钛酸铋钙和稀土复合掺杂对BaTiO3陶瓷微结构和介电性能的影响

研究了稀土及CaBi4Ti4O15（CBT）的复合掺杂对BaTiO3（BT）陶瓷微结构及介电性能的影响。结果表明：单独添加CBT使晶粒细化,促进了陶瓷的烧结致密化,居里温度随着CBT含量的增加（≤0．5mol％）而逐渐移向高温端;当CBT含量由0．3mol％增加到0．5mol％时,BT陶瓷的电容量变化率逐渐减小;当CBT含量超过0．5mol％时,电容量变化率又增大。在BaTiO,CBT（BT—CBT）基础上单独添加1．0mol％La2O3,四方率减小,居里点移向低温端;保持La2O3掺杂量不变,随着CeO2含量的增加,BT—CBT陶瓷的晶胞体积呈现先减小后增大的变化趋势,四方率保持不变;1．0mol％La2O3和0．01mol％CeO2掺杂BT—CBT（0．5m01％）陶瓷在-55℃和125℃的电容变化率分别为-14．78％和-11．44％。完全符合EIAX7R标准,有望用于X7R型多层陶瓷电容器的制备。     

常用贴片电容器介绍(上)

1.贴片多层陶瓷电容器贴片多层陶瓷电容器(Multilayer Ceramic Capacitor/MLCC)简称贴片电容器,是由印好电极(内电极)的陶瓷介质膜片以错位的方式叠合而成,经过一次性高温烧结形成陶瓷芯片,再在芯片的两端封上金属层(外电极),     

WO3对碳载EMD催化氧还原活性的影响

研究了助催化剂三氧化钨(WO3)对电解二氧化锰(EMD)催化性能的影响.通过球磨制备5种WO3含量的EMD复合催化剂,进行XRD、SEM和电化学性能测试.WO3影响了EMD的孔隙率,添加适量的WO3可改善EMD的催化性能.添加WO3催化剂的氧还原电位较未添加WO3催化剂提前0.02 V.当电压为-0.15 V时,EMD、( MnO2)33( WO3)0.7、(MnO2)33(WO3)1、( MnO2)33 (WO3)1.3及(MnO2 )33( WO3 )1.5的氧还原电流分别为:-0.21 mA、-0.35 mA、-0.85 mA、-0.53 mA和-0.08 mA,表明随着WO3添加量的增加,EMD的催化性能先提高,后下降.EMD、( MnO2)33( WO3 )0.7、( MnO2 )33( WO3)1、(MnO2)33 (WO3)1.3及(MnO2)33 (WO3)1.5制备的电池,放电平台分别为1.05 V、1.08 V、1.21 V、1.14 V和0.98 V;催化活性顺序为:(MnO2)33(WO3)1＞ (MnO2)33(WO3)1.3＞(MnO2)33(WO3)0.7＞EMD＞ (MnO2)33(WO3)1.5.     

MnO_x-WO_3/TiO_2用于NH_3选择性催化还原NO_x的性能与抗SO_2毒性研究

研究了Mn-W/TiO2用于NH3选择性催化还原NOx体系的催化反应性能,探索了不同温度条件下该催化剂对抗不同SO2浓度的抗毒性能。结果显示WO3能够增加活性酸中心的数量和酸性,是MnOx/TiO2非常有效的助催化剂。在气体体积空速(gaseous hourly space velocity,GHSV)为18900h-1时100～350℃范围内,Mn-W/TiO2催化剂还原NOx的转化率高达80.3%～99.6%,N2选择性达100%～98.7%。当反应气中有0.01%SO2和6%H2O时,120℃NOx转化率可维持在98.5%,当SO2浓度超过0.01%时,则需将反应温度升高到250℃以上才可消除其干扰,而当SO2浓度高达0.07%时,300℃下转化率可长期维持在99%,达到了商用V-W/TiO2催化剂的水平。对于NH3选择性还原NOx体系Mn-W/TiO2显示了极好的催化性能,是目前抗SO2毒性最强的催化剂之一。试验发现,低温条件下,SO2对Mn-W/TiO2催化剂的影响是可逆的,随着反应温度的提高,活性将自然恢复。     

Ag/Al2O3催化剂上C3H6选择性还原脱除烟气中NO

在Autosorb-1-C物理化学吸附仪上测定了Ag/Al2O3催化剂的比表面积、孔容等物理特性,并采用该催化剂和C3H6还原剂对NO脱除过程进行了试验研究。结果表明,在适宜的反应温度和空速范围内,所制备的催化剂具有良好的脱氮活性;除温度和空速外,催化剂中Ag的负载量、C3H6与NO的摩尔比、烟气中氧含量和NO初始浓度等因素对催化剂反应性能有较大影响。试验确定的最佳反应温度为450℃~500℃,最佳Ag负载量为2%左右。     

