Ionic conductivity of Li8 − 2x Sr x ZrO6

Li_{8 − 2x} Sr _x ZrO₆ solid solutions have been synthesized, and their transport properties (electronic conductivity, temperature and composition dependences of their conductivity, and activation energy for conduction) have been studied using impedance spectroscopy. The results demonstrate that partial strontium substitution for lithium increases the conductivity of the materials relative to undoped Li₈ZrO₆.     

The ZrO2-rich region of the ZrO2-MgO system

The solubility limits of MgO in tetragonal zirconia were studied by combining the differential thermal analysis data and X-ray disappearing phase method. From these experiments a eutectoid reaction, tetragonal ZrO₂ solid solution monoclinic ZrO₂ solid solution + MgO, at 1120±10 °C and 1.6±0.2 mol% MgO was established. The solubility of MgO in tetragonal ZrO₂ diminished as the temperature increased, and at 1700 °C the solubility was less than 0.5 mol% MgO. The extent of the cubic zirconia solid solution single field was determined by using precise lattice parameter measurements and SEM observations. In this way an invariant eutectoid point, cubic ZrO₂ solid solution tetragonal ZrO₂ solid solution + MgO, was located at 1420±10 °C and 14.8±0.5 mol% MgO.     

Solid solutions of metastable tetragonal ZrO2 and Ce3ZrO8 in the system ZrO2-CeO2

In the system ZrO₂-CeO₂, metastable t-ZrO₂ solid solutions containing up to 30 mol% CeO₂ crystallize at temperatures of 385–430 °C from amorphous materials prepared by the hydrazine method. Crystalline Ce₃ZrO₈ solid solutions are formed in as-prepared powders between 30–75 mol % CeO₂. The variation of the lattice parameters of both solid solutions is determined as a function of CeO₂ content. The value of the lattice parameter of pure Ce₃ZrO₈ (cubic) is a = 0.5342 nm. Detailed characterization of the Ce₃ZrO₈ powder has been performed. Crystallite size and particle size are strongly dependent on the heating temperature. Specific surface areas do not drop below 40 m²g^–1 until the heating temperature is above 1000°C.     

Thermodynamic Assessment of the ZrO2—CeO2 and ZrO2—CeO1.5 Binary System

An optimal set of thermodynamic parameters of the ZrO2-CeO1.5 system has been obtained using phase diagram data by modern CALPHAD (CAL culation of PHAse Diagrams) technique.The liquid and other solid solution phases were regarded as substitutional solution.The ordered ZrCe2O7 phase was treated as a stoichiometric compound.The ZrO2-CeO2 system has been re-optimized with new reference state.A comparison between the ZrO2-CeO2 system and ZrO2-CeO1.5 system has been made through calculation.With the calculation, the experimental information is well reproduced and a good agreement is obtained.     

Synthesis of dispersed ZrO2 nano-laminae composed of ZrO2 nanocrystals

Dispersed ZrO₂ nano-laminae were synthesized at low temperature using zirconium oxynitrate and polyvinyl pyrrolidone (PVP) as reaction materials. High-resolution transmission electron microscopy (HRTEM) of individual ZrO₂ nano-laminae showed that each piece of ZrO₂ nano-laminae was assembled by large numbers of ZrO₂ nanocrystals. The bulk dispersed ZrO₂ nano-laminae could be observed in situ from scanning electron microscopy (SEM) images. The results of X-ray diffraction (XRD) showed that the crystallographic phase of ZrO₂ nano-laminae was cubic ZrO₂. Experiments indicated that the morphologies and phase composition of ZrO₂ nano-laminae were affected by the calcined temperature. PVP plays an important role in the formation process of dispersed ZrO₂ nano-laminae.     

Reactions between La1−x CaxMnO3 and CaO-stabilized ZrO2 part I Powder mixtures

The chemistry and microstructure of the interface between calcium substituted lanthanum manganite and cubic calcia stabilized zirconia have been studied. The aim was to investigate the chemical stability of these materials as a model system for, respectively, the cathode and the electrolyte in solid oxide fuel cells. The relative amounts and time dependence of the formation of secondary phases (La₂Zr₂O₇ and CaZrO₃) and inter-diffusion between the primary phases were observed to depend on temperature, partial pressure of oxygen, and composition of the manganite. 30 mole % Ca on La-site and A-site deficiency of the manganite were shown to stabilize the heterophase interface in air. Reducing conditions were shown to destabilize the primary phases and increase the rate of formation of secondary phases. Pore-coarsening with increasing amount of Ca in the manganite was the most striking feature in the time dependence of the microstructure. The present findings are discussed in relation to the thermodynamic and kinetic stability of the cathode/electrolyte interface of conventional solid oxide fuel cells consisting of yttria stabilized zirconia and strontium substituted lanthanum manganite.     

ZrO2及ZrO2:CdS薄膜的制备和表征

利用ｓｏｌ－ｇｅｌ方法合成了ＺｒＯ_２薄膜,并通过在ＺｒＯ_２薄膜中复合ＣｄＳ纳米粒子成功地制备了ＺｒＯ_２：ＣｄＳ薄膜．制得的ＺｒＯ_２薄膜透明并具有较好的光透射性,而ＺｒＯ_２的含量及膜厚是影响其光透射性的主要因素．分散在ＺｒＯ_２：ＣｄＳ薄膜中的ＣｄＳ纳米粒子为六方相结构,并具有较好的分散性,其平均尺寸为４～６ｎｍ．实验结果表明：ＺｒＯ_２颗粒的晶化会对薄膜的光学性能及表面形貌产生影响,但ＣｄＳ的形成可以抑制薄膜表面ＺｒＯ_２颗粒的晶化,从而得到较为平滑的薄膜．     

ZrO2和ZrO2:Dy3+纳米晶发光特性

采用液相沉淀法制备了不同掺杂浓度和尺寸的ZrO2和ZrO2:Dy纳米晶,研究了其发光特性.结果表明在纳米ZrO₂中,存在着宽带激发和发射,起源为电子在价带和导带之间的跃迁.在Dy³⁺掺杂的样品中,随着颗粒尺寸的长大,其发光增强.并且共掺杂Li⁺的样品发光强度被极大地提高.随着Dy³⁺浓度的变化,黄发射和蓝发射的强度比(Y/B)发生改变,且浓度猝灭是通过近邻激活剂间的交换作用进行的.     

Formation and hot isostatic pressing of ZrO2 solid solution in the system ZrO2-Al2O3

In the system of ZrO₂-Al₂O₃, cubic ZrO₂ solid solutions containing up to 40 mol% Al₂O₃ crystallize at low temperatures from amorphous materials prepared by the simultaneous hydrolysis of zirconium and aluminium alkoxides. At higher temperatures, they transform into tetragonal solid solutions. Metastable ZrO₂ solid solution powders containing 25 mol% Al₂O₃ have been sintered at 1000–1150 °C under 196 M Pausing the hot isostatic pressing technique. The solid solution ceramics consisting of homogeneous microstructure with an average grain size of 50 nm exhibited a very high fracture toughness of 23 MN m ^–1.5. They have been characterized by X-ray diffraction and electron probe surface analyses.     

Low temperature phase equilibria and ordering in the ZrO2-rich region of the system ZrO2-CaO

From co-precipitated powder samples, the solid state reactions occurring between room temperature and 1500° C in the ZrO₂-CaO system have been studied. At low temperatures, compositions containing < 25 mol% CaO show a complex picture of phase transformation and ordering in the system. From the obtained results the following singular reactions have been established. (i) Tetragonal zirconia solid solution decomposes eutectoidally at 7 mol% CaO and 1048 ± 4° C into monoclinic zirconia solid solution and calcium zirconate (CZ). (ii) Cubic zirconia solid solution undergoes a eutectoidal decomposition at 17.5 mol% Cao and 1080 ±20° C into tetragonal solid solution + calcium zirconate. (iii) The monoclinic ordered phase, CaZr₄O₉ (₁), ), undergoes an order-disorder transformation into cubic zirconia solid solution at 1232 ± 5° C. (iv) Cubic zirconia solid solution undergoes a eutectoidal decomposition into two ordered phases, ₁ + ₂ at 21 mol% CaO and 1200 ± 10°C. (v) Hexagonal ordered phase Ca₆Zr₁₉O₄₄ (₂) decomposes peritectoidally into cubic zirconia solid solution + calcium zirconate at 1360 ± 10° C. The two ordered phases ₁ and ₂ seem to be unstable below 1100° C. By using DTA, X-ray diffraction and SEM techniques, the extent of the tetragonal and cubic zirconia solid solution fields have been established. From the above experimental results a new tentative phase diagram is given for the ZrO₂-rich region of the system, ZrO₂-CaO.     

Preparation of ZrO2 and ZrO2-Y2O3 coatings on silicon carbide fibers

The formation of ZrO₂ and ZrO₂-Y₂O₃ coatings from hydrous metal oxide sols on Nicalon NLM 202 silicon carbide fibers is investigated in detail. The results indicate that the microstructure of the oxide layer and the surface morphology of the coatings depend on the physicohemical properties of the sol. Kinetic studies of the oxidation of uncoated and coated fibers at different Y₂O₃ contents demonstrate that the oxidation rate of silicon carbide fibers decreases with increasing coating thickness. The effect of oxidation on the phase composition of Nicalon cloth samples coated with ZrO₂ and ZrO₂-Y₂O₃ is examined.     

