铌酸锶钡/钛酸锶钡介电常数预测模型研究

首次应用粉末-溶胶工艺合成出铌酸锶钡/钛酸锶钡复相陶瓷(SBN/SBT)。以Clausius(克劳修斯)-Mosotti(莫索缔)方程为基础,采用混合对数法则,通过实验得到的复合材料的晶格参数和铌酸锶钡、钛酸锶钡的理论极化率,建立了描述铌酸锶钡/钛酸锶钡复相陶瓷的介电常数预测模型,通过数学模型得到的预测数值与实验数值吻合。     

铌酸锶钡/钛酸锶钡复相陶瓷制备新工艺研究

本文以钛酸四丁酯等配制溶胶前驱体溶液,通过控制前驱体溶液中各组分的配比成功制备了粘稠的溶胶溶液,以悬浮传统固相烧结工艺制备的微米级铌酸锶钡陶瓷粉体,在超声分散等的作用下形成均匀凝胶,最后成功制备出复相陶瓷坯体。采用X射线及扫描电镜对其进行表征,同时对其制备工艺及烧结制度进行了分析。结果表明:此工艺具有工艺简单,成本低,两相固溶均匀,且在一定程度上能够抑制在烧结过程中晶粒异常长大等优点,为科研工作者提供了一条新的工艺路线。     

复相陶瓷(0.5BaO0.5SrO)[(1-y)TiO2yNb2O5]的介电性能研究

通过对组成进行一定的过量控制，利用传统陶瓷工艺，成功制备了具有钙钛矿相钛酸锶钡固溶体和钨青铜相铌酸锶钡固溶体两相稳定共存的(0.5BaO0.5SrO)[(1-y)TiO2yNb2O5](BSTN)复相陶瓷.用Riguaku D/max-2400型X射线衍射仪和KEITHLEY 3330阻抗分析仪对所得样品的相结构状态及介电性能进行了测试.结果表明：Y值在0.1～0.7之间的BSTN复相陶瓷为钙钛矿相和钨青铜相两相稳定共存的复合相；在该范围以外，则为单一相的钛酸锶钡与Nb或铌酸锶钡与Ti的固溶体.复相陶瓷的介电性能取决于钙钛矿相和钨青铜相的相对含量及其固溶度，当组成y约为0.7时，介电常数达到最大值；随测试频率的提高，介电常数和损耗降低.复相陶瓷中钨青铜相的铁电/顺电相转变温度与钨青铜相中固溶TiO2量相关，随固溶量增加，转变温度降低.同时，受复相陶瓷中钙钛矿相的影响，随钙钛矿相相对含量的增加，转变温度升高；钨青铜相的最低铁电/顺电相转变温度出现在约110℃，比Sr0.5Ba0.5Nb2O6下降约240℃.     

复相陶瓷

从陶瓷发展历史过程与相应社会发展需求说明复相陶瓷的研究是当前结构陶瓷发展的重要研究方向之一。简要介绍了复相陶瓷的组份设计的主要依据是物理化学性能上相互匹配,以及制备科学和工艺方案选择合理性。从近年来对复相材料的研究发展举出若干成功例子,其中以纳米级复合材料性能更佳,可能是发展高强高韧结构材料的一个主要方向。最后对复相陶瓷的强化增韧机理加以综述。     

锆溶胶制备及其对刚玉莫来石复相陶瓷性能的影响

采用溶胶-凝胶法合成了锆溶胶,并在刚玉-莫来石质材料中引入ZrO2,分析了ZrO2溶胶对刚玉-莫来石复相陶瓷性能的影响特征。研究结果表明,ZrO2在主体材料中形成纳米包裹薄膜,ZrO2的分布可控和均匀掺入,不仅提高复相陶瓷的抗热震性、高温强度及蠕变性,而且还使微观结构可控、晶粒尺寸均匀。加入ZrO2溶胶产生氧化锆粒子的应力诱导相变增韧和微裂纹增韧是刚玉-莫来石质材料热震稳定性提高的主要原因。     

硅溶胶对刚玉莫来石复相陶瓷的性能影响

采用溶胶-凝胶法在刚玉-莫来石质材料中引入活性硅溶胶(SiO2),分析了硅溶胶对刚玉-莫来石复相陶瓷性能的影响机制。研究结果表明,SiO2在主体材料中形成纳米包裹薄膜,SiO2的分布可控、掺入均匀,从而提高了复相陶瓷的抗热震性、高温强度及蠕变性。加入SiO2溶胶产生的莫来石反应化和微裂纹增韧是刚玉-莫来石质材料热震稳定性提高的主要原因。     

