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1.
Harumi Yokokawa Natsuko Sakai Teruhisa Horita Katsuhiko Yamaji Yueping Xiong Takanori Otake Hiroo Yugami Tatsuya Kawada Junichiro Mizusaki 《Journal of Phase Equilibria and Diffusion》2001,22(3):331-338
Phase diagram calculations that were made previously for the ZrO2-MO
m/2 (m = 2, 3, 4) systems and for the ZrO2-YO1.5-MO
m/2 (M = transition metals) systems have been extended to the ZrO2-YO1.5-CeO2(-CeO1.5) system to make an attempt to explain (1) thermogravimetric (TG) results as a function of oxygen potential, (2) electronic
conductivity as a function of oxygen potential, and (3) a miscibility gap observed in air. The interaction parameters for
the CeO2-CeO1.5-YO1.5 system were obtained from the reported oxygen nonstoichiometry in CeO2−x
and rate earth doped ceria, (Ce,RE)O2−δ
. The interaction parameters for the ZrO2-CeO2 subsystem were obtained so as to reproduce the observed miscibility gap at 1273 K. Those thermodynamic properties can reproduce
consistently the experimental behaviors of the electronic conductivity and the TG results in the (Zr1−x
Ce
x
)0.8Y0.2O1.9 solid solutions; these indicate the enhancement of reduction of CeO2. 相似文献
2.
S. Sodeoka M. Suzuki K. Ueno H. Sakuramoto T. Shibata M. Ando 《Journal of Thermal Spray Technology》1997,6(3):361-367
The thermal and mechanical properties of ZrC2-CeO
2plasma-sprayed coatings were evaluated to examine their potential as a thermal barrier coating. ZrO2-CeO2 solid-solution powders containing up to 70 mol % CeO2 are successfully plasma sprayed, but cerium content decreases during spraying due to the vaporization of cerium oxide. Hardness
is greatest at 30 mol% CeO2. With increased CeO2 content, the thermal conductivity decreases to 0.5 W/m K and the thermal expansion coefficient increases to 12.5 x 10-6 /K. Increased torch input power causes both the relative density and the hardness to increase monotonically, while the thermal
conductivity and the thermal expansion coefficient are not significantly affected. When heated above 1300 K, the coating shrinks
considerably due to sintering and its thermal conductivity increases abruptly. 相似文献
3.
4.
5.
Tiezhu Ding Luomeng Chao Wenliang Fan Jun Zhang 《Journal of Materials Engineering and Performance》2012,21(1):95-100
Perovskite oxide samples of (La1−x
Pr
x
)0.6Sr0.4Co0.8Fe0.2O3−δ (x = 0.2, 0.4, 0.6, 0.8) are obtained by solid-state reaction method. The oxygen chemical diffusion properties of (La1−x
Pr
x
)0.6Sr0.4Co0.8Fe0.2O3−δ are determined by electrical conductivity relaxation technique. The results show that the conductivity of (La1−x
Pr
x
)0.6Sr0.4Co0.8Fe0.2O3−δ increases with the increase of oxygen partial pressure. The (La1−x
Pr
x
)0.6Sr0.4Co0.8Fe0.2O3−δ samples have a high oxygen chemical diffusion coefficient, which decreases linearly with a decrease in temperature and an
increase in Pr content. The oxygen chemical diffusion coefficient D
chem remains fairly constant at high PO2. The oxygen chemical diffusion coefficient is the highest for (La1−x
Pr
x
)0.6Sr0.4Co0.8Fe0.2O3−δ with x = 0.2, and attains a value of 9.41 × 10−5 cm2 s−1 at 600 °C. This shows the material’s promise as a cathode material for intermediate temperature solid oxide fuel cells. 相似文献
6.