K0.5Na0.5NbO3掺杂对BaTi03陶瓷介电性能的影响

采用固相反应法制备了（K0.5Na0.5）Nb03-BaTiO3。体系陶瓷。借助XRD、SEM和阻抗分析仪研究了掺杂（K0.5Na0.5）Nb03（简写为KNN）对陶瓷微结构及介电性能的影响。结果表明,掺杂KNN的陶瓷均呈单一的钙钛矿结构;掺杂KNN能促进陶瓷的烧结和提高陶瓷的致密度。,BaTiO,陶瓷在高温端的电容变化率随KNN量的增加显著减小。陶瓷晶粒尺寸随KNN的增加（KNN掺杂量≤3m01％）逐渐变小。掺杂3mol%6和5m01％KNN的BaTiO3陶瓷满足EIAX7R特性。     

低温NH3选择性催化还原脱硝催化剂MnFexCe1-xTiO2抗硫再生性能研究

通过共沉淀法制备了MnFexCe1-xTiO2催化剂,以NH,为还原剂,考察了催化剂的脱硝性能及抗硫再生性能。结果表明,Mn1Fe09Ce0．1／TiO2催化剂表现出最佳的脱硝活性和优良的抗硫性能,在140℃时NO转化率可达到100％。在烟气中通入的SO2浓度小于等于80mg／m3时,催化剂只发生可逆性中毒,当SO2浓度大于80mg／m3时,在催化剂表面会生成硝酸盐及硫酸盐等物质导致不可逆失活,但中毒失活催化剂在经水洗后可实现再生,NO的转化率可基本恢复至新鲜催化剂水平。     

低温NH_3选择性催化还原脱硝催化剂Mn_1Fe_xCe_(1-x)/TiO_2抗硫再生性能研究

通过共沉淀法制备了Mn1Fe1-xCex/TiO2催化剂,以NH3为还原剂,考察了催化剂的脱硝性能及抗硫再生性能。结果表明,Mn1Fe0.9Ce0.1/TiO2催化剂表现出最佳的脱硝活性和优良的抗硫性能,在140℃时NO转化率可达到100%。在烟气中通入的SO2浓度小于等于80mg/m3时,催化剂只发生可逆性中毒,当SO2浓度大于80mg/m3时,在催化剂表面会生成硝酸盐及硫酸盐等物质导致不可逆失活,但中毒失活催化剂在经水洗后可实现再生,NO的转化率可基本恢复至新鲜催化剂水平。     

稀土掺杂对BaTiO3陶瓷结构和性能的影响

综合了国内外稀土改性BaTiO3陶瓷的相关研究报导,着重阐述了稀土掺杂对BaTiO3陶瓷电阻率和介电性能的影响规律,并分析了其作用机理。稀土元素作为BaTiO3陶瓷常见的添加剂,可以降低陶瓷电阻率,开发BaTiO3陶瓷半导体领域的应用;可以提高介电常数和改善电容量温度特性,使Ba-TiO3陶瓷满足X7R或X8R特性,可以应用于高压高介电陶瓷电容器中。     

烧结工艺对BaTiO3基PTCR电阻-温度系数的影响

研究了在制备掺杂Nb2O5的BaTiO3基PTC热敏电阻时,烧结工艺对电阻-温度系数的影响。探讨了通过烧昝工艺提高电阻-温度系数的方法与途径,并通过性能的测试对比以及利用SEM分析,对烧结工艺对电阻-温度系数影响的作用及机理进行了初步讨论。     

压电陶瓷的制备与特性研究

研究了不同的制备工艺对BaTiO3纯相的影响以及钛锆酸钡陶瓷的特性。实验结果表明 :在 10 0 0℃以上条件下制备的BaTiO3陶瓷的相组成较为单一。 110 0℃条件下制得的纯相BaTiO3比在 10 0 0℃条件下的钙钛矿型结构较好 ,c/a较大。适量掺Zr可控制晶体的四方度和有害的焦绿石相的含量 ,可改善其性能     

CaTiO3-NdAlO3系微波介质陶瓷的研究进展

综述了具有中等介电常数的CaTiO3-NdAlO3微波介质陶瓷在晶体结构、制备及反应过程、介电性能等方面的研究进展,总结了该体系微波介质陶瓷研究中存在的问题及其发展趋势。     

CaTiO3-NdAlO3系微波介质陶瓷的研究进展

综述了具有中等介电常数的CaTiO3-NdAlO3微波介质陶瓷在晶体结构、制备及反应过程、介电性能等方面的研究进展,总结了该体系微波介质陶瓷研究中存在的问题及其发展趋势。     

改性对钛酸钡陶瓷介电常数的影响

钛酸钡(BaTiO3)陶瓷以其优异的铁电、压电、绝缘性能广泛应用于体积小、容量大的电子器件材料领域,为解决钛酸钡(BaTiO3)陶瓷在一定的工作温度区间介电常数呈现不稳定变化问题,对其进行改性,着重研究稀土掺杂改性对BaTiO3陶瓷介电性能的影响,并对目前存在的问题提出了解决的方法。     

Microwave Dielectric Properties of Ferroelectric BaTiO3 Thin Film

The dielectric properties of c-axis epitaxial BaTiO₃ thin film on LaAlO₃ are investigated at frequencies of 0.5–30 GHz. For the measurements, interdigital capacitors with the Au/Ti electrode configurations of five fingers pairs that are 15 m wide and spaced 2 m apart are prepared by photolithography and lift-off patterning. Finger length varies from 20 to 80 m. The capacitance of epitaxial BaTiO₃ films exhibited no frequency dependence up to 10 GHz with the exception of slightly upward tendency of capacitance in BaTiO₃ film with a finger length of 80 m due to the self resonant frequency at 20 GHz. The Q-factors of the capacitors, defined as Q = 1/CR, are decreased up to 10 GHz with increased frequency. At 10 GHz, the BaTiO₃ film has a tunability [defined as k(V) = [C(0)–C(V)]C(0)] of 1.5% at 15 V, a loss tangent of 0.2 at room temperature. The small tunability can be interpreted as a result of in-plane compressive stress of BaTiO₃ film exhibiting large dielectric anisotropy. For the improvement of tunability and dielectric loss in the interdigital BaTiO₃ capacitor, the tetragonality (c/a) of epitaxial BaTiO₃ film and design of interdigital capacitor should be modified.     

Growth and Dielectric Properties of Ferroelectric BaTiO3 Thin Films for Cantilever-Type Microsensors

ABSTRACT

Ferroelectric BaTiO₃ (BTO) thin films were deposited on Si, silicon-on-insulator (SOI) and MgO substrates by pulsed laser deposition. The orientations of the films, polycrystalline and epitaxial phase, were controlled by the lattice mismatch between the BTO film and substrates. The structural properties and surface morphologies were examined using X-ray diffractometer and atomic force microscope. The dielectric properties of BTO films were investigated using metal-ferroelectric-metal (MFM) and interdigital co-planar capacitors. Conductive oxide layers, SrRuO₃(SRO) and La_0.5Sr_0.5CoO₃ (LSCO), were grown on Si and SOI substrates as bottom electrodes. For MFM capacitors based on Au/BTO/SRO/Si and Au/BTO/LSCO/SOI layer structures, a little asymmetric capacitance-voltage curves were obtained with about 36% capacitance tunability. The remanent polarizations were about 21 μC/cm² and the coercive fields were about 71 kV/cm. For an interdigital capacitor based on Au/BTO/MgO layer structure, a little lossy capacitance-voltage curve was obtained with about 64% capacitance tunability.     

Dielectric properties of BaTiO3-based ceramics measured up to GHz region

A new measuring method and analyzing procedure were proposed to determine the complex dielectric constant of materials with relatively high dielectric constant by a lumped impedance measurement using impedance analyzer. Samples used for the measurement were (Ba_0.6Sr_0.4)TiO₃ (BST) and Ba(Zr_0.25Ti_0.75)O₃ (BZT) ceramics. Micro planar electrodes were formed on the surface of samples by electron beam lithography followed by lift-off method. Complex admittances of these samples were measured up to 3 GHz at different temperatures. Electromagnetic simulations were performed for determining the relative dielectric constant and dielectric loss. The complex dielectric constant vs frequency curves of Ba(Zr_0.25Ti_0.75)O₃ showed a broad dielectric relaxation, while that of (Ba_0.6Sr_0.4)TiO₃ was almost flat up to 3 GHz on high-temperature side of T _m at which dielectric constant shows maximum value. Dielectric dispersion properties were discussed from the viewpoint of diffuse phase transition in ferroelectrics.     

高介碳酸钡陶瓷沿面闪络伪火花开关的研究

为了满足脉冲功率技术和脉冲电流试验技术对放电开关的要求,笔者设计了BaTiO3高介电常数的电介质沿面闪络伪火花开关的触发装置。通过对表面放电触发器的实验发现:在伪火花开关的工作气压范围内,高介沿面闪络触发器显示出很强的电荷发射能力和快速的电荷注入能力,在气压为7 Pa时,触发器能够在30 ns内释放1.5μC,触发电流的上升陡度为1.2×1011A/s,发射的电子数达到9.4×1012。对自放电电压为28 kV的伪火花开关,可靠工作的最低电压可降低到130 V,放电时延为35～100 ns,最小抖动为6～25 ns。