Al2O3含量对Al2O3/LiTaO3复合陶瓷介电性能的影响

采用热压烧结法制备了Al₂O₃/LiTaO₃ (ALT) 陶瓷复合材料, 研究了Al₂O₃不同体积含量(5vol%、10vol%、15vol%和20vol%)对LiTaO3压电陶瓷介电性能的影响. 结果表明：随着频率的增加, 不同Al₂O₃含量的ALT陶瓷复合材料的介电常数和介电损耗均降低, 但降低的幅度不同. 少量Al₂O₃(5vol%)的添加既能增大材料的介电常数同时又降低了材料的介电损耗, 但是随着Al₂O₃含量的继续增加, ALT陶瓷复合材料的介电常数和介电损耗都增大, 其居里温度先升高后降低. Al₂O₃作为第二相不但能促进LiTaO3陶瓷烧结致密,而且对ALT陶瓷复合材料的介电性能也有提高.     

温梯法蓝宝石(Al2O3)晶体的脱碳去色退火研究

温度梯度法(TGT)生长的Al2O3晶体因石墨发热体在高温时的挥发和原料中过渡性金属离子的存在,晶体在不同部位呈现不同颜色,一般上部为浅红色,尾部为浅黄绿色.将TGT法生长的Al2O3晶体(φ110×80mm3)依次经过高温氧化气氛、高温还原气氛脱碳、去色退火实验,即"两步法"退火实验,晶体变成无色、透明.经测试,Al2O3晶体的完整性、光学透过率和光学均匀性均有显著提高.     

ZrO2对NiO/CeO2/γ-Al2O3复合催化剂结构的影响

以Ni(NO₃)_2·6H₂O、Al(NO₃)₃·9H₂O、ZrOCl_2·8H₂O和Ce(NO₃)_3·6H₂O为原料,采用共沉淀法分别制备了NiO/CeO₂/γ-Al₂O₃和NiO/CeO₂-ZrO₂/Al₂O₃催化剂.通过X射线衍射（XRD）、透射电子显微镜（TEM）和近边X射线吸收精细结构（XANES）等方法对催化剂的组成结构进行表征.结果表明,煅烧温度高于600℃时,NiO/CeO₂/γ-Al₂O₃催化剂中的NiO与γ-Al₂O₃载体发生作用,形成NiAl₂O₄尖晶石;而NiO/CeO₂-ZrO₂/Al₂O₃催化剂中,NiO能够稳定存在,没有NiAl₂O₄尖晶石生成,且Al₂O₃与CeO₂和ZrO₂作用形成一种新的Zr_0.30Ce_0.45Al_0.25O_1.87固溶体.     

水热法生长复合钛宝石激光晶体

水热法生长了复合钛宝石(Al₂O₃/Ti:Al₂O₃)激光晶体.对外层Al₂O₃X射线ω扫描表明其晶体质量很高.外层生长的Al₂O₃和内部的钛宝石激光棒结合牢固、紧密,因而能适应高强度泵浦所带来的激光介质内部的热应力.复合激光晶体界面层带来的光损耗很小.就我们所知,这是首次用水热法生长复合激光晶体.     

纳米α-Al2O3/W复合粉体的制备

论述了非均相沉淀法制备纳米α—Al₂O₃/W复合粉体的实验过程,以及纳米钨粉对α—Al₂O₃相转变温度的影响.结果表明:纳米钨粉的存在降低了α—Al₂O₃的相转变温度.本实验所制凝胶在1000℃真空中煅烧1h可获得平均粒径<50nm的α—Al₂O₃/W粉体.     

