Al and Ti secondary neutral and secondary ion emission from oxide samples in the high-frequency sputtering mode of HF-plasma SNMS

A strong Al⁺ and a minor Ti⁺ peak without a proportional increase of the O⁺ signal in SNMS high-frequency sputtering mode (HFM) time profiles of an insulating μm-thick oxide layer on Ti-48Al-2Cr-2Nb led us to check for a possible contribution of positive secondary ions (SI⁺). SI⁺ and SI^– (negative secondary ions) can be detected in ion energy spectra. This is shown using Al⁺, O^–, AlO^–, and AlO₂ ^– ions sputtered from massive Al₂O₃. Similarly, and depending on stoichiometry, also Ti⁺ from mixed sintered, microscopically inhomogeneous Al₂O₃-TiO₂-SiO₂ pellets has been identified to be partly SI⁺. The subtraction of an assumed contribution of ionized secondary neutrals (SN⁺) suggests that SI⁺ may form several 10% of the detected ions obtained in the HFM sputtering and plasma processes. However, the positive surface potential of some 10 V being necessary to cause detectable SI⁺ contributions does not build up on μm-thin insulating layers. Therefore, we have to conclude that the Al⁺ and Ti⁺ peaks in the sputter time profiles of the μm-thick oxide layer on Ti-48Al-2Cr-2Nb which are accompanied by an O⁺ deficiency cannot have been caused by SI⁺. Instead, their more probable origin is the inhomogeneous Al₂O₃ interlayer itself. Together with the residues of a topmost TiO₂ layer which has strongly been depleted in O by preferential sputtering, the relative O⁺ deficiency may be explained without assuming SI⁺ contributions. Received: 22 February 1999 / Revised: 1 July 1999 / Accepted: 6 July 1999     

YAlO3的体色与缺陷平衡的关系

利用固相扩散法在1 450 ℃下制备了YAlO₃粉末样品和陶瓷片样品,并在不同温度和不同气氛(air, O₂ or N₂)下对样品进行退火处理调制了其缺陷浓度.基于漫反射光谱和交流阻抗谱分析了YAlO₃样品的体色与其缺陷浓度之间的关系.研究结果表明YAlO₃具有p型导电机理,其浅棕色体色是由阳离子空位引起的.在高温和氮气氛下处理该材料其缺陷浓度减少,体色变浅.第一性原理计算结果认为YAlO₃中的主要缺陷应该是铝空位V_Al^×.     

致密的5%Al3+掺杂的SnP2O7-SnO2复合陶瓷在中温燃料电池中的应用

首先制备了未掺杂和5%(摩尔分数)Al³⁺掺杂SnO₂的多孔性基片, 然后将基片与85%的H₃PO₄在600℃下反应, 分别得到了致密的未掺杂和5%Al³⁺掺杂的SnP₂O₇-SnO₂复合陶瓷样品. 采用X射线衍射(XRD), 扫描电子显微镜(SEM)和X射线能量色散谱(EDS)测试方法对样品进行了表征, 采用电化学阻抗谱法(EIS)测试了样品在中温(100-250℃)下, 湿润空气和湿润氢气气氛中的电导率. 结果表明, 在湿润空气和湿润氢气中, 5%Al³⁺掺杂的SnP₂O₇-SnO₂复合陶瓷样品的电导率均高于未掺杂的SnP₂O₇-SnO₂复合陶瓷样品的电导率, 且该复合陶瓷样品在湿润空气和湿润氢气中250℃下, 电导率分别达到最大值: 4.30×10^-2和6.25×10^-2 S·cm^-1, 高于至今报道的SnP₂O₇-SnO₂基复合陶瓷及SnP₂O₇基陶瓷在类似条件下的电导率. 以5%Al³⁺掺杂的SnP₂O₇-SnO₂复合陶瓷样品(厚度: 1.45 mm)为电解质, 多孔性铂为电极组装成的氢气/空气燃料电池具有良好的中温电池性能, 175、200、250℃的最大输出功率密度分别为52.0、61.9、82.3 mW·cm^-2. 良好的中温电池性能与该复合陶瓷电解质较高的电导率和致密度及该燃料电池较低的界面极化电阻有关.     