纳米复相陶瓷

纳米复相陶瓷以其优异的性能受到大家的关注，成为陶瓷研究领域的研究热点。本文在介绍纳米复相陶瓷分类、材料设计和制备的同时，着重阐述了纳米复相陶瓷中纳米颗粒对材料的显微结构和性能的影响。     

纳米复相陶瓷

本文简要介绍了纳米复相陶瓷、纳米复相陶瓷力学性能，着重分析了纳米Ｓｉ３Ｎ４－ＳｉＣ复相陶瓷显微结构特点，同时展望了今后纳米复相陶瓷的研究重点。     

钛酸铜锶钡陶瓷晶相结构及介电性能研究

采用溶胶-凝胶法制备(Ba0.5Sr0.5)1-xCuxTiO3高介电性能陶瓷,用X射线衍射和LCR分析仪对不同x取值和烧结温度制备陶瓷的晶相组分和介电性能进行分析对比,结果表明,x=0.1可以得到比较好的固溶体;随着Cu2比例上升,陶瓷中出现氧化铜杂相;并且,烧结温度升高,陶瓷中氧化铜相含量也增加.氧化铜相含量的增加使陶瓷的介电系数获得明显提升,可达104数量级,但与此同时,氧化铜相也使陶瓷的介电损耗有所增大.     

纳米陶瓷及其纳米复相陶瓷的研究现状

综述了纳米陶瓷和纳米复相陶瓷的的研究现状．探讨了纳米陶瓷的力学性能及其热喷涂纳米陶瓷涂层存在的问题．分析了纳米复相陶瓷的增韧机理，为纳米陶瓷的研究和应用提供了理论依据。     

溶胶-凝胶法制备TiO_2粉体及掺杂锰对光催化性影响

提出了以钛酸四丁酯为前驱物,采用溶胶-凝胶法制备TiO2粉体。以MnSO4.H2O为锰源,制备锰掺杂的Mn-TiO2光催化剂,在600℃、焙烧2h条件下制备了不同浓度掺杂锰的TiO2纳米粉体。通过X射线粉末衍射仪(XRD)、粒度分析仪和分光光度计等表征方法系统分析二氧化钛的结构,并在此基础上深入探讨了二氧化钛的晶体结构、比表面积及掺杂等因素对其光催化活性的影响。     

The Effects of Low Oxygen Activity Conditions on the Phase Equilibria and Cation Occupancy of Strontium Barium Niobate

Strontium barium niobate (SBN) is a tungsten bronze family ferroelectric which shows promising thermoelectric properties under reducing conditions. It is found here that the enhanced electrical conductivity of oxygen‐deficient SBN correlates with the formation of a NbO₂ secondary phase. The effects of the reducing environment and the NbO₂ phase formation are studied via a detailed defect chemistry analysis. Increasing amounts of the NbO₂ phase are accompanied by an interesting mechanism where the A‐site occupancy of the SBN matrix increases. The resulting donor defects source the large carrier concentrations which cause the enhanced electrical conductivity necessary for thermoelectric performance. In investigation of the phase equilibria, it is found that a solid solution between (Sr_0.6,Ba_0.4)Nb₂O₆ and (Sr_0.6,Ba_0.4)_1.2Nb₂O₆ exists and that the A‐site filling is found to occur at more modest reduction conditions in Sr‐ and Ba‐rich compositions. Finally, thermogravimetric analysis of the reoxidation process is performed, and the results suggest that the A‐site filling is compensated ionically. Not only do the presented results explain the enhanced electrical conductivity of oxygen‐deficient strontium barium niobate but also modification of the site occupancies by reduction and reoxidation may widen the design space for property modification in tungsten bronze‐structured materials in general.     