硅衬底Al2O3∶Tb3+薄膜的制备及其发光性能

采用溶胶凝胶法在硅衬底上制备了Al₂O₃∶Tb³⁺薄膜; 并采用DTA-TG、XRD、SEM、AFM及光致发光光谱对其进行了一系列表征; 分析了Al₂O₃∶Tb³⁺薄膜的发光机理, 探讨了热处理温度和Tb³⁺掺杂浓度对发光性能的影响规律. 研究结果表明, 采用溶胶凝胶法制备工艺, 制备了高发光强度的Al₂O₃∶Tb³⁺薄膜, 薄膜的最佳激发波长为240nm, Tb³⁺的最佳掺杂浓度为5mol%(Tb₂O₃/Al₂O₃=5mol%), 在240nm光激发下, 最强的发射峰出现在544nm附近; 并且制备的Al₂O₃∶Tb³⁺薄膜表面致密、平整且无裂纹产生, 表面粗糙度约为1.3nm, 有利于硅基光电子器件的制备和应用.     

燃烧条件对自蔓延高温合成Al2O3/AlB12复相陶瓷粉体特性的影响

以铝、B₂O₃为原料,利用自蔓延高温合成（SHS）制备了Al₂O₃／AlB₁₂复相陶瓷粉体,研究了燃烧条件对粉体特性的影响．结果发现,经球磨处理后,复相陶瓷粉体中Al₂O₃的平均粒径为3～4μm,AlB₁₂的粒度为亚微米级．粉体的比表面积为～1m²／g．燃烧过程中B₂O₃易于挥发,并在合成产物的表层生成B₂O₃和9Al₂O₃·2B₂O₃副产物相．在较低压力的氩气中进行合成,可以减少副产物相,获得纯度较高的复相陶瓷．与实际测量的燃烧温度对比发现,按照化学反应式13Al＋6B₂O₃＝6Al₂O₃＋AlB₁₂,通过热力学计算得到的绝热燃烧温度明显偏高．     

退火温度对Pt/SrBi2Ta2O9/Bi4Ti3O12/p-Si异质结微观结构与性能的影响

采用sol-gel工艺制备了Pt/SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂/p-Si异质结. 研究了退火温度对异质结微观结构与生长行为、漏电流密度和C-V特性等的影响. 研究表明: 成膜温度较低时,SrBi₂Ta₂O₉、Bi₄Ti₃O₁₂均为多晶薄膜, 但随退火温度升高, Bi₄Ti₃O₁₂薄膜沿c轴择优生长的趋势增强; 经不同退火温度处理的Pt/SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂/p-Si异质结的C-V曲线均呈现顺时针非对称回滞特性, 且回滞窗口随退火温度升高而增大, 经700℃退火处理后异质结的最大回滞窗口达0.78V; 在550～700℃范围内, Pt/SrBi₂Ta₂O₉/Bi₄Ti₃O₁₂/\\p-Si异质结的漏电流密度先是随退火温度升高缓慢下降, 当退火温度超过650℃后漏电流密度明显增大, 经650℃退火处理的异质结的漏电流密度可达2.54×10^-7A/cm²的最低值.     

Al2O3-SiO2复合膜的制备与结构表征

以异丙醇铝和正硅酸乙酯为主要原料,用溶胶-凝胶法制备无支撑体Al₂O₃-SiO₂复合膜.应用XRD、DTA-TGA、IR、BET等测试手段对复合膜的物相组成、热稳定性、孔结构进行表征.并且讨论了化学组成和煅烧温度对复合膜孔结构的影响.研究结果表明:550℃煅烧10h的复合膜物相组成为无定形的SiO₂和γ-Al₂O₃晶体,粒度大小在2-4nm之间,化学组成为Al₂O₃/SiO₂=3:2的复合膜在不同煅烧温度时,400℃煅烧的物相为γ-AlOOH和,γ-Al₂O₃,550-1150℃煅烧的物相为γ-Al₂O₃,1220℃煅烧的物相为γ-Al₂O₃和α-Al₂O₃,1300℃煅烧的物相为莫来石相和α-Al₂O₃;化学组成不同的复合膜主要是由Al-O网络和Si-O网络构成,没有形成Al-O-Si网络结构;复合膜具有良好的热稳定性;化学组成和煅烧温度对复合膜的孔结构有一定的影响.     

