金属Ni/石墨/BaTiO3基复合PTC材料的研究

探讨了降低BaTiO3基的PTC陶瓷室温电阻率的新途径，即在BaTiO3基的VIE陶瓷配方中加入石墨或金属Ni。目的是将石墨或金属Ni优良的导电性和BaTiO3陶瓷的PTC效应相结合，制备出具有较低室温电阻率又有较好PTC效应的复合材料。通过对大量实验和数据分析。优化了实验配方和工艺条件．获得了性能良好的复合PTC材料。     

双施主掺杂对PTC陶瓷性能的影响

为了提高PTC陶瓷整体性能,本文用正交法对高温PTC进行了双施主Nb2O5和La2O3掺杂配比的实验,优选了配方,其中La2O3的摩尔分数应该控制在0.0006～0.0008之间,Nb2O5控制在0.0005～0.0007之间较好。同时研究了双施主掺杂与单施主掺杂分别对高居里点PTC陶瓷性能的影响。     

锰铬体掺杂对氧化铝陶瓷绝缘子性能的影响

为改善氧化铝陶瓷绝缘子的沿面耐压能力开展体掺杂实验研究。以95％(质量分数,下同)氧化铝陶瓷瓷料为基料,选择Cr2O3和MnCO3作为添加剂制备掺杂样品,并对该陶瓷样品进行了性能参数测试及沿面耐压、体击穿、金属化等实验研究。结果表明：与目前常用的95％氧化铝陶瓷相比,锰铬掺杂氧化铝陶瓷具有更优越的表面性能。同一条件下,掺杂样品沿面耐压能力更强。采用新设计金属化配方及工艺,锰铬掺杂瓷样品金属化效果更佳。同时,体掺杂对氧化铝陶瓷体性能(体耐压水平、抗折强度等)没有十分明显的影响。进一步分析表明：锰铬掺杂降低了氧化铝陶瓷的表面电阻率和表面二次电子发射系数,从而使其具有更强的沿面绝缘能力。此外,在对陶瓷样品组成结构分析的基础上,就锰铬掺杂对氧化铝陶瓷的改性机理进行了探讨。     

晶界势垒和缺陷对PTC效应影响的研究

为了适应市场对低压集成电路过流保护作用的PTC热敏陶瓷的低阻化要求,采用还原-再氧化的烧结工艺来制备多层片式PTC热敏陶瓷.本文主要研究了(Ba1.022-xSmx)TiO3基陶瓷在还原气氛中1200℃烧结30 min并在800℃再氧化热处理后其室温电阻率随施主掺杂浓度的变化关系,以及冷却速率对该样品PyTC效应的影响.从氧化物半导体理论出发,阐述了在还原再氧化过程中该陶瓷的缺陷模型和晶界特性,讨论了施主掺杂BaTiO3基PTC陶瓷缺陷行为与晶界势垒及其导电机理,解释了冷却速率和再氧化时间对样品的电性能以及PTC效应的影响.     

钛酸钡半导体陶瓷的显微结构分析

BaTiO_3半导体陶瓷广泛用做PTC热敏电阻和晶界层电容器。BaTiO_3半导体陶瓷是多晶材料,其性能不仅决定于化学组成,而且与其显微结构有着密切关系。BaTiO_3半导体陶瓷的电阻正温度系数效应(PTC效应)最先由W.Heywang提出的晶界势垒模型进行了解释。随后,又有一些作者对Heywang提出的晶界势垒模型进行了修正。为了能从直接的实验数据验证势垒模型,很多人研究了BaTiO_3PTC陶瓷的显微结构。这些有关BaTiO_3陶瓷显微结构     

氮化硼改善BaTiO_3基高温热敏陶瓷耐压特性的研究

研究了掺杂BN对改善高温PTC热敏陶瓷耐压特性的影响。实验结果表明,BN的加入促进了产品在达到最大电阻后电阻的稳定性,大幅提高了PTC陶瓷的耐电压强度,同时降低了其烧成温度,弱化了保温时间对敏感陶瓷常温电阻率的影响,提高了PTC的性能。     

