不添加烧结助剂制备透明的Y2O3陶瓷

以Y2O3粗粉、碳酸氢铵、硝酸和氨水为原料,通过沉淀法制备了Y2O3纳米粉体.发现沉淀工艺和煅烧温度显著影响Y2O3纳米粉的颗粒大小和尺寸分布,从而影响烧结体的密度和透光性.用X射线衍射分析仪、透射电镜、图像分析仪等研究发现,pH=8时制得的沉淀先驱物经1000℃煅烧,可得到粒度为33 nm,近球形,分散性好,尺寸分布窄的Y2O3粉体.该粉体不加任何添加剂,在1700℃真空烧结4 h可得到透明Y2O3陶瓷.     

Al2O3透明陶瓷显微结构的研究

采用高纯Al2O3(＞99.9%)粉末为原料,用无压烧结工艺制备Al2O3透明陶瓷.研究了添加剂Y2O3、烧结温度、保温时间等对Al2O3透明陶瓷显微结构和光学性能的影响.实验结果表明,适量的Y2O3能够抑制Al2O3晶粒的生长,改善烧结性能,但添加量过多会使Al2O3陶瓷气孔略有增加.在1800℃烧结的样品密度接近理论密度,具有较好的光学性能.延长保温时间能够使晶粒长大的同时有效排除晶界处少量气孔.     

Y2O3掺杂量对ZnO-Bi2O3-Nb2O5压敏陶瓷电性能的影响

通过掺杂Y2O3和优化烧结工艺制备了ZnO-Bi2O3-Nb2O5压敏陶瓷。利用XRD、SEM和VSR研究了Y2O3掺杂量对其电性能的影响。结果表明，随着Y2O3掺杂量增加，陶瓷电阻率ρ减小，非线性系数α增大；Bi2O3气氛下烧结（1170℃、保温2．5h）的陶瓷，当x（Bi2O3）和x（Nb2O5）为3％、y（Y2O...     

B2O3-Al2O3-SiO2透明玻璃陶瓷研究

玻璃陶瓷属于一类多晶陶瓷材料.通过调整玻璃基质和晶相组成可以制备出具有良好的力学、热学、电学和光学性能的玻璃陶瓷材料.采用传统的熔融和退火技术制备出含B2O3-Al2O3-SiO2-Li2O-K2O组分的硼铝硅玻璃,并通过成核和长晶工艺最终制备出透明玻璃陶瓷.配合料在铂金坩埚中于1450℃下熔融2h,然后经两步热处理制度控制晶核的生成和晶粒的长大.采用差热分析技术确定成核和长晶温度.采用X射线衍射技术对不同热处理制度下的玻璃陶瓷样品进行分析,以确定最佳成核和长晶条件.采用扫描电子显微镜分析玻璃陶瓷形态,晶粒尺寸及其在残余玻璃相中的分布.采用UV-Vis-Nir分光光度计测定玻璃陶瓷样品的透过率.     

共沉淀法制备Nd3+:Y2O3透明陶瓷

以Y2O3为基质材料,掺杂不同含量的Nd3+添加PEG和(NH4)2SO4为分散剂,采用共沉淀法制备出性能良好的Nd3+:Y2O3纳米粉.对前驱体和不同温度下煅烧后的粉体进行差热热重、X射线衍射、比表面积和透射电镜等分析.结果表明,前驱体产物为Y2(OH)5(NO3)·nH2O时,Nd3+完全固溶于Y2O3的立方晶格中,Nd3+:Y2O3粉体大小均匀,近似球形.随着煅烧温度的升高,颗粒逐渐长大,900℃煅烧2h后颗粒尺寸约为40～60nm;粉体在1700℃和真空度为1×10-3Pa条件下烧结6h得到的Nd3+:Y2O3透明陶瓷的透光率接近78%.     

钕离子掺杂钇铝石榴石(Nd3+:Y3Al5O12)透明陶瓷研究进展

回顾了新一代激光工作物质Nd3+:Y3Al5O12透明陶瓷的发展历史,并与激光晶体进行了比较,介绍了其技术优势,同时简述了Nd3+:Y3Al5O12透明陶瓷的2种常用工艺.     

Y2O3和B2O3对莫来石低温烧结的影响

由于Si4+和Al3+离子在莫来石晶界处扩散速率低,莫来石陶瓷难以烧结.为了降低莫来石陶瓷的烧结温度,在莫来石中添加Y203.B2O3为烧结助剂,研究了添加剂在单独和混合添加情况下对莫来石陶瓷体积密度、抗弯强度以及微观形貌等的影响.同时,研究了烧结温度及保温时间对莫来石陶瓷性能的影响.研究表明,添加剂显著地降低了莫来石的烧成温度,添加Y2O3充当烧结助剂比添加B2O3具有更好的效果,随着温度的提高,陶瓷强度由37.39MPa增至77.89MPa,体积密度由1.99g/cm3增至2.60g/cm3.     