YAlO3的体色与缺陷平衡的关系

利用固相扩散法在1 450 ℃下制备了YAlO₃粉末样品和陶瓷片样品,并在不同温度和不同气氛(air, O₂ or N₂)下对样品进行退火处理调制了其缺陷浓度。基于漫反射光谱和交流阻抗谱分析了YAlO₃样品的体色与其缺陷浓度之间的关系。研究结果表明YAlO₃具有p型导电机理,其浅棕色体色是由阳离子空位引起的。在高温和氮气氛下处理该材料其缺陷浓度减少,体色变浅。第一性原理计算结果认为YAlO₃中的主要缺陷应该是铝空位V_Al^×。     

Li4Ti5O12/(Ag+C)电极材料的固相合成及电化学性能

以Li₂CO₃,TiO₂为原料,葡萄糖为碳源,采用固相煅烧工艺合成了亚微米级的Li₄Ti₅O₁₂/C复合负极材料。并将之与AgNO₃复合,采用固相方法制备出了Ag表面修饰的Li₄Ti₅O₁₂/(Ag+C)复合材料。采用XRD、SEM和TEM测试方法对材料的微结构进行了表征。结果表明,C的存在对Ag单质在Li₄Ti₅O₁₂/C颗粒表面的大量形成起到了积极的促进作用,从而很大程度地提高了Li₄Ti₅O₁₂/C的电导率,因此有效地改善了其电化学性能。在1C倍率下,Li₄Ti₅O₁₂/(Ag+C)复合材料的首次放电容量达到了164 mAh·g^-1。     

固溶体结构对Ca2-xSrxZn4Ti15O36∶Pr3+发光性质的影响

Ca_2-xSr_xZn₄Ti₁₅O₃₆∶Pr red long decay phosphor was synthesized by high temperature solid state reaction. Photoluminescence property and crystalline and unit cell parameters of the orthorhombic were investigated by fluorescence spectrophotometer and by powder X-ray diffraction, respectively. The emission intensity at 618 nm changes sharply when the concentration of Sr²⁺ (x) is less than 0.1 and the emission intensity reaches the maximum when x is equal to 0.007. There is an obviously broad excitation band at 270 nm when x is equal to 0.003 and it disappears gradually when x is over 0.01. The unit cell a parameter of Ca_2-xSr_xZn₄Ti₁₅O₃₆∶Pr decreases while c parameter increases with the increases of the concentration of the doped Sr²⁺. When x is over 0.1 the value of the unit cell parameters a and c become stable. TL peaks of Ca₂Zn₄Ti₁₅O₃₆∶Pr, Ca_1.993Sr_0.007Zn₄Ti₁₅O₃₆∶0.002Pr³⁺, 0.002Na⁺, are located at 62 ℃, 88 ℃, respectively, which indicates that there are deeper traps in Ca_1.993Sr_0.007Zn₄Ti₁₅O₃₆∶0.002Pr³⁺, 0.002Na⁺.     

气相中Sc+和Ti+与CS2反应的计算研究

以Sc⁺和Ti⁺与CS₂反应作为第一前过渡金属离子与CS₂反应的范例体系. 采用密度泛函(UB3LYP/6-311+G*)方法计算研究了Sc⁺和Ti⁺在基态和激发态与CS₂反应的反应机理. 全参数优化了反应势能面上各驻点的几何构型, 用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证. 计算了不同多重度下的反应交叉势能面. 确定了Sc⁺和Ti⁺与CS₂的反应为插入-消去反应, 找到了基态和激发态金属离子与CS₂反应的主要通道.     

Li4Ti5O12/CMK-3复合材料的制备及其作为锂离子电池负极材料的性能

将LiNO₃和Ti(OC₄H₉)₄填填充在有序介孔碳CMK-3 孔道中, 然后烧结合成了Li₄Ti₅O₁₂/CMK-3复合材料. 利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线衍射(XRD)对其结构和微观形貌进行了表征. 利用差热-热重分析(TG-DTA)测试复合材料中Li₄Ti₅O₁₂的含量. 利用充放电测试、循环伏安和电化学阻抗技术考察了复合材料作为锂离子电池负极材料的性能. 发现Li₄Ti₅O₁₂分布在CMK-3孔道中及其周围, 复合材料的高倍率充放电性能显著优于商品Li₄Ti₅O₁₂, 复合材料中Li₄Ti₅O₁₂的比容量明显高于除去CMK-3的样品(在1C倍率时比容量为117.8 mAh·g^-1), 其0.5C、1C和5C倍率的放电比容量分别为160、143 和131 mAh·g^-1, 库仑效率接近100%, 5C倍率时循环100次的容量损失率只有0.62%. 本研究结果表明CMK-3明显提高了Li₄Ti₅O₁₂的高倍率充放电性能, 可能是CMK-3特殊的孔道结构和良好的导电性减小了Li₄Ti₅O₁₂的粒径并提高了其电导率.     

Ba0.98Bi0.02(Ti0.9Zr0.1)1-xCuxO3陶瓷的介电性能、弛豫行为与结晶化学特性

采用固相合成法, Bi3+作施主掺杂A位, Cu₂₊作受主掺杂B位, 制备了Ba_0.98Bi_0.02(Ti_0.9Zr_0.1)_1-xCu_xO₃(x=0, 0.01, 0.02, 0.03)陶瓷样品。借助XRD、LCR等研究了该陶瓷的结构与介电性能。结果表明:当x=0.03时, 陶瓷样品出现第二相。通过GULP模拟, 缺陷偶极子的稳定性从低到高依次为:[2Bi_Ba^·+V_Ba"]、[2Bi_Ba^·+Cu_Ti/Zr"]、[Cu_Ti/Zr"+V_O^··], 结合实验可知:介电弛豫程度与晶体中缺陷偶极子的存在形式相关, 其中x=0.01时, 晶体中以[2Bi_Ba^·+Cu_Ti/Zr"]为主。随Cu₂₊掺杂量的增加, 介电常数增加, 介电常数与B位键价和呈反比变化、与八面体BO₆的体积呈正比变化。     

二维层状结构十钒酸盐[K(H2O)2Ni(H2O)6]2[V10O28]的合成及性质(英)

A novel heteropoly compound, containing two kinds of coordinated cations, [K(H₂O)₂Ni(H₂O)₆]₂[V₁₀O₂₈], has been synthesized through routine process and characterized by elemental analyses, IR, ⁵¹V NMR and single crystal X-ray diffraction. It crystallizes in the triclinic system, space group P1 with a=0.87382(17) nm, b=1.075 4(2) nm, c=1.111 1(2) nm, α=65.10(3)°, β=75.01(3)°, γ=70.63(3)°, V=0.884 8(3) nm³ and Z=1. The X-ray analysis reveals that the two kinds of coordinated cations are linked by three shared coordinated water molecules, and K⁺ cations coordinate with ten oxygen atoms: five of which come from V₁₀O₂₈^6- anion, the other five from water molecules. The title compound exhibits extended 2D array building up of V₁₀O₂₈^6- groups connected by ten-coordinated K⁺ cations. The hexahydrated nickel cations Ni(H₂O)₆²⁺ lie in neat apposition to three adjacent V₁₀O₂₈^6- clusters. CSD: 413271.     

新钽酸盐Ba3TiTa4O15的结构与介电性能

在BaO Ta2O5系统通过掺Ti4＋合成了新钽酸盐Ba3TiTa4O15,用粉晶XRD对其结构进行了分析,并测试了其烧结体的介电特性.结果表明:Ba3TiTa4O15在室温下属于填满型四方钨青铜结构,晶胞参数a=1.256 27(6)nm, c=0.395 86(4)nm; Ba3TiTa4O15在－35 ℃从铁电相转变为顺电相.     

The Primary Origin of Excellent Dielectric Properties of (Co,Nb) Co-Doped TiO2 Ceramics: Electron-Pinned Defect Dipoles vs. Internal Barrier Layer Capacitor Effect

(Co, Nb) co-doped rutile TiO₂ (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO₂ phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO₂ with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε′ ≈ 36,105 and a low loss tangent of tanδ ≈ 0.04 were achieved. The sample–electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoV_oTi complex defect. On the other hand, the substitution of TiO₂ with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent.     

类钙钛矿新铌酸盐Ba3La2Ti2Nb2O15的合成、结构与介电特性

为满足现代通信技术的小型化、集成化与高可靠性的迫切要求,探索具有高介电常数、低介电损耗与低温度系数的微波介电材料引起了材料科学、化学、物理和电子学等领域科学工作者的广泛关注,并已开发出复合钙钛矿结构[Ba(Zn1/3Ta2/3)O3]和钨青铜结构[Ba6-3xLn8+2xTi18O54]等实用化的高性.     

熔盐法制备Ca0.9La0.2/3Cu3Ti4O12陶瓷粉体及其介电性能研究

以CaCO3,CuO,TiO2,La2O3为反应物,NaCl,KCl为熔盐,通过熔盐法分别在700、750、800、850℃条件下合成Ca0.9La0.2/3Cu3Ti4O12陶瓷粉体。利用XRD和SEM分别对陶瓷粉体的物相结构和微观形貌进行了分析,并对其介电性能进行了测试。实验结果表明,随着合成温度的升高,陶瓷粉体的钙钛矿相含量逐渐增大,与传统固相法相比,熔盐法制备的粉体无团聚现象,耗时少。Ca0.9La0.2/3Cu3Ti4O12粉体制备的陶瓷在1 000℃烧结、测试频率在100 Hz~10 kHz时,获得优良的介电性能:介电常数大大超过104,介电损耗在0.1~0.47之间。     

微波介质材料BaEu2Ti4O12的交流阻抗谱表征

采用交流阻抗谱技术对微波介质材料BaEu2Ti4O12进行了表征。分析了lgε/lgf, Z″/Z′和Y′/lgf等图谱的特征与材料性能的关系.研究结果表明：1）阻抗谱测试得到的介电常数与所发表的微波测试结果有很好的一致性,高频下得到的介电常数实际上是晶粒和晶界的净结果,高质量烧结的材料应具有薄的晶界，因而应表现出较大的介电常数; 2）如果将材料从高温下缓慢降温或在O2气氛中退火，材料的导电性都会下降，其原因可以理解为这样处理的材料氧空位浓度降低，进而可以推测这有利于降低材料的介电损失.     

