoichiometric boundary of the solid-solution field. An isothermal phase diagram for the low-nitrogen region of the U-C-O-N system is proposed.     

The 1300°C Isothermal Section in the Ti–In–C Ternary Phase Diagram

In this paper we map out the 1300°C isothermal section in the Ti–In–C ternary system. Two ternary compounds exist: Ti₂InC_α and Ti₃InC_δ. At 1300°C TiC _x is in equilibrium with all phases, Ti₃InC_δ is in equilibrium with all the phases except C, and Ti₂InC is in equilibrium with all phases except Ti and C. The range of δ in Ti₃InC_δ varies from 0.95 to 0.8. A correlation was found between δ and the lattice parameters of this phase. The maximum solubilities of In and C in Ti are 14 and 4 at.%, respectively. Similarly, α in Ti₂InC_α varies from ≈0.85 to 1. The dissolution of ∼4±0.3 at.% In in TiC _x reduces the C concentration to ≈24 at.%. In the In-rich corner, a liquid region exists.     

High quality factor microwave dielectric ceramics in the (Mg1/3Nb2/3)O2–ZrO2–TiO2 ternary system

Novel high quality factor microwave dielectric ceramics (1?x)ZrTiO₄?x(Mg_1/3Nb_2/3)TiO₄ (0.325≤x≤0.4) and (ZrTi)_1?y(Mg_1/3Nb_2/3)_yO₄ (0.2≤y≤0.5) with the addition of 0.5 wt% MnCO₃ in the (Mg_1/3Nb_2/3)O₂–ZrO₂–TiO₂ ternary system were prepared, using solid‐state reaction method. The relationship between the structure and microwave dielectric properties of the ceramics was studied. The XRD patterns of the sintered samples reveal the main phase belonged to α‐PbO₂‐type structure. Raman spectroscopy and infrared reflectivity (IR) spectra were employed to evaluate phonon modes of ceramics. The 0.65ZrTiO₄?0.35(Mg_1/3Nb_2/3)TiO₄?0.5 wt% MnCO₃ ceramic can be well densified at 1240°C for 2 hours and exhibits good microwave dielectric properties with a relative permittivity (ε_r) of 42.5, a quality factor (Q×f) value of 43 520 GHz (at 5.9 Ghz) and temperature coefficient of resonant frequency (τ_f) value of ?5ppm/°C. Furthermore, the (ZrTi)_0.7(Mg_1/3Nb_2/3)_0.3O₄?0.5 wt% MnCO₃ ceramic sintered at 1260°C for 2 hours possesses a ε_r of 31.8, a Q×f value of 35 640 GHz (at 6.3 GHz) and a near zero τ_f value of ?5.9 ppm/°C. The results demonstrated that the (Mg_1/3Nb_2/3)O₂–ZrO₂–TiO₂ ternary system with excellent properties was a promising material for microwave electronic device applications.