钙铜钛氧高介陶瓷的B位锌掺杂与性能

采用固相反应法制备出B位Zn2+掺杂的CaCu3Ti4O12陶瓷,探讨了其相结构、显微组织和电学性能。Zn2+掺杂后CaCu3Ti4O12陶瓷的介电常数为6 564,10kHz~1MHz频率稳定性好,介电损耗值小于0.4,电学性能的改善与Zn2+掺杂后导致晶粒尺寸增大和晶粒电阻减小有关。通过对CaCu3Ti4-xZnxO12-δ(x=0.03)陶瓷的变温介电频谱分析,得到其介电弛豫晶界热激活能为0.529eV。     

Ni/陶瓷复合PTC材料的研究

探讨了Ni/陶瓷复合PTC材料的机理.通过引入GEM方程,分析相关的数学模型和实验数据,得出了:复合材料中,金属与陶瓷的电阻混合方式为近似的混联模式,电阻率符合如下公式:ρcomposite=(Vmetal×ρmetal+(1-Vmetal)×ρnceremica)-1/n.通过分析该公式,提出了提高复合材料性能的有效途径,为相关的研究提供了理论指导.     

在还原气氛烧结过程中施主掺杂量对(Bam-xSmx)TiO3基热敏材料PTC特性的影响

正温度系数(PTC)热敏陶瓷常用于低压集成电路的过流保护,为了适应市场对该样品低阻化的要求,人们一般采用还原再氧化的烧结工艺来制备片式PTC热敏陶瓷.本文主要研究了(Bam-xSmx) TiO3 (BST)基陶瓷在还原气氛中1300℃烧结30 min并在850℃再氧化热处理后其化学计量比和施主掺杂浓度对该样品的电性能及其PTC效应的影响.结果表明,BST基陶瓷样品的化学计量比和施主掺杂量都对该样品的电性能和PTC效应产生影响.随着施主掺杂含量的增加(0.2～0.5mol％ Sm3+)不同化学计量比样品的室温电阻率均呈现出先减小后增加的变化趋势,其中Ba过量样品的室温电阻率比Ti过量的和满足化学计量比样品的一般要高一些.m=1且施主掺杂0.3mol％ Sm3+的BST基陶瓷可以获得较好的PTC效应,它的室温电阻率(ρRT)和升阻比Lg(ρmax/ρmin)分别为383.1Ω·cm和3.1个数量级.此外,化学计量比和施主掺杂量对样品的平均晶粒尺寸有较大的影响,再氧化热处理对施主掺杂BST基PTC陶瓷的电性能以及PTC特性也有明显影响.     

高温大功率PTC材料研制

本文通过多元施主掺杂，以及添加CaCO3、增加耐压等方法，使（Ba－Ph）TiO3系PTC高温材料的PTC效应、大功率特性得以改善，并通过制备工艺的改进制出了居里温度240～360℃，功率密度达100W／cm2的高温大功率材料。     

Effect of Al2O3 on the microstructure and electrical properties of WO3-based varistor ceramics

The influence of Al₂O₃ additive on the electrical properties and microstructure of (Na,Mn)-doped WO₃ ceramics was studied. Addition of Al₂O₃ shifts the current–voltage characteristics to higher fields and inhibits the grain growth of the WO₃-based non-Ohmic ceramics. The non-linearity coefficient of the current–voltage characteristics of the Al₂O₃-doped WO₃ ceramics increases with sintering temperature and attains a maximum value at 1250°C.     