Effects of Sc doping on electrical conductivity of BaZrO<Subscript>3</Subscript> protonic conductors
BaZr1-xScxO3-0.5x (x=0.07,0.10,0.13,0.16) powders were prepared by solid-state reaction method,and ZnO was used as sintering aid.Samples with different amount of ZnO additive were sintered at 1450 ℃ for 6 h in air.Single cubic perovskite phase proton conductors were obtained.Conductivity was measured by electrochemical workstation.It was shown that Sc doping could increase conductivity through enhancing the carrier concentration in the material,but excessive Sc content might decrease the carrier concentration because of its charge compensation.ZnO had an influence on carrier concentration and mobility and affected the electrical conductivity.2 mol% ZnO and 13 mol% ScO1.5 doped sample showed the highest DC conductivity of 3.6 × 10-3 S·cm-1 tested at 800 ℃ in wet hydrogen atmosphere. 相似文献
7.
Phase relations in the system CaO-SrO-PbO-O2 at 1100 K have been determined by equilibrating samples with different compositions in air, oxygen, or evacuated ampoules
for 7 days and characterizing quenched specimens by optical and scanning electron microscopy, energy-dispersive analysis of
x-rays (EDX), and x-ray diffraction (XRD). There is a solid-state miscibility gap in the pseudo-binary system CaO-SrO, and
continuous solid solubility between Ca2PbO4 and Sr2PbO4 at 1100 K. Substitution of Ca for Sr occurs only to a limited extent (∼2 mol.%) in SrPbO3. The calcium-rich solid solutions (Ca1−y
Sr
y
)2PbO4 characterized by y≤0.255 are in equilibrium with PbO in air; compositions with y≥0.255 coexist with (Ca1−z
Sr
z
)PbO3. There is a three-phase region involving the two monoxide solid solutions (Ca1−x
Sr
x
)O on either side of the miscibility gap with x=0.24 and 0.71 and (Ca1−y
Sr
y
)2PbO4 with y=0.96. Accurately determined are the locations of tie-lines between the solid solutions. Attainment of equilibrium was checked
by the conventional tie-line rotation technique. The excess Gibbs energy of mixing of the solid solution with orthorhombic
structure is obtained by an analysis of tie-line data; for the mixing of one mole of Ca and Sr represented by (Ca1−y
Sr
y
)Pb0.5O2, ΔG
E
=y(1−y) [15,840−2950 y] J/mol. The thermodynamic properties suggest the onset of immiscibility in this solid solution below 884 (±5) K. The miscibility
gap is asymmetric with a critical composition at y=0.43 (±0.02). Inside the triangle (Ca1−y
Sr
y
)Pb0.5O2−(Ca1−z
Sr
z
)PbO3−PbO, a small liquid-phase region is present close to the PbO corner, surrounded by three two-phase fields. Each corner of
the approximately triangular liquid-phase region is associated with a three-phase field. 相似文献
8.
Phase relations in the system CaO-SrO-PbO-O2 at 1100 K have been determined by equilibrating samples with different compositions in air, oxygen, or evacuated ampoules
for 7 days and characterizing quenched specimens by optical and scanning electron microscopy, energy-dispersive analysis of
x-rays (EDX), and x-ray diffraction (XRD). There is a solid-state miscibility gap in the pseudo-binary system CaO-SrO, and
continuous solid solubility between Ca2PbO4 and Sr2PbO4 at 1100 K. Substitution of Ca for Sr occurs only to a limited extent (∼2 mol.%) in SrPbO3. The calcium-rich solid solutions (Ca1−y
Sr
y
)2PbO4 characterized by y≤0.255 are in equilibrium with PbO in air; compositions with y≥0.255 coexist with (Ca1−z
Sr
z
)PbO3. There is a three-phase region involving the two monoxide solid solutions (Ca1−x
Sr
x
)O on either side of the miscibility gap with x=0.24 and 0.71 and (Ca1−y
Sr
y
)2PbO4 with y=0.96. Accurately determined are the locations of tie-lines between the solid solutions. Attainment of equilibrium was checked
by the conventional tie-line rotation technique. The excess Gibbs energy of mixing of the solid solution with orthorhombic
structure is obtained by an analysis of tie-line data; for the mixing of one mole of Ca and Sr represented by (Ca1−y
Sr
y
)Pb0.5O2, ΔG
E
=y(1−y) [15,840−2950 y] J/mol. The thermodynamic properties suggest the onset of immiscibility in this solid solution below 884 (±5) K. The miscibility
gap is asymmetric with a critical composition at y=0.43 (±0.02). Inside the triangle (Ca1−y
Sr
y
)Pb0.5O2−(Ca1−z
Sr
z
)PbO3−PbO, a small liquid-phase region is present close to the PbO corner, surrounded by three two-phase fields. Each corner of
the approximately triangular liquid-phase region is associated with a three-phase field. 相似文献
9.
The thermal conductivities of [(ZrO2)1−x(CeO2)x]0.92(Y2O3)0.08 (0 ? x ? 1) solid solutions are studied in this paper. The incorporation of ZrO2 and CeO2 in the solid solution decreases the thermal conductivity compared with their end members (YSZ and YDC). The thermal conductivities of the solid solutions show clearly different temperature dependences in the ZrO2-rich (0 ? x ? 0.5) region and in the CeO2-rich region (0.5 ? x ? 1). The composition and the temperature dependence of the thermal conductivities are discussed based on established phonon scattering theories. We have concluded that the composition dependence of the thermal conductivity of this system is mainly controlled by the mass difference between Zr4+ and Ce4+, while the thermal conductivity-temperature relationship is dominated by the randomness of the defect distribution. 相似文献
10.
Songlin Li Lei Wang Yuming Xiong Gyuyeol Bae Changhee Lee 《Journal of Materials Engineering and Performance》2013,22(12):3717-3722
The coating formation in a kinetic spray process mainly depends on the impact of inflight particles at a high velocity. The plastic deformation at the impact interface would disrupt the native oxide scale on the particle and the substrate to generate the intimate contact of the atomic structures. Accordingly, it poses a challenge in producing ceramic coating during kinetic spray because of the lack of plasticity of ceramic powders at room temperature. In this study, we proposed to prepare ZrO2 ceramic coatings using partially amorphized powder with nanometer size in the kinetic spray process. To prepare the powder for the use of the kinetic spray, the amorphization and grain refinement of ZrO2 powder in mechanical ball milling were studied. The results showed that the amorphization and grain refinement were improved because of the formation of solid solution when the CeO2 agent was added. Subsequently, a nearly spherical powder was achieved via spray drying using the milled powders. The plasticity of the milled powders was tested in the kinetic spray process using Nitrogen as process gas. A dense ZrO2-CeO2 coating with a thickness of 50 μm was formed, whereas spraying milled ZrO2 powder can only lead to an inhomogeneous dispersion of the destructible particles on the surface of the substrate. 相似文献
11.
An examination of the ZrO2-YO1.5-TaO2.5 system reveals several promising attributes for use in thermal barrier coating applications. The rather unique presence of a stable, non-transformable tetragonal region in this ternary oxide system allows for phase stability to high temperatures (1500 °C). Selected compositions with high levels of yttria and tantala have also shown superior resistance to vanadate corrosion than the commercially utilized 7YSZ. In addition, Y + Ta stabilized zirconia compositions within the non-transformable tetragonal phase field exhibit toughness values comparable or somewhat higher than those of 7YSZ, which bodes well for their durability as TBCs. These promising attributes are discussed in this paper in the context of recent experimental work. 相似文献
12.
Susumu Imashuku Tetsuya Uda Yoshitaro Nose Yasuhiro Awakura 《Journal of Phase Equilibria and Diffusion》2010,31(4):348-356
Phase relationship of a BaO-ZrO2-YO1.5 system at 1500 and 1600 °C was examined in order to determine whether a phase separation at the composition of 15% yttrium-doped
barium zirconate exists. According to a pseudoternary phase diagram of the BaO-ZrO2-YO1.5 system established by this work, the solubility of yttria into cubic barium zirconate at 1600 °C is 0.25 in a mole fraction
of yttria
(X\textYO1.5 ) (X_{{{\text{YO}}_{1.5} }} ) . Thus, we confirmed that there is no phase separation at the composition of 15% yttrium-doped barium zirconate at 1600 °C.
On the other hand, at 1500 °C, there might be a phase separation at the composition of 15% yttrium-doped barium zirconate
into yttrium-doped barium zirconate where quite small amount of yttrium is doped and a new phase whose composition is close
to reported BZ(II) phase. 相似文献
13.
Superfine cerium-zinc oxides Ce1-xZnxO2-x with x = 0, 0.1, 0.3, 0.5, and 1.0 were obtained by grinding Ce(SO4)2·4H2O, ZnSO4·7H2O and NH4HCO3 under the condition of surfactant PEG-400 being present at room temperature, washing the mixture with water to remove soluble inorganic salts, drying at 80°C, and calcining.The precursor and its calcined samples were characterized using thermogravimetry and differential thermal analyses(TG/DTA), UV-vis absorption spectroscopy, X-ray powder diffraction(XRD), and scanning electron microscopy(SEM).The results showed that superfine Ce1-xZnxO2-x behaved as an excellent UV-shielding material.The ZnO-doped CeO2 can facilitate the formation of crystalline state CeO2.The catalytic ability of products used in air oxidation of castor oil was investigated.The results showed that the catalytic abilities of products decreased with increasing zinc amount. 相似文献
14.
ZHANG Hongsong SUN Kun XU Qiang WANG Fuchi LIU Ling WEI Yuan CHEN Xiaoge 《稀有金属(英文版)》2009,28(3):226-230
Sm2(Zr1−x
Ce
x
)2O7 (x = 0.1, 0.2, and 0.3) ceramics were prepared by solid reaction method at 1600°C for 10 h using Sm2O3, ZrO2, and CeO2 as starting reactants. The phase compositions, microstructures, thermal expansion coefficients, and partial thermal conductivities
of these materials were investigated. X-ray diffraction (XRD) results reveal that Sm2(Zr0.9Ce0.1)2O7 with pyrochlore structure and Sm2(Zr1−x
Ce
x
)2O7 (x = 0.2 and 0.3) with fluorite structure were synthesized, and scanning electrical microscopy (SEM) images show that the microstructures
of these products are very dense. The linear thermal expansion coefficients increase with increasing temperature in the temperature
range from ambient to 1200°C, and the thermal expansion coefficients increase with increasing content of doped CeO2. The thermal conductivities of Sm2(Zr0.8Ce0.2)2O7 and Sm2(Zr0.7Ce0.3)2O7 decrease gradually with an increase in temperature. These results show that the synthesized ceramic materials can be explored
as novel prospective candidate materials for use in new thermal barrier coating systems in the future. 相似文献
15.
Jiaxiu Guo Dongdong Wu Lei Zhang Maochu Gong Ming Zhao Yaoqiang Chen 《Journal of Alloys and Compounds》2008,460(1-2):485-490
A kind of nanometric CeO2–ZrO2–Nd2O3 (CZN) solid solution for a carrier in the automotive three-way catalysts was synthesized by a coprecipitation method and characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption (BET), scanning electron microscopy (SEM) and oxygen storage capacity (OSC). For the purpose of comparison, an unincorporated CeO2–ZrO2 (CZ) was also synthesized. The XRD measurements disclose the prepared CeO2–ZrO2–Nd2O3 have a face-centered cubic fluorite structure and nanoparticle sizes. According to the results of XPS, Nd3+ ions can enter the CZ lattice and form a homogenous solid solution. Oxygen storage capacity measurements reveal that CeO2–ZrO2–Nd2O3 display high oxygen mobility at a low temperature. The results of the activity tests show that the catalyst exhibits good three-way catalytic activity and fairly wide range of air-to-fuel ratios. 相似文献
16.
Fatma Meydaneri Mehtap Payveren Buket Saatçi Mehmet Özdemir Necmettin Maraşlı 《Metals and Materials International》2012,18(1):95-104
The grain boundary groove shapes for Zn solid solution in equilibrium with Sn-Zn eutectic liquid were observed with a radial
heat flow apparatus. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient, the solid-liquid and the
grain boundary energy for the Zn solid solution in equilibrium with Sn-Zn eutectic liquid were determined to be (2.32 ± 0.13)×10−8 Km, (120.87 ± 13.29)×10−3 J.m−2 and (194.76 ± 23.37)×10−3 J.m−2, respectively. The termal conductivity of the eutectic Sn-9 wt% Zn solid solution, κ
S
, was obtained as 74.74 W/Km by using a radial heat flow apparatus. The thermal conductivity ratio of the eutectic liquid
to the eutectic solid, R = κ
L
/κ
S
was found to be 0.58 with a Bridgman-type directional growth apparatus. Thus, the value of the thermal conductivity of eutectic
Sn-9 wt% Zn liquid solution, κ
L
, was obtained as 43.82 W/Km. 相似文献
17.
Sm3+-doped Ce1−xSmxO2−δ (0.05 ≤ x ≤ 0.3) nano-sized powders for solid electrolytes were synthesized by a solution combustion method, using aspartic
acid as a combustion fuel. The calcined Ce1−xSmxO2−δ powders were a ceria-based single phase with a cubic fluorite structure. The nano-sized Ce1−xSmxO2−δ powders provided a high density, ultra-fine grain size, and high electrical conductivity even at a low sintering temperature
of 1400 °C. The grain size and relative density of the Ce1−xSmxO2−δ pellets ranged from 329 nm to 496 nm and from 91.9 % to 99.2 %, respectively. The grain size and density of the Ce1−xSmxO2−δ pellets decreased with an increase of Sm3+ content. The electrical conductivity of the Ce1−xSmxO2−δ increased with an increase of Sm3+ content up to x = 0.25 and then decreased with higher Sm3+ content. The maximal electrical conductivity (0.105 Scm−1) was obtained with Ce0.75Sm0.25O2−δ at 800 °C. 相似文献
18.
Jinjing Du Yihan Liu Guangchun Yao Zhongsheng Hua Xiuli Long Bin Wang 《Journal of Materials Engineering and Performance》2013,22(6):1776-1782
NiO-Fe2O3-ZrO2f composites were fabricated by a two-step sintering process. No phase transformation for ZrO2f was observed. The as-prepared NiO-Fe2O3-ZrO2f ceramic showed excellent mechanical properties because of the introduction of ZrO2 fiber. The values for both the bending strength and fracture strength of 3 wt.% ZrO2f-reinforced NiFe2O4 samples reached the maximum values of ~89.0 MPa and ~4.67 MPa m1/2, respectively, The toughness mechanism is mainly attributed to fibers’ fracture, crack deflection, fibers’ pull-out, and fibers’ debonding. The conductivity of ZrO2f-reinforced NiFe2O4 is dependent on temperature and ZrO2f content. When the electrolytic temperature is up to 950 °C, the conductivity value of the sample reinforced with 4 wt.% ZrO2 fibers is 0.63 S/cm, which has been improved by 37.8% compared with the conductivity value of 0.45 S/cm for the un-doped samples. The main conductive mechanisms of ZrO2 fiber in the matrix are the one based on the substitution of Zr4+ ions to produce quasi-free electrons, and the other based on oxygen ionic conducting mechanism. 相似文献
19.
The powder X-ray diffraction patterns of LaFe11.5Si1.5 compounds annealed at different high temperatures from 1323 K (5 h) to 1623 K (2 h) show that a large amount of 1:13 phase begins to form in LaFe11.5Si1.5 compound annealed at 1423 K (5 h). In the temperature range from 1423 to 1523 K, α-Fe and LaFeSi phases rapidly decrease to form 1:13 phase. LaFeSi phase is rarely observed, and the most amount of 1:13 phase is obtained in the compound annealed at 1523 K (5 h). With the annealing temperature increasin... 相似文献
20.
The evolution of lattice structure and thermal conductivity has been studied systematically for a range of Ti-doped, Y2O3-stabilized ZrO2 (YSZ) solid solutions. The mechanism of reducing the thermal conductivity by Ti doping has been determined. Ti4+ mainly substitutes for Zr4+ below a critical composition factor (x ? 0.08), above which the interstitial Ti4+ need to be considered separately. The effect of lattice defects caused by mass and radius differences between Ti4+ and Zr4+ ions on the phonon scattering coefficient was discussed quantitatively. And the reduction of oxygen vacancy by interstitial Ti4+ ions which increases the thermal conductivity at high Ti doping content was also determined. Concerning the integrated phase stability and thermo-mechanical properties, Ti-doped YSZ is believed to be a promising candidate for thermal barrier coatings at higher temperature. 相似文献