碳酸盐共沉淀法解决GGG单晶生长过程中的挥发问题

用碳酸盐作沉淀剂,采用无机体系共沉淀法制备了钆镓石榴石Gd₃Ga₅O₁₂(GGG)前驱体.由TG-DTA和IR光谱分析表明,合成的沉淀为碱式碳酸盐,煅烧过程中失重为28.06％.XRD分析表明在1000℃煅烧3h可以得到晶化完全的GGG多晶料,通过与固相反应比较可知,碳酸盐共沉淀法制备GGG多晶料具有反应时间短、晶化程度高、煅烧温度低、Ga₂O₃挥发量少等优点.GGG晶体提拉生长表明,Gd₂O₃和Ga₂O₃的组分失配问题已经得到基本解决,从而大大提高了单晶的光学质量.     

蓝宝石光纤高温测量技术进展

温度是表征物体状态的参数之一,在科学研究和工程应用中具有重要的理论意义和价值。在氧化、高温、腐蚀、电磁干扰等恶劣环境下,温度的准确测量一直是难题。传感器材料是进行温度测量的基础。蓝宝石单晶光纤具有物理化学性能稳定、熔点高、机械性能强等优点,是进行高温测试的一种首选材料。本文介绍了利用蓝宝石单晶光纤进行温度测量的几种方法,即蓝宝石光纤辐射高温测试技术、蓝宝石光纤光栅高温测试技术、蓝宝石光纤珐珀高温测试技术、蓝宝石超声波导高温测试技术的原理、现状、优缺点及发展趋势,并进行了比较,为蓝宝石光纤温度测量应用奠定基础。     

Growth of bismuth sulpho-iodide single crystals from vapour

Bismuth sulpho-iodide single crystals were grown from the vapour phase for various temperature gradients. When the temperature gradient was kept at 2° C cm^–1 in a horizontal furnace a large polycrystalline boule was obtained. The boule consisted of thick platelets at the top and needles at the bottom. When the temperature gradient was decreased to 1° C cm^–1 very good needles of length 2 cm and thickness varying from 0.5 to 2 mm were obtained. They grew as hollow needles in a vertical furnace. The grown crystals were of length 1.5 cm and thickness ranging from 0.5 to 1 mm.     

Interface transitions in Czochralski growth of garnets

A source of variation in boule diameter, that has not been previously described, has been observed to occur during automated or weight regulated pulling of garnets from the melt. The effects are related to refractive index variations observed in longitudinal cross section under polarized light. Solution at the tip of boule simultaneously with compensatory lateral growth higher on the crystal melt interface can take place under low temperature gradient conditions. This occurs when heat flow or radiation loss through the crystal is insufficient to preserve the initial, faceted or approximately conical, interface shape.     

蓝宝石强化研究进展

蓝宝石窗罩在气动热效应作用下易产生破裂,使其结构/功能失效.提高蓝宝石高温强度可有效抑制其高温断裂行为.结合国内外研究成果,从蓝宝石高温失效机理、蓝宝石高温强度表征新方法和蓝宝石强化方法等方面,综合评述了蓝宝石强化研究领域的最新成果,其中重点介绍了蓝宝石强化的研究进展,最后指出了我国蓝宝石强化研究的努力方向.     

影响蓝宝石高温强度的因素探讨

蓝宝石优秀的光学和力学性能使得它在红外光学领域获得广泛应用,但是,其高温强度的急剧降低,限制了它的热震抗力的发挥.所以改善蓝宝石的高温强度已经成为目前该领域的研究热点之一.本文介绍蓝宝石高温强度降低的机制以及影响因素,并对未来的工作提出展望.     

Preparation, quality characterization, service performance evaluation and its modification of sapphire crystal for optical window and dome application

Sapphire (i.e., Al₂O₃ single crystal) window and dome are important sensor components. Large-sized sapphire crystal was prepared by an improved Kyropoulos method, and its machining technique of ultrasonic vibration was also reported. The quality and structure were evaluated by illumination of a He–Ne laser transmission electron microscopy (TEM), double crystal X-ray diffraction (DCXRD) and Raman spectroscopy. For practical window and dome application, its high-temperature mechanical strength and optical transmission were both measured, and a modification measure of sputtering Mg film on sapphire surface followed by annealing and subsequent quenching was demonstrated. Large-sized sapphire crystals with high quality and different profiles were successfully grown by adjustment of pulling velocity and crucible size, design of suitable temperature field. Moreover, a series of sapphire windows and domes were fabricated for different optical application. The biaxial flexure strength of sapphire crystal decreases with increasing temperature, and the infrared transmission is also slightly degraded at high temperature. In addition, it should be noted that there is sharp strength drop in the temperature range of 400° to 600 °C which is related with twin formation in sapphire crystal. Submicron MgAl₂O₄ spinel precipitation can effectively harden sapphire crystal and do not induce large optical-scattering loss, which is a potential modification method for window and dome application of sapphire crystal.     

Bulk Microwave Conductivity of Semiconductors Determined from TEo01-Mode Reflectivity of Boule Surface

This paper describes an "electrodeless" technique for measuring microwave conductivity and dielectric constant of a bulk semiconductor boule without the necessity of fabricating samples. All that is required is that the boule be sufficiently large and that it have one planar surface. The planar surface is butted up to a flange terminating a circular waveguide. The complex TEo01 (circular E-field) mode-reflection coefficient at the surface is then measured with a reflection-coefficient bridge. Because of the particular properties of this mode, no contact impedance occurs as does in the case of the TE10? mode. Thus the measurements yield the true bulk properties of the material. To demonstrate the technique, 48- and 72-GHz measurements of the conductivity and permittivity of a number of semiconductor boules at room temperature are presented and are shown to agree favorably with results obtained by other means.     

提高蓝宝石高温强度的研究进展

提高蓝宝石高温强度的研究已成为蓝宝石在高速、高温应用中一个亟待解决的重要课题.简要介绍了蓝宝石的高温失效及几种正在研究与发展的改善方法,并提出了今后需要进一步研究的关键问题.     

A method to synthesize SiO2–TiO2 glasses based on the synergy between VAD and ALD techniques: study of TiO2doping profile along radial direction

This study aimed the synthesis of titania–doped silica glasses with controlled TiO₂ concentrations and distribution profiles through the synergy between Vapor-Phase Axial Deposition (VAD) and Atomic Layer Deposition (ALD) techniques. In a first stage, porous boules of pure silica were synthesized by the VAD technique. Afterwards, these boules were submitted to a cyclic doping process with TiCl₄ vapor and H₂O vapor using the principles of ALD technique. Silica–titania on glassy state was obtained after the consolidation of the porous boule at 1400 °C. The effects of VAD and ALD parameters were studied on the radial doping profile homogeneity and glass structure in the consolidated material. Concerning to the radial profile, a more homogeneous glass was obtained for porous boules doped at 90 °C and with higher average density. This temperature was enough to suppress the effect of TiCl₄ condensation on the porous boule surface even for a long TiCl₄ flow time, providing a relatively high doping homogeneity for one and four ALD cycles. The opacity in some consolidated samples was attributed to a segregated phase, which could be completely eliminated by a second heat treatment in flame.     

蓝宝石单晶光纤高温传感头的高温损伤机制

揭示了蓝宝石单晶光纤高温传感头在高温下的性能劣变现象,指出光纤表面在高温下的永久损伤是产生性能劣变的主要原因。通过对光纤表面的显微分析,明确了损伤的主要机制为外部杂质在高温下与光纤表面的相互作用。并由此确认特殊的光纤表面保护可以保证蓝宝石单晶光纤高温传感头在高温下的稳定工作。