超重力下燃烧合成Al2O3-ZrO2(Y2O3)共晶陶瓷组织性能演化

采用超重力下燃烧合成工艺进行Al2O3-ZrO2 (4Y)共品陶瓷的制备,研究了Al2O3-ZrO2(4Y)共晶陶瓷的凝固行为、组织演化与力学性能的关系.XRD、SEM与EDS分析显示陶瓷基体组织是由表层的微纳米晶组织和心部的ZrO2四方相微米球品组织组成.陶瓷表层微纳米品组织的形成是因Al2O3高熵相率先形核和Al2O3各向异性生长,诱发Al2O3-ZrO2(4Y)小平面-小平面共晶生长所致;处于陶瓷心部的ZrO2四方相微米球晶组织则是因ZrO2高温立方相快速生长,导致Al2O3和ZrO2独立长大所致.力学性能测试结果表明因陶瓷凝固行为引起的显微组织演化,使其表层具有最大的维氏硬度(20.2GPa),而其心部则具有最高的断裂韧性(18.5±1.6MPa·m1/2),陶瓷弯曲强度达至1268±112MPa.     

MgO-Al2O3-SiO2-TiO2-Y2O3玻璃的弹性模量

根据硬盘基板用材料的要求,制备了MgO-A12Oa-SiO2-TiO2-Y2Oa高弹性模量玻璃(120GPa).玻璃的弹性模量随组成的变化服从Makishima-Mackenzie理论,MgO、A12O3、TiO2、Y2O3等具有较高单位体积离解能的氧化物有利于提高玻璃的弹性模量.但玻璃弹性模量的理论计算值低于测试值.这是因为Makishima-Mackenzie理论没有考虑玻璃内阳离子的具体配位状态,对MgO、Y2O3堆积密度因子的推导存在误差.因此利用Makishima-Mackenzie理论发展高弹性模量玻璃时应对MgO、Y2O3等氧化物的计算进行修正.     

Y3+取代Bi3+的Bi2O3-ZnO-Nb2O5基陶瓷的结构与介电性

研究了Y3 取代的Bi2O3-ZnO-Nb2O5(BZN)基陶瓷(Bi1.5-xYxZn0.5)(Zn0.5Nb1.5)O7(0≤x≤1.5,BYZN)的结构和介电性能.采用传统的固相反应法制备陶瓷样品,XRD分析样品的相结构,SEM分析样品的微观形貌.结果表明:BZN陶瓷的结构为立方焦绿石单相;当Y3 取代量较少(0＜x≤0.3)时,样品的相结构仍然保持立方焦绿石单相;随着Y3 取代量的进一步增加(x≥0.6),样品由立方焦绿石相向YNbO4和ZnO复相过渡.同时,样品的介电性能随结构的变化而呈现有规律的变化.     

Electroluminescence of Y2O3:Eu and Y2O3:Sm films

Electroluminescence of Y₂O₃:Eu and Y₂O₃:Sm films, as well as the films coactivated with Eu and Sm, is studied. The electroluminescence spectra are measured. The physical mechanism of electroluminescence is analyzed It is shown that the increase in the heat treatment temperature and the content of doping impurities of the films enhances the intensity of electroluminescence. Additional doping of Y₂O₃:EuF₃ films by the SmF₃ impurity, practically does not influence the emission spectrum.     

Synthesis and characterization of rod-like Y2O3 and Y2O3:Eu3+

Y₂O₃ rods 100 to 200 nm in diameter and 10 to 20 m in length are accessible via polyol-mediated synthesis of a precursor material with similar shape. By heating of Y(CH₃COO)₃ · xH₂O and a defined amount of water at 190°C in diethylene glycol, the rod-like precursor material is formed. Infrared spectroscopy (IR), differential thermal analysis (DTA) and thermal gravimetry (TG) evidence that this precursor material still contains acetate. However, the precursor material can be transformed to Y₂O₃ by sintering at 600°C without destruction of the rod-like shape. According to X-ray powder diffraction analysis, the rods are well crystallized. They can be assumed to be with [100] orientation. By doping with Eu³⁺ (5 mol%), red emitting phosphor rods can be realized. With optical spectroscopy the typical line emission of Eu³⁺ is observed. Diffuse reflectance of Y₂O₃:Eu³⁺ rods is determined to be higher than 95% in the visible. While exciting at 254 nm (Hg-discharge), a quantum efficiency of 38.5% is proven for the prepared Y₂O₃:Eu³⁺ rods.     

Plasma spraying of Al2O3 and Al2O3Y2O3

A microstructural study has been carried out of plasma-sprayed Al₂O₃ and mixed and sintered Al₂O₃Y₂O₃. In order to ascertain the degree of metastability achieved by plasma spraying, these results are compared with a similar experiment utilizing a CO₂ laser for melting and the hammer-and-anvil technique for quenching of the same materials. X-ray diffraction methods were used to determine the obtained phases and crystal structures. In addition, transmission electron microscopy was used to confirm the phases present and to study their morpology. The porosity was studied with both mercury intrusion porosimetry and small angle neutron scattering. The addition of Y₂O₃ is shown to decrease the porosity from 15% to 7.5%. Adhesion is likewise related to the addition of Y₂O₃ and it is seen that adhesion of the mixture is measurably improved over that of pure Al₂O₃. The implication of these results is discussed.     

纳米Y_2O_3:Eu~(3+)(Y_2O_3)粉体的红外光谱研究

采用均相沉淀法和燃烧合成法制备了不同粒径的粉体材料Y2O3:Eu3+,着重研究了样品的红外光谱,探讨了纳米晶Y2O3:Eu3+与同质微米材料相比的微观结构的变化.研究发现,波数位于563 cm-1的Y(Eu)—O键的吸收峰校正高度和面积对于纳米级粒径的粉体材料随着颗粒的减小而减小,而对于同质微米材料却相反.经分析认为:Y(Eu)—O键的吸收峰校正高度和面积由Y(Eu)—O键的平均键长和Y(Eu)—O键振动态数目这两个因素决定.对于微米粉体Y(Eu)—O键长的变化起主要作用,而对于纳米粉体由于不饱和键和悬空键的形成,Y(Eu)—O键振动态数目的变化起主要作用.     

Infrared Luminescence of Y2O2S:Er3+ and Y2O3:Er3+

The diffuse reflectance and luminescence spectra of Y₂O₂S:Er³⁺ and Y₂O₃:Er³⁺ are studied under selective and polarized laser excitation. The results indicate that the Er³⁺ luminescence bands of yttrium oxysulfide in the 1.54-m region are one order of magnitude stronger and broader than those of yttria. Y₂O₂S:Er³⁺ is shown to contain two types of Er-related emission centers differing in the anion environment of the Er³⁺ ion.     

Electrical conductivity of Cr2O3-doped Y2O3-stabilized ZrO2

The electrical conductivity of Cr₂O₃-doped Y₂O₃-stabilized ZrO₂ (YSZ) has been studied as functions of composition, temperature and oxygen pressure. The specimens have been prepared by hot preoning of co precipitated oxides to yield >99.7% density. The Cr₂O₃ added above the solubility limit ( 0.7 mol %) precipitated as a secondary phase at the grain boundaries. The conductivity of Cr₂O₃-doped YSZ was almost independent of the oxygen pressure in the range 10¹⁸ to 10⁵ Pa, indicating a dominant ionic condition. The electronic conductivity of dopant CR₂O₃ would be hindered by the higher ionic conductivity in thep _O2 ranges studied. The conductivity and the activation energy for conduction decreased slightly with the addition of Cr₂O₃. These phenomena seemed to be caused by vacancy trapping or polarization at the grain boundaries with the Cr₂O₃ precipitates. The samples with 1 mol % Cr₂O₃ addred to zirconia containing various Y₂O₃ contents showed similar conduction behaviour to those without Cr₂O₃ addition; that is, the conductivity maxima are observed at around 8 mol % Y₂O₃ addition to zirconia, and the activation energies increased with tha Y₂O₃ addition.     

Analytical transmission electron microscopy of La2O3-doped Y2O3

Analytical electron microscopy has been used to study the precipitation reactions in sintered samples of 9 mol% La₂O₃-Y₂O₃ samples upquenched from the single phase cubic region into the cubic and hexagonal phase field. Samples annealed just inside the two-phase cubic-cubic and hexagonal solvus exhibited predominantly grain boundary precipitation. Small La₂O₃ rich second phases formed within the first ten minutes and developed into strained, facetted precipitates after 300 min. Intergranular and intragranular precipitation occurred in samples annealed further into the two-phase field. Strained, lathlike La₂O₃-rich monoclinic precipitates, exhibiting a preferrred orientation in the matrix, appeared as the dominant morphology for long times at temperature. Chemical microanalyses of the strained structures obtained in samples annealed for 300 min revealed La₂O₃ matrix concentrations in agreement with phase diagram predictions. However, the La₂O₃ concentrations in the second-phase precipitates were found to be far in excess of the cubic and hexagonal-hexagonal solvus. This discrepancy is believed to arise from a re-equilibration of the second phase in the cubic and monoclinic phase field during quenching.