还原气氛烧成Y5V型瓷粉的结构与介电性能

运用SEM、TEM、XRD等手段研究了掺杂组分对钛酸钡基Y5V陶瓷的结构和性能影响.结果表明:由于掺杂组分的存在,烧结情况得到了明显的改进.掺杂钛酸钡陶瓷的烧结包括固-固烧结和液-固烧结.Zr和稀土元素能够扩散进入钛酸钡晶格并促进固-固烧结,SiO2主要聚集在晶界并促进液-固烧结烧结.Nd5 聚集在晶界并促进针状颗粒生成,XRD的结果表明样品中有新相形成.由于掺杂的引入,材料的居里温度向低温方向移动,材料的介温曲线较纯钛酸钡材料的介温曲线更趋平坦.研究的结果还表明,由于在还原气氛中烧结,材料的介电损耗上升.     

B2O3蒸汽掺杂的中低温烧结Y-BaTiO3及其PTCR特性研究

通过B2O3蒸汽掺杂,Y-BaTiO3陶瓷的烧结温度大幅度降低．B2O3蒸汽掺杂后的样品,室温电阻率下降,升阻比提高．通过对氧化硼蒸汽掺杂样品的XRD分析研究表明,硼间隙可以在钛酸钡晶格中存在,硼间隙和／或相关缺陷络合物可以形成电子捕获中心,从而提高PTCR效应．     

精矿粉和Mn3O4制备MnZn功率铁氧体工艺研究

为了降低功率铁氧体的制备成本,采用传统氧化物陶瓷工艺,用精铁矿粉代替Fe2O3、用Mn3O4代替MnCO3制备出高性能功率软磁MnZn铁氧体.研究了精铁矿粉和Mn3O4制备MnZn铁氧体的固相反应及预烧温度、烧结温度和掺杂对样品磁性能的影响.实验结果表明:精矿粉经氧化生成的α-Fe2O3立即与Mn3O4反应生成MnZn铁氧体,使固相反应更完全;预烧温度为1100℃,烧结温度为1240～1280 ℃时样品性能最佳;适当的掺杂可降低样品的功耗.样品最佳性能如下:μi=2268;Bs=508 mT;Tc=227℃;Po=34.5 W/kg,综合性能达到日本TDK PC30材料性能水平.     

残余氧化硼对钛酸锶钡晶胞参数及相变温度的影响

研究了氧化硼掺杂（B2O3）烧结钛酸锶钡（Ba1-xSrxTiO3，x=0、0．4、1）陶瓷钙钛矿结构的稳定性、晶胞参数以及相变温度．结果表明，随着掺杂量的增加，钛酸锶钡仍保持原来的钙钛矿结构，但晶胞参数有所变化．晶格常数c与a并非单调变化，但轴比c／a单调递减而晶胞体积a^2c却单调增大．和未掺杂钛酸锶钡相比，掺杂钛酸锶钡陶瓷的相变温度有所升高．同一掺杂含量下，随着烧结温度的升高，因钛酸锶与钛酸钡相互固溶引起晶胞体积明显收缩，相变温度逐渐降低．但在同一烧结温度下，随着掺杂量的增加，相变温度几乎不变．说明硼离子半径虽然很小，氧化硼对钛酸锶钡晶胞参数的影响还是存在的，而且只能以填隙方式存在于晶胞，但其固溶能力非常有限．     

CBS玻璃和Mn2+复合掺杂BaTiO3陶瓷的电容量温度特性

研究了硼硅酸钙(CBS)玻璃不掺杂/掺杂时Mn2 浓度变化对钛酸钡陶瓷电容量温度特性的影响.结果表明,不掺CBS玻璃时Mn2 浓度变化对BT陶瓷电容量温度特性没有明显的影响,此时BT陶瓷超过X8R特性许可范围;而掺CBS玻璃时Mn2 浓度增大使电容量温度特性的高温峰持续增强,BT陶瓷容易满足X8R特性.掺CBS玻璃时Mn2 可使CBS析晶.BT陶瓷的电容量高温变化率和微观应力分数成正比例关系变化.条状第二相Ca4Mn4Si8O24的产生改变了BT系统的内应力结构是钛酸钡陶瓷电容量温度特性产生规律变化的主要原因.     

精矿粉和Mn3O4制备MnZR功率铁氧体工艺研究

为了降低功率铁氧体的制备成本，采用传统氧化物陶瓷工艺，用精铁矿粉代替Fe2O3、用Mn3O4代替MnCO3制备出高性能功率软磁MnZn铁氧体．研究了精铁矿粉和Mn，04制备MnZn铁氧体的固相反应及预烧温度、烧结温度和掺杂对样品磁性能的影响．实验结果表明：精矿粉经氧化生成的α—Fe2O3立即与Mn3O4反应生成MnZn铁氧体，使固相反应更完全；预烧温度为1100℃，烧结温度为1240～1280℃时样品性能最佳；适当的掺杂可降低样品的功耗．样品最佳性能如下：μi=2268；Bs=508mT；Te=227℃；P0：34．5W／kg，综合性能达到日本TDKPC30材料性能水平．     

B2O3蒸汽掺杂的中低温烧结Y-BaTiO3及其PTCR特性研究

通过B₂O₃蒸汽掺杂,Y-BaTiO₃陶瓷的烧结温度大幅度降低。B₂O₃蒸汽掺杂后的样品,室温电阻率下降,升阻比提高,通过对氧化硼蒸汽掺杂样品的XRD分析研究表明,硼间隙可以在钛酸钡晶格中存在,硼间隙和/或相关缺陷络合物可以形成电子捕获中心,从而提高PTCR效应。     

烧结气氛对 Er-Mg和 Er-Mn掺杂 BaTiO3陶瓷介电性能的影响

用固相法制备了Er-Mg和Er-Mn掺杂BaTiO3陶瓷,并研究烧结气氛对其微结构和电性能的影响.XRD显示样品经不同气氛烧结后均是赝立方相,在空气中烧结Er的固溶度约3.0m01%～4.0mol%,但还原气氛会抑制Er在BaTiO3中的固溶度,导致焦绿石相Er2Ti2O7出现.SEM显示Mg能抑制Er2Ti2O7晶粒的长大,而Mn促进此第二相的晶粒生长.研究表明,烧结气氛对受主离子的固溶度的作用将改变壳芯结构中壳/芯体积比,并且Mn离子的价态随气氛变化将移动居里点,从而显著影响电容变化率温度特性.采用适当的气氛烧结能够使两种介质都满足X8R要求.     

用精矿粉和Mn3O4制备高性能功率软磁MnZn铁氧体

用精矿粉代替Fe2O3、用Mn3O4代替MnCO3作为原材料，因为减少了Mn离子在反应中的变价机率，提高了配方中Mn离子的准确性，精矿粉的主要成分Fe3O4相变为α-Fe2O3的温度与Mn铁氧体生成温度接近，所以使固相反应更安全，能制备出高性能功率软磁MnZn铁氧体。适量的掺杂CaCO3、V2O5及Bi2O3可以进一步降低样品功耗；制备过程中，采取一些特殊工艺措施及适当烧结温度能进一步提高样品磁性能，使其综合性能基本达到日本TDK的PC30水平。     

固相法制备BaTiO3基细晶陶瓷粉体

通过传统的固相法制备BaTiO3基细晶陶瓷粉体，讨论了在预烧温度和烧结温度相同的情况下，探讨不同施主元素的添加量对陶瓷晶粒及电性能的影响；在预烧温度和烧结温度相同的情况下，探讨不同受主杂质对陶瓷晶粒及电性能的影响；在施、受主掺杂量及烧结温度相同的情况下，探讨不同的预烧温度对陶瓷晶粒及电性能的影响．为了制备高升阻比、晶粒细小的BaTi03陶瓷，选取的材料配方为Ba1.0Ti1.01O3＋0.4％（摩尔分数）Y2O3＋0.03％（摩尔分数）Mn（NO3）2＋2％S102，粉体在1200℃预烧，保温2h，样品在1280℃烧成。上电极后测得常温电阻率为4937Ω·cm，升阻比为7．116×10^3，温度系数为14．03％，居里温度为128．4℃．     

粘土作为廉价载体增强纳米TiO_2光生自由基的研究

在制备出粘土/nano-TiO2/活性炭复合陶瓷球基础上,应用ESR测试对其光生.OH\O2—.(羟基自由基和超氧阴离子自由基)信号进行研究。发现高黏度粘土中存在的Mn在烧结过程中被活性炭的还原性影响,生成了不常见的价态。此价态有利于纳米TiO2光生自由基过程中生成.OH\O2—.反应。此反应类似Fendon反应为:Mn2++H2O2→Mn3++.OH+OH—,测试结果显示.OH和O2—.的发生信号确实得到增强。     

LiMxMn2-xO4正极材料的表面改性机理研究

采用溶胶-凝胶包裹法对尖晶石LiMn2O4及其阳离子掺杂LiM0.1Mn1.9O4(M=Li，Ni)正极材料进行了表面改性研究．X射线衍射及电子探针线扫描分析表明，表面改性以后的晶粒仍为尖晶石结构，表面改性离子Co的浓度由表及里逐步减小．电解液溶蚀实验及电化学循环测试表明，表面改性后的正极材料LiM0.1Mn1.9O4的抗溶蚀性明显增强，循环性能优良．性能改善的原因是表面改性以后，尖晶石晶粒表层Mn^3 离子浓度降低，Mn^4 离子浓度大大增加，减少了Mn^3 发生歧化反应的机会．     

F掺杂影响LiMn2O4性能的机理研究

F掺杂可以提高锂离子电池正极材料LiMn2O4的初始容量,但使材料的循环性能变差。其原因是F的掺入降低了Mn的平均价态．Mn^3 的量增加,提高了材料的初始容量．但Mn^3 量的增加也加剧了Mn的溶解和Jahn—Teller畸变,使材料的循环性能变差。F掺杂虽然降低了材料的循环性能．但提高了材料的初始容量,为改善阳离子掺杂方法的不足提供了一条可能的解决途径。     