Bi4(Ti1/3Sn2/3)3O12掺杂BaTiO3基X8R陶瓷微观结构与介电性能

研究了Bi4(Ti1/3Sn2/3)3O12掺杂对钛酸钡基陶瓷微观结构和介电性能影响。结果表明,掺杂Bi4(Ti1/3Sn2/3)3O12后钛酸钡基陶瓷晶粒明显长大,同时烧结温度可由1 280℃降低至1 180℃。系统的介电性能和Bi4(Ti1/3Sn2/3)3O12的掺杂量有密切关系。当Bi4(Ti1/3Sn2/3)3O12的掺杂量从0.5mol%增加到2mol%,体系的居里峰被明显压低和展宽,当掺杂量为2mol%时居里峰变得不明显。当Bi4(Ti1/3Sn2/3)3O12的掺杂量从0.5mol%增加到2mol%,系统的居里温度由131℃升高至139℃。当Bi4(Ti1/3Sn2/3)3O12的掺杂量为1mol%时,钛酸钡基陶瓷介电常数为1 930,介电常数温度变化率为5%(-55℃),13%(134℃),-8%(150℃),满足X8R标准。     

类钙钛矿新铌酸盐Ba5NdTi2Nb3O18的合成、结构与介电特性

为满足现代通信技术的小型化、集成化与高可靠性的迫切要求,探索具有高介电常数、低介电损耗与低温度系数的微波介电材料引起了材料科学、化学、物理、电子等领域科学工作者的广泛关注,并已开发出复合钙钛矿结构Ba(Zn_(1/3)Ta_(2/3))O_3、钨青铜结     

反应气氛对Li4Ti5O12/C复合材料性能的影响研究

以葡萄糖为碳源,采用固相法制备了Li4Ti5O12/C复合材料。探讨了不同反应气氛（N2/O2）对材料物理性质及电化学性能的影响,并通过XRD、BET、电导率、电性能等测试手段对其进行表征。结果表明：氮气气氛中烧结的样品粒度、比表面积、电导率均比空气中烧结样品大。氮气中烧结样品的倍率性能优于空气中 烧结样品,在以0.1C倍率充放电时,首次放电比容量为166.8mAh/g。两样品1C时,经过50次循环容量保持率差别不大。     

类钙钛矿新铌酸盐Ba5LaTi2Nb3O18的合成、结构与介电特性

为满足现代通信技术小型化、集成化与高可靠性的迫切要求,探索具有高介电常数、低介电损耗与低温度系数的微波介电材料引起了材料科学、化学、物理和电子科学等领域科学工作者的广泛关注,并已开发出复合钙钛矿结构的Ba(Mg1/3Ta2/3)O3、Ba(Zn1/3Ta2/3)O3和钨青铜结构的Ba6-3xLn8+2x·Ti18O54及Ba2Ti9O20等实用化的高性能材料[1～7].这类材料均由氧八面体共顶连接,而且氧八面体内(B位)、外(A位)阳离子比例等于或略大于1,由此,我们推测在B位与A位阳离子比例略小于1的类钙钛矿结构中也极有可能存在具有优良介电性能的新材料,因此对通式为AnBn-1O3n(n=5,6,7,8)的系列新化合物进行了系统的合成、结构与介电性能研究[8,9].本文报道在BaO-La2O3-TiO2-Nb2O5体系中合成的具有5层类钙钛矿结构的新铌酸盐Ba5LaTi2Nb3O18,发现该材料具有较好的介电性能.     

锶、铈和镧共掺杂铈钛酸锶钡陶瓷的固溶性和介电性能的研究

采用冷压陶瓷技术,制备了(Ba1-x-0.02SrxLa0.02)(Ti1-yCey)O3(x=0.05,0.10,0.15;y=0.03,0.04,0.05)(BSLTC)陶瓷,通过X射线衍射(XRD)和介电温谱测试对BSLTC陶瓷的固溶性和介电性能进行调查。XRD结果表明,所有样品均为立方钙钛矿结构,La掺杂量为2%时,能够将(Sr,Ce)组合的固溶提高到(x=0.10,y=0.04)或(x=0.15,y=0.03)。介电结果表明,各样品的居里温度都在室温附近,介电峰明显宽化。其中,(x=0.05,y=0.03)组合的样品显示出最高的室温介电常数(ε’RT≈6000)和低介电损耗(tanδ<0.02),满足美国EIA"Y5V"高介电陶瓷材料指标。