Sb2O3掺杂对ZnO压敏陶瓷晶界特性和电性能的影响

制备了掺有Sb2O3不同掺杂量ZnO压敏陶瓷样品,采用扫描电镜对样品进行显微结构分析,研究了Sb2O3掺杂浓度对ZnO压缩电阻显微结构和性能的影响,测量了样品的电性能,由样品C－V特性的测量计算出晶界参数,并由此讨论了陶瓷性能与晶界特性的相关性。研究发现,在ZnO压敏陶瓷样品中掺杂适量的Sb2O3可以提高ZnO压敏陶瓷样品的非线性性能,但当Sb2O3的摩尔分数超过0．088％时,电性能反而优化,这是因为Sb2O3掺杂浓度不同会引起晶界势垒高度、施主浓度与陷阱密度的变化,因此Sb2O3掺杂量要控制在适当的范围内。     

液相烧结SiC陶瓷

采用Al2O3、Y2O3为助烧剂,热压烧结获得了致密的α-SiC和β-SiC陶瓷,研究了起始粉末的性能对烧结体的物相组成和显微结构的影响。实验结果表明,Al2O3、Y2O3原位形成了YAG,材料以液相烧结机制致密化,并通过溶解和再析出机制,促进晶体生长。物相分析表明,β-SiC陶瓷粉末在烧结过程中发生了β→α的相变。显微结构观察显示,β-SiC陶瓷中生成了长柱状晶粒。     

大功率收发兼备压电陶瓷材料的制备与性能研究

采用传统固相烧结法制备Pb0.94Sr0.06（Zr0.53Ti0.47）O3＋（Ni2O3＋Cr2O3）0.1wt%＋xwt%MnO2＋ywt%CeO2（简称PCrNi-4）压电陶瓷,通过正交试验设计研究了MnO2掺杂、CeO2掺杂、烧结温度等因素对基体材料性能的影响。利用XRD和SEM,并结合常规电性能测试手段研究不同影响因素对材料相结构、微观结构以及压电介电性能的影响。结果表明,当w（MnO2）=0.1%,w（CeO2）=0.3%,烧结温度为1280℃时制备的陶瓷综合性能最佳,此条件下的试样各性能参数分别为：d33=304.8pC/N,Kp=0.6113,εT33=1520,tgδ=0.289%,d33×g33=61.12×10-12CVm/N,适合制备大功率收发兼备压电换能器。     

Improvement of response characteristics of TiO2 humidity sensors by simultaneous addition of Li2O and V2O5

Porous TiO₂ ceramics were prepared by adding various amounts of Li₂O and V₂O₅ and the humidity sensitivity of the resulting ceramics was investigated by means of electrical measurements, scanning electron microscopy and mercury intrusion porosimetry. Simultaneous addition of Li₂O and V₂O₅ to TiO₂ enabled sintering at temperatures as low as 700 °C and also decreased the impedance of the ceramics. Furthermore, in the ceramics including these additives simultaneously, excellent humidity sensitivity as well as good response characteristics were observed. The microstructures of these ceramics depended on the firing temperature and the amount and ratio of Li₂O/V₂O₅, and optimum humidity sensitivity was observed for the sample including both 0.25 mol% Li₂O and 0.75 mol% V₂O₅ fired at 700 °C. These results indicated that the humidity sensitivity and its response characteristics were closely related to the microstructure, and that improving the uniformity of microstructure is important for improving humidity sensitivity and its response characteristics.     

三维打印制备MAX基复相陶瓷研究进展

本文综述了三维打印(Three-Dimensional Printing,3DP)结合反应熔体渗透(Reactive Melt Infiltration,RMI)技术制备MAX基复相陶瓷的研究进展。在致密MAX基复相陶瓷的制备过程中,3DP技术的作用主要体现在两方面:一方面是实现预制体的成型,另一方面是通过孔隙结构和成分的设计控制所制备材料的微结构。3DP所制备的预制体呈现为典型的双孔径分布模式,有利于RMI的进行。通过3DP同RMI结合能够实现致密MAX基复相陶瓷的近尺寸成型,同时通过对初始原料、渗透熔体以及渗透温度等参数的优化能够实现微结构、力学性能以及电磁屏蔽性能的调控。     

Charge trapping characteristics of alumina based ceramics

The space charge dynamics is very important for electrical breakdown of alumina based ceramics. In this paper, the charge trapping/detrapping characteristics of alumina based ceