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1.
《Journal of the European Ceramic Society》2020,40(12):4184-4190
Materials based on CeO2–La2O3–Er2O3 system are promising candidates for a wide of applications, but the phase relationship has not been studied systematically previously. To address this challenge, the isothermal section of the phase diagram for 1500 °C was investigated. The phase relations in the CeO2–La2O3–Er2O3 ternary system at 1500 °C were studied by X-ray diffraction and scanning electron microscopy in the overall concentration range. To study phase relationships at 1500 °C the as-repared samples were thermally treated in two stages: at 1100 °C (for 300 in air) and then at 1500 °C (for 70 h in air) in the furnaces with heating elements based on Fecral (H23U5T) and Superkanthal (MoSi2), respectively. The solid solutions based on various polymorphous forms of constituent phases and with perovskite-type structure of LaErO3 (R) with orthorhombic distortions were revealed in the system. No new phases were found. The isothermal section of the phase diagram for the CeO2–La2O3–Er2O3 system has been constructed. It was established that in the ternary CeO2–La2O3–Er2O3 system there exist fields of solid solutions based on hexagonal (A) modification of La2O3, cubic modification of CeO2 with fluorite-type structure (F), cubic modification Er2O3 and with perovskite-type structure of LaErO3 (R) with orthorhombic distortions. The maximal solubility of ceria in LaErO3 was found to be around ∼ 2 mol% CeO2 along the section CeO2–(50 mol % La2O3 –50 mol% Er2O3). 相似文献
2.
《Journal of the European Ceramic Society》2020,40(3):751-758
Materials based on CeO2-Eu2O3 system are promising candidates for a wide range of applications, but the phase relationship has not been studied systematically previously. To address this challenge, the subsection of the phase diagram for 600, 1100 and 1500 °C has been elucidated. Samples of different compositions have been prepared from nitrate acid solutions using conventional ceramic techniques; evaporation, drying, and calcinations. The phase relations in the binary CeO2-Eu2O3 system at 600–1500 °C in air were studied from the heat treated samples using X-ray diffraction analysis, polarized light microscopy investigation and scanning electron microscopy in the overall concentration range. It was established that in the binary CeO2-Eu2O3 system there exist fields of solid solutions based on monoclinic (B) modification of Eu2O3, cubic (C) modification of Eu2O3 and cubic modification of CeO2 with fluorite-type structure (F). The systematic study that covered whole composition range excluded formation of new phases. The refined lattice parameters of the unit cells and the boundaries of the homogeneity fields for solid solutions were determined. 相似文献
3.
O.A. Kornienko O.R. Andrievskaya O.I. Bykov A.V. Samelyuk Yu. M. Bataiev 《Journal of the European Ceramic Society》2021,41(6):3603-3613
According to the results of the samples studied by X-ray diffraction and microstructural analyzes the phase equilibria in the binary La2O3 – Sm2O3 and ternary ZrO2 – La2O3 – Sm2O3 systems were studied. The boundaries of the phase fields of the binary system are specified and an isothermal cross section of the ternary state diagram of the ZrO2 – La2O3 – Sm2O3 system at a temperature of 1500 °C is constructed. No new phases have been identified in the studied systems. It is established that in the ternary system ZrO2 – La2O3 – Sm2O3 at 1500 °C fields of solid solutions on the basis of cubic (F) modification with structure of fluorite type, tetragonal (T) modification of ZrO2, monoclinic (B) modifications of Sm2O3, hexagonal (A) are formed. La2O3, as well as an ordered phase with a structure of the type of pyrochlore Ln2Zr2O7 (Py). The boundaries of the phase fields and the parameters of the unit cells of the formed phases are determined. A characteristic feature of this isothermal cross section is the formation of a continuous series of solid solutions based on the phase of the pyrochlore type La2Zr2O7 (Sm2Zr2O7). The limiting solubility of Sm2O3 in the ordered phase La2Zr2O7 is 16 mol. % along the section Sm2O3- (67 mol.% ZrO2 - 33 mol.% La2O3). The solubility of La2O3 in the solid solution Sm2Zr2O7 is slightly less and is 11 mol. % along the section La2O3- (67 mol.% ZrO2 - 33 mol.% Sm2O3). The isothermal cross-section of the state diagram of the ZrO2 – La2O3 – Sm2O3 system at 1500 °C is characterized by the presence of three three-phase (Py + T + F), (A + Py + B), (Py + F + B) and eight two-phase (A + Py), (B + A), (B + Py), (F + B), (T + F), (Py + T), (F + Py-two) areas. 相似文献
4.
《Ceramics International》2017,43(6):4930-4936
A complete subsolidus ternary phase diagram of the Bi2O3-CuO-Nb2O5 (BCN) system was constructed. Careful firing control and phase analysis were applied to determine the phase assemblages and compatibilities over a wide range of temperatures, i.e. 700–925 °C. Phase-pure BCN pyrochlores were found to crystallise in cubic symmetry, space group Fd3m, No. 227 with lattice constants in the range of 10.4855 (5)<x<10.5321 (3). The mechanism of this limited subsolidus series could be represented by a general formula, Bi3.08−xCu1.84+2x/9Nb3.08+7x/9O14.16+6x/9 (0≤x≤0.36) wherein the reduction in Bi content was compensated by a proportion amount of copper and niobium together with non-stoichiometry in oxygen. 相似文献
5.
E.R. Andrievskaya O.A. KornienkoA.V. Sameljuk A. Sayir 《Journal of the European Ceramic Society》2011,31(7):1277-1283
Materials based on CeO2-La2O3 system are promising candidates for a wide range of applications, but the phase relationship has not been studied systematically previously. To address this challenge, the subsection of the phase diagram for 1100 and 1500 °C have been elucidated. Samples of different compositions have been prepared from nitrate acid solutions using conventional ceramic techniques; evaporation, drying, and calcinations. The phase relations in the binary CeO2-La2O3 system at 1100-1500 °C were studied from the heat treated samples using X-ray diffraction analysis, petrographic investigation and scanning electron microscopy in the overall concentration range. It was established that in the binary CeO2-La2O3 system there exist fields of solid solutions based on hexagonal (A) modification of La2O3, and cubic modification of CeO2 with fluorite-type structure (F). The systematic study that covered whole composition range excluded formation of new phases. The refined lattice parameter of the unit cell and the boundaries of the homogeneity fields for solid solutions were determined. 相似文献
6.
Phase equilibria of the ZnO–SiO2, Al2O3–SiO2 and ZnO–Al2O3–SiO2 systems at liquidus were characterized at 1340–1740 °C in air. The ZnO–Al2O3 subsolidus phase equilibria were derived from the experiments with the SiO2- and CaO + SiO2-containing slags. High-temperature equilibration on silica or platinum substrates, followed by quenching and direct measurement of Zn, Al, Si and Ca concentrations in the phases with the electron probe X-ray microanalysis (EPMA) was used to accurately characterize the system. Special attention was given to zincite phase that was shown to consist of two separate ranges of compositions: round-shaped low-Al zincite (<2 mol.% AlO1.5) and platy high-Al zincite (4–11 mol.% AlO1.5). A technique was developed for more accurate measurement of the ZnO solubility in the low-ZnO phases (corundum, mullite, tridymite and cristobalite) surrounded by the ZnO-containing slag, using l-line for Zn instead of K-line, avoiding the interference of secondary X-ray fluorescence. Solubility of ZnO was found to be below 0.03 mol.% in corundum and cristobalite, and below 0.3 mol.% in mullite. Present experimental data were used to obtain a self-consistent set of parameters of the thermodynamic models for all phases in this system using FactSage computer package. The modified quasichemical model with two sublattices (Zn2+, Al3+, Si4+) (O2?) was used for the liquid slag phase; the compound energy formalism was used for the spinel (Zn2+,Al3+)[Zn2+,Al3+,Va]2O2-4 and mullite Al3+2(Al3+,Si4+) (O2?,Va)5 phases; the Bragg-Williams formalism was used for the zincite (ZnO, Al2O3); other solid phases (tridymite and cristobalite SiO2, corundum Al2O3, and willemite Zn2SiO4) were described as stoichiometric. Present study is a part of the research program on the characterization of the multicomponent Pb–Zn–Cu–Fe–Ca–Si–O–S–Al–Mg–Cr–As–Sn–Sb–Bi–Ag–Au–Ni system. 相似文献
7.
《Ceramics International》2020,46(15):23534-23543
This paper reports on the experimental investigation of the phase relations in the CaO-SiO2-Dy2O3 system. CaO-SiO2-Dy2O3 slags were equilibrated at 1773 and 1873 K for 86400 s in Ar and then quenched in water to determine the phase relations of the system. The composition of the equilibrated phases was measured by EPMA-WDS and XRD. The presence of ternary compounds and the solid solution and liquid regions were determined to construct the isothermal sections at 1773 and 1873 K of the ternary phase diagram. The data from this work will support further investigations on the feasibility to recover REEs through pyrometallurgical processing. 相似文献
8.
《Journal of the European Ceramic Society》2017,37(2):787-800
A critical assessment and thermodynamic optimization of phase diagrams and thermodynamic properties of the entire Na2O–FeO–Fe2O3–Al2O3–SiO2 system were carried out at 1 atm total pressure. A set of optimized model parameters obtained for all phases present in this system reproduces available and reliable thermodynamic property and phase equilibrium data within experimental error limits from 298 K to above liquidus temperatures for all compositions and oxygen partial pressures from metallic Fe saturation to 1 atm. The Gibbs energy of liquid solution was described based on the Modified Quasichemical Model considering the possible formation of NaAlO2 and NaFeO2 associates in the liquid state. The solid solutions wüstite, spinel, feldspar, nepheline, carnegieite, mullite, corundum, clino-pyroxene, meta-oxides and Na-β″-alumina were treated within the framework of Compound Energy Formalism. The database of model parameters can be used to calculate any thermodynamic property and phase diagram section of the present system. 相似文献
9.
《Journal of the European Ceramic Society》2021,41(14):7035-7043
High-temperature phase relations in the La2O3–TiO2–Nb2O5 ternary system were investigated at 1290 °C using SEM, EDS and XRD, and a subsolidus phase equilibrium diagram was constructed. It was demonstrated that the addition of the La1/3NbO3 to the La2O3:3TiO2 mixture completely stabilizes a perovskite-La2/3TiO3 compound, which is otherwise not stable at stoichiometric composition. On the other hand, a mixture La2O3:TiO2 =1:3 dissolves in La1/3NbO3 up to 15 mol% TiO2. Moreover, a newly defined composition of compound La30Ti16Nb4O87 formed in the La2O3-rich part of the system and a solid solution La3Ti5Nb10O39.5–La2Ti2Nb8O27 were proposed. In the binary subsystem LaTiNbO6-La0.462Ti0.386Nb0.614O3, the components exhibit opposite temperature dependence of resonant frequency in the microwave frequency range. Thus, the dielectric properties of the prepared ceramics can be tailored by varying the component concentration and thermally stable dielectric properties can be achieved for a composition with a LaTiNbO6/La0.462Ti0.386Nb0.614O3 molar ratio of 0.27. 相似文献
10.
Libin Zhuang Xiao Huang Yang Lu Jiawen Tang Yongjian Zhou Xin Ao Yan Yang Bingbing Tian 《Ceramics International》2021,47(16):22768-22775
Cubic phase garnet-type Li7La3Zr2O12 (LLZO) is a promising solid electrolyte for highly safe Li-ion batteries. Al-doped LLZO (Al-LLZO) has been widely studied due to the low cost of Al2O3. The reported ionic conductivities were variable due to the complicated Al3+-Li+ substitution and LixAlOy segregation in Al-LLZO ceramics. This work prepared Li7?3xAlxLa3Zr2O12 (x = 0.00~0.40) ceramics via a conventional solid-state reaction method. The AC impedance and corresponding distribution of relaxation times (DRT) were analyzed combined with phase transformation, cross-sectional microstructure evolution, and grain boundary element mapping results for these Al-LLZO ceramics to understand the various ionic transportation levels in LLZO with different Al-doping amounts. The low conductivity in low Al-doped (0.12~0.28) LLZO originates from the slow Li+ ion migration (1.4~0.25 μs) in the cubic-tetragonal mixed phase. On the other hand, LiAlO2 and LaAlO3 segregation occur at the grain boundaries of high Al-doped (0.40) LLZO, resulting in a gradual Li+ ion jump (6.5 μs) over grain boundaries and low ionic conductivity. The Li6.04Al0.32La3Zr2O12 ceramic delivers the optimum Li+ ion conductivity of 1.7 × 10?4 S cm?1 at 25 °C. 相似文献
11.
Xiaojun Luo Rong Wang Jun Ni Jianxin Lin Bingyu Lin Xianming Xu Kemei Wei 《Catalysis Letters》2009,133(3-4):382-387
A series of CeO2-La2O3 supported ruthenium catalysts were prepared by co-precipitation method and the as-obtained samples were characterized by N2 physisorption, X-ray diffraction, CO chemisorption, H2-TPR, H2-TPD and XPS. The activity test shows that ammonia concentration of the catalyst with 10% La is 13.9% at 10 MPa, 10,000 h?1, 450 °C, which is 17% higher than that of Ru/CeO2. La doping can improve the activity of Ru-ceria catalyst for ammonia synthesis by facilitating the reduction of oxygen which subsists in the cerium oxide surface. In addition, it can be realized that the test of catalyst stability proves the stability performance of Ru/CeO2-La2O3 catalyst within the reaction time of 55 h. 相似文献
12.
Wenke Zhi Fei Wang Bin Yang Tao Qu Yong Deng Yang Tian Jinyang Zhao 《Journal of the American Ceramic Society》2019,102(5):2863-2870
We investigated the isothermal section of the CaO-Al2O3-Sc2O3 ternary system at 1773 and 1873 K for 24 hours in Ar, and quenched in water to determine the operative phase equilibrate. The composition of the phases in equilibrium was determined by electron probe microanalysis. The isothermal section phase diagram of two temperature points (1773 and 1873 K) is obtained. The 1773 K isothermal section consists of one liquid compound (L), six binary compounds (CaO+L, Ca2Sc6Al6O20+L C3A+L, CaO.Sc2O3+L, CA+L, Ca2Sc6Al6O20+Sc2O3) and seven ternary compounds (Ca2Sc6Al6O20+Sc2O3+CA6, Ca2Sc6Al6O20+Sc2O3+L, Ca2Sc6Al6O20+CA+L, Ca2Sc6Al6O20+CA2+CA, Ca2Sc6Al6O20+CA2+CA6, CaO.Sc2O3+L+Sc2O3, C3A+CaO+L). At 1873 K, we found one liquid compound (L), five binary compounds (CaO+L, Ca2Sc6Al6O20+L, CaO.Sc2O3+L, CA+L, Ca2Sc6Al6O20+Sc2O3) and six ternary compounds (Ca2Sc6Al6O20+Sc2O3+CA6, Ca2Sc6Al6O20+Sc2O3+L, Ca2Sc6Al6O20+CA+L, Ca2Sc6Al6O20+CA2+CA, Ca2Sc6Al6O20+CA2+CA6, CaO.Sc2O3+L+Sc2O3) to exist at the isothermal section. The experimental information obtained in the present work not only is essential for the thermodynamic assessment of the CaO-Al2O3-Sc2O3 ternary system, but also is important for further investigation on separation of rare earths from metallurgical slags and rare-earth recovery. 相似文献
13.
Simple mathematical models for binary and ternary ion exchange equilibria were developed to predict selectivity coefficients and resin capacities from a simple experiment to within acceptable engineering accuracy limits. Batch equilibrium experimental investigations were undertaken to test the models for binary systems (Ni-Na, Cu-Na, Zn-Na, Cd-Na and Pb-Na) and ternary systems (Ni-Cu-Na, Cd-Ni-Na, Cd-Cu-Na and Pb-Cu-Na) with a commercial DOWEX HCR-W2 resin. Binary parameters were used to predict ternary equilibria. It was found that good agreement between the predicted and experimental values was obtained when the binary selectivity coefficients of the two competing heavy metal ions in the ternary system were either almost equal or differed by a factor as large as five. 相似文献
14.
建立了1套连续式热力学平衡测量装置,在压力1.5~10 MPa,温度303~343 K范围内,测量了H_2和CO_2在甲苯中的二元系平衡溶解度数据。结果表明,2种气体在甲苯中的溶解度均随压力增大而增加。H_2在甲苯中的溶解度随温度升高而增大。CO_2在甲苯中的溶解度则随温度升高而减小。考虑1个二元相互作用参数,将实验数据用Peng-Robinson状态方程式进行关联,可以获得满意的计算精度。 相似文献
15.
16.
《Journal of the European Ceramic Society》2014,34(7):1741-1753
Among the family of temperature-compensated microwave dielectric ceramics, BaMg1/3Ta2/3O3 shows the lowest dielectric loss and remains a material of choice for state-of-the-art airborne and land-based communication systems. We report on the compositional stability range, microwave dielectric properties, and the degree of atomic order of the title compound within the BaO–MgO–Ta2O5 ternary diagram. In most cases an atomic order is robust to the deviation from stoichiometry with an exception of Ba-rich and/or Ta-deficient samples which favor (partial) disorder. We further demonstrate that the dense, atomically ordered BaMg1/3Ta2/3O3 ceramic shows large variation of dielectric loss within a single phase composition region – a clear message that the dielectric loss in practical ceramics is dominated by extrinsic sources and that the cation order alone is insufficient to achieve a minimum dielectric loss in BaMg1/3Ta2/3O3. The low-temperature dielectric relaxation studies suggest that the extrinsic dielectric loss in the title compound is due to the ‘rattling’ of the off-centered Mg2+ ions misplaced at the Ba sites. Controlled deviation from the BaMg1/3Ta2/3O3 stoichiometry toward the Mg-deficient region leads to suppression of the extrinsic dielectric loss as a result of the reduced chemical activity of Mg ion. 相似文献
17.
《Journal of the European Ceramic Society》2014,34(6):1511-1522
The limited scheelite type Cd1−3x□xGd2xMoO4 solid solution, where 0 < x ≤ 0.25 and □ are cationic vacancies have been successfully synthesized by high-temperature annealing of CdMoO4/Gd2(MoO4)3 mixtures composed of 50.00 mol.% and less of Gd2(MoO4)3. The obtained materials as well as CdMoO4 and Gd2(MoO4)3 were characterized by powder XRD, DTA–TG, DSC, and SEM techniques. A phase diagram of the pseudobinary CdMoO4–Gd2(MoO4)3 system was constructed. The eutectic point corresponds to 1350 ± 5 K and ∼70.00 mol.% of Gd2(MoO4)3 in an initial CdMoO4/Gd2(MoO4)3 mixture. With decreasing of Gd3+ amount in the crystal lattice of CdMoO4, a melting point of the Cd1−3x□xGd2xMoO4 solid solution increases from 1351 (x = 0.25) to 1408 K (x = 0). EPR method was used to identify the paramagnetic Gd3+centers in Cd1−3x□xGd2xMoO4 for different values of x parameter as well as to select biphasic samples containing both Cd0.2500□0.2500Gd0.5000MoO4 and Gd2(MoO4)3. 相似文献
18.
The solid–liquid equilibria(SLE)for binary and ternary systems consisting of N-Vinylpyrrolidone(NVP),2-Pyrrolidone(2-P)and water are measured.The phase diagrams of NVP(1)+2-P(2),NVP(1)+water(2),NVP(1)+2-P(2)+1 wt%water(3)and NVP(1)+2-P(2)+2 wt%water(3)are identified as simple eutectic type with the eutectic points at 263.75 K(x_(1E)=0.5427),251.65 K(x_(1E)=0.3722),260.25 K(x_(1E)=0.5031)and256.55 K(x_(1E)=0.4684),respectively.The phase diagram of 2-P(1)+water(2)has two eutectic points(x_(1E)=0.1236,T_E=259.15 K and x_(1E)=0.7831,T_E=286.15 K)and one congruent melting point(x_(1C)=0.4997,T_C=303.55 K)because of the generation of a congruently melting addition compound:2-P·H_2O.The ideal solubility and the UNIFAC models were applied to predict the SLE,while the Wilson and NRTL models were employed in correlating the experimental data.The best correlation of the SLE data has been obtained by the Wilson model for the binary system of NVP+2-P.The UNIFAC model gives more satisfactory predictions than the ideal solubility model. 相似文献
19.
Yongdong Yu Fengyu Lin Yongting Zheng Wanjun Yu Xudong Liu YuChen Yuan Hang Yin Xiaodong He 《Journal of the European Ceramic Society》2021,41(10):5269-5279
Al2O3/ZrO2 supersaturated solid solution micro-powders (AZ-SSP) with three components were successfully obtained by combustion synthesis assisted rapid water cooling, and their nanoprecipitation mechanism and microstructure evolution were studied by phase field simulation and hot-press sintering. The results show that AZ-SSP could be used to fabricate Al2O3/ZrO2 nanocomposite ceramics (AZNC) with intragranular-intercrystalline microstructures by high-density nanoprecipitation, consistent with microstructures of heat-treated AZ-SSP via the phase field simulation. There were three simulated nanostructures of spherical and elongated particles in A57Z-SSP or A15Z-SSP and interlocking structures in A36Z-SSP. The submicro-crystals of A57ZNC and A15ZNC contain high-density nano- and supra-nano-particles, and the fracture toughness of these two ceramics can reach up to 10.37 ± 0.37 MPa·m1/2 and 12.63 ± 0.36 MPa·m1/2, respectively. Hence, the preparation method of ultra-fine structures by supersaturated solid solution has far-reaching guiding significance for various nanoceramics. 相似文献
20.
Rainer Telle 《Journal of the European Ceramic Society》2019,39(13):3677-3683
The quasi-ternary TiB2-CrB2-WB2 and the related quasi-binary subsystems were investigated by means of hot pressing and pressureless dilatometry in the temperature range between 1650 and 1900 °C. Long-term annealing up to 14 h was necessary for equilibration. Thus, samples were obtained first by densification and then by subsequent cooling to the respective temperature with continuous annealing for up to 16 h in some cases.In all binary subsystems the low-temperature range of the solidus and the liquidus lines could be determined. The CrB2-WB2 and the TiB2-WB2 systems are of eutectic type while the CrB2-TiB2 shows a continuous solid solubility.Furthermore, the miscibility gap proposed earlier for the CrB2-TiB2 could not be proven. The borders of the large homogeneity range of the AlB2-type (Ti,W,Cr)B2 solid solution were described. The presence of less than 5 mol% of CrB2 aids accommodating W into the AlB2-structure which agrees with previous sintering studies very well. Within the ternary composition range no indication for a ternary eutectic was found up to 1900 °C. Implications of impurities to the obtained phase diagrams are discussed. 相似文献