溶胶-凝胶法制备TiO2粉体及掺杂锰对光催化性影响

提出了以钛酸四丁酯为前驱物,采用溶胶-凝胶法制备TiO2粉体。以MnSO4·H2O为锰源,制备锰掺杂的Mn—TiO2光催化剂,在600℃、焙烧2h条件下制备了不同浓度掺杂锰的TiO2纳米粉体。通过x射线粉末衍射仪（XRD）、粒度分析仪和分光光度计等表征方法系统分析二氧化钛的结构,并在此基础上深入探讨了二氧化钛的晶体结构、比表面积及掺杂等因素对其光催化活性的影响。     

Fabrication of Optically Transparent and Electrooptic Strontium Barium Niobate Ceramics

The tetragonal tungsten bronze (TTB) type of Sr _x Ba_{1− x} ^m Nb₂O₆ (SBN) (0.5 ≤ x ≤ 0.75) was synthesized by a mixed-oxide route. Using the two-step densification process of pressureless sintering followed by oxygen HIPing, transparent ceramics were successfully fabricated. Microstructural, dielectric, optical, and electrooptic properties were investigated. All single-phase TTB-type SBN showed the characteristics of relaxor ferroelectrics. The extinction coefficients of the sample with the highest transparency were calculated from transmission spectra to be 30.4, 5.8, and 2.4 cm⁻¹ at 600, 1450, and 2000 nm, respectively. The linear electrooptic coefficients for SBN55, r ₃₃ and r ₁₃, were 46 × 10⁻¹² and 21 × 10⁻¹² m/V at 633 nm, respectively.     

Diffuse Phase Transition of Tantalum-Bearing Strontium Barium Niobate

The dielectric constants, ε' and ε", of tantalum-bearing strontium barium niobate (SBNT) ceramics were measured as functions of temperature and frequency. The phase transition of SBNT became ambiguous by adding Ta and the apparent Curie temperature determined from the maximum of ε' had a linear relation with the axial ratio c/a. A dielectric loss peak was observed in the phase transition region of SBNT, and its peak frequency increased with temperature. The loss peak was attributed to dielectric relaxation by the jump between two states with different polarizing directions as a preliminary phenomenon of the phase transition. A model based on the local variation from one unit cell to the next rather than the macroscopic compositional fluctuation in the crystal was proposed for the mechanism of diffuse phase transition.     

Sr1-xBaxNb2O6钨青铜铁电陶瓷的结构与介电性能研究

通过固相反应法合成了Sr1-xBax Nb2O6(SBN)钨青铜型铁电陶瓷,并对其结构、介电性能进行了系统的研究.结果表明在所研究的成分范围内,SBN陶瓷均形成了四方钨青铜相,但是SBN25陶瓷的主相为焦绿石相,其他3种成分的SBN陶瓷均为四方钨青铜单相.SBN陶瓷均存在一个明显的弥散介电峰,峰值温度随x的增加从室温(SBN25)升高到130℃左右(SBN60);同时峰值温度随频率往高温偏移,为典型的弛豫铁电相变.     

Fabrication and Mechanical Property of BaNb2O6/Al2O3 Composite Ceramics

为研究功能材料对结构陶瓷微观结构和力学性能的影响,将铁电相 BaNb2O6引入到 Al2O3陶瓷中,分别采用无压和热压烧结技术于 1350 ℃制备 BaNb2O6/Al2O3复相陶瓷,对其物相组成、微观结构和力学性能进行了研究。结果表明：BaNb2O6与 Al2O3经过高温烧结能够稳定共存,BaNb2O6的加入促进了 Al2O3陶瓷的烧结。BaNb2O6加入量为 10%（体积分数）时,1350 ℃无压烧结和热压烧结制备的 BaNb2O6/Al2O3复相陶瓷的致密度、抗弯强度和断裂韧性分别为 94.6%、214MPa、2.28 MPa m1/2和 99.3%、332 MPa、3.55MPa m1/2。当裂纹扩展遇到 BaNb2O6晶粒时发生穿晶断裂,但在晶粒内部出现裂纹偏转,说明铁电相 BaNb2O6晶粒内部的微观结构有助于陶瓷的强韧化。     

Effect of Barium Titanate on Microstructural Evolution and Properties of Lead Zinc Magnesium Niobate Ceramics

BaTiO₃ (BT) addition vastly alters the dielectric behavior of lead zinc magnesium niobate (PZMN) relaxor ferroelectrics. Heat treatment, including the sintering process, influences the dielectric properties through changes in the distribution of heterogeneous compositions and in the extent of diffused phase transition. With more than 15 mol% BaTiO₃ addition, two cubic phases composed of Ba-rich and Ti-rich PZMN substances exist. The destruction of the BaTiO₃ phase and reconstruction of Ba-rich and Ti-rich regions are initiated during heat treatment, and the extent of destruction and reconstruction determines the dielectric properties of the PZMN ceramics. The BT-rich PZMN phase, which occurs with higher BaTiO₃ addition, plays a less important role in the present investigation.