Effect of Cerium Doping on Microstructure and Dielectric Properties of BaTiO3 Ceramics

A solid state reaction method was used to synthesize barium titanate (BT) and barium cerium titanate (BCT) ceramics at sintering temperature of 1473 K for 4 h. The effect of cerium (Ce) on the structure, microstructure and dielectric properties of BCT was investigated. The scanning electron microscopy (SEM) investigations revealed that the grain size increases with increasing Ce content. The X-ray diffraction (XRD) patterns showed mostly the BT phase, where the lattice parameter decreased with the addition of Ce. The temperature dependence of dielectric constant showed decrease in the phase transition temperature with higher Ce content. The dielectric constant decreased slightly with increasing frequency. The direct current (dc) density-voltage characteristics of the ceramics showed ohmic behavior for both the BT and BCT. As the temperature increased, the dc resistivity of the ceramics decreased. The activation energy increased with increasing Ce content.     

Influence of microstructure on dielectric properties of Nd-doped barium titanate synthesized by hydrothermal method

Nd-doped barium titanates were successfully synthesized via a hydrothermal route. The as-prepared barium titanate was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transformation infrared spectroscopy (FTIR), and Vis–NIR spectroscopy respectively. The results show that pure and Nd-doped barium titanate powders have cubic perovskite structure. After sintering at a temperature of 1,250 °C for 2 h, the phase compositions of all barium titanate are tetragonal phase structure. Vis–NIR spectra well confirmed that Nd³⁺ have been doped into barium titanate. The particle diameters of Nd-doped barium titanate powders and ceramics become samller with the increase of Nd³⁺ content. When Nd/Ba molar ratio is 0.02, the dielectric loss (0.0008) of the powder measured at 1 MHz and room temperature dramatically decreases by 99 % comparing with pure barium titanate (0.083) and shows frequency independence with the frequency increasing from 40 Hz to 1 MHz. The dielectric constant and dielectric loss are 436 and 0.09 after sintering. The Nd-doped BaTiO₃ show an improvement in the dielectric quality which possess a decreased sensitivity to frequency for both the dielectric constant and dielectric loss. Such improvements are of potential importance for high energy density and low loss.     

Effect of sintering condition on microstructure and dielectric properties of BSTN composite ceramics

The effect of sintering condition on the phase composition, microstructure and dielectric properties of barium strontium titanate niobate (BSTN) composite ceramics, in which the perovskite phase and the tungsten bronze phase coexisted, was investigated by XRD, SEM and LCZ Meter. The results show that more Sr²⁺ ions dissolved from the grain boundaries into the crystal lattice of the pervoskite phase and the tungsten bronze phase, especially, into the lattice of the pervoskite phase with the increasing of sintering temperature and sintering time, respectively. So the Curie temperature point decreases with the increasing of sintering temperature. The crystal growth rate of the tungsten bronze phase is higher than that of the perovskite phase in BSTN composite ceramics as the sintering temperature increases. The reasonable sintering temperature is about 1275 °C for BSTN composite ceramics. The activation energy to setting up polarization in BSTN composite ceramics increases with the increase of the applied frequency.     

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.     

Defect profile and electrical properties of Nb2O5-doped BaTiO3 materials

This work deals with the changes in properties induced by the incorporation of donor ions into the BaTiO₃ lattice. We focused on the relationship between microstructural development and the defect profile of Nb-based compositions around the semiconducting–insulating transition at 0.3% of donor oxide. The results indicated that the defect structure that developed controlled both microstructural and electrical properties. On sintering slightly doped BaTiO₃, large semiconducting grains and low barium vacancy concentration were detected. This behavior was explained by considering an electronic compensation mechanism based on dopant incorporation. Further dopant addition led to a dramatic grain-growth inhibition and a clear transition to a material with higher resistivity. In addition, an extraordinary generation of barium vacancies was observed. Heavily doped materials consisted of core-shell structures with a Ti-rich phase surrounding BaTiO₃ grains. This phenomenon originated a significant grain-boundary barrier layer response.     

Structural characterization of 0.5PbMg1/3Nb2/3O3-0.5BaxPb(1−x)TiO3 powders

The present work reports the effects caused by barium on phase formation, morphology and sintering of lead magnesium niobate-lead titanate (PMN-50PT). Ab initio study of 0.5Pb(Mg_1/3Nb_2/3)O₃-0.5(Ba_xPb_(1−x)TiO₃) ceramic powders, with x = 0, 0.20, and 0.40 was proposed, considering that the partial substitution of lead by barium can reestablish the equilibrium of monoclinic-tetragonal phases in the system. It was verified that even for 40 mol% of barium, it was possible to obtain pyrochlore-free PMN-PT powders. The increase of the lattice parameters of PMN-PT doped-powders confirmed dopant incorporation into the perovskite phase. The presence of barium improved the reactivity of the powders, with an average particle size of 120 nm for 40 mol% of barium against 167 nm for the pure sample. Although high barium content (40 mol%) was deleterious for a dense ceramic, contents up to 20 mol% allowed 95% density when sintered at 1100 °C for 4 h.