Electrical Properties of Sputter-deposited ZrO2-based Pt/ZrO2/Si Capacitors

Pt/ZrO2/Si sandwich structures where ZrO2 is deposited by radio frequency （r.f.） magnetron sputtering using a Zr target in an atmosphere of O2/Ar gas mixture, were fabricated and the effects of the O2/Ar flow ratio in the reactive sputtering process, the annealing temperature, the ZrO2 film thickness on the structure, the surface roughness of ZrO2 films and the electric properties of Pt/ZrO2/Si metal-oxide-semiconductor （MOS） capacitors were investigated. The optimum process parameters of the Pt/ZrO2/Si capacitor based on reactively sputtered-ZrO2 determined in such a way as the capacitance is maximized and the leakage current, the oxide charge, and the interface trap density are minimized that is the O2/Ar flow ratio of 1.5, the annealing temperature of 800℃, and the film thickness of 10 nm. Also the conduction mechanism in the Pt/ZrO2/Si capacitor has been discussed.     

Subsolidus phase relationships in the ZrO2-rich part of the ZrO2–Zr3N4 system

Zirconia can be stabilized by incorporation of nitrogen. The phase relationships in the ZrO2-rich part of the system ZrO2–Zr3N4 have been investigated using high-temperature X-ray methods. At temperatures above 1000°C, a tetragonal and a cubic phase with randomly distributed vacancies exists, depending on the amount of incorporated nitrogen. This high-temperature behaviour is similar to that of systems like ZrO2–Y2O3, which is another indication for the important role of anion vacancies in zirconia systems. Below 1000°C, β-type phases with an ordered arrangement of anion vacancies are stable. This revised version was published online in November 2006 with corrections to the Cover Date.     

PET接枝改性纳米ZrO2/PC复合材料的力学性能

采用接枝聚合反应在纳米ZrO₂表面接枝聚对苯二甲酸乙二醇酯 (PET) 低聚物,以提高其与聚碳酸酯(PC)的相容性;改性纳米ZrO₂与PC经过共混挤出,制备了纳米ZrO₂/PC复合材料。采用FTIR、XPS、TEM、TG、接触角等测试方法对接枝改性后的纳米ZrO₂进行了表征,结果表明,PET化学键合到了纳米ZrO₂表面,使ZrO₂疏水性显著增强,微观颗粒分散性好。对纳米ZrO₂/PC复合材料进行了力学性能测试,探讨了纳米ZrO₂的添加量与复合材料力学性能的关系。结果表明：纳米ZrO₂/PC复合材料的力学性能较纯PC有明显改善;随着改性纳米ZrO₂含量的增加,缺口冲击强度和拉伸强度都呈现出先增加后降低的趋势,分别在ZrO₂质量分数为1%和0.3%时达到最大值;弯曲强度在实验范围内一直呈上升趋势,最大弯曲强度比纯PC提高2.54 MPa。     

Superplasticity of ZrO2 and ZrO2/Al2O3 composite consisting of nano-sized grains

 Y₂O₃-stabilized ZrO₂ and Y₂O₃-stabilized ZrO₂/10 mol%Al₂O₃ composite both consisting of homogeneous nano-sized grains were successfully fabricated by a pulse electric current sintering through solution chemistry technique. The relative density was above 97% for both the obtained materials, and the grain size was less than 90 nm and 40 nm for the ZrO₂ monolith and the ZrO₂/Al₂O₃ composite, respectively. The materials showed superplastic behavior in compression at temperature of 1200°C. Received: 2 March 1998 / Accepted: 10 March 1998     

Crystal growth of tetragonal ZrO2 in the glass system ZrO2-SiO2 prepared by the sol-gel process from metal alkoxides

Glasses in the system ZrO₂-SiO₂ containing 40 to 60 mol % ZrO₂ were prepared by the sol-gel process from metal alkoxides. Tetragonal ZrO₂ was precipitated by heat treatment at 800 and 1200° C, and its crystal growth was measured by differential thermal and X-ray diffraction analyses. At 800 to 900° C, tetragonal ZrO₂ crystals grew three-dimensionally and the activation energy for growth was calculated as about 680 kJ mol⁻¹. On the other hand, the secondary growth of tetragonal ZrO₂ at 1000 to 1200° C followed the cube-root-of-time law. The activation energy for secondary growth was about 380 kJ mol⁻¹. It is suggested that the diffusion of Zr⁴⁺ ions is the rate-limiting process for the secondary crystal growth of tetragonal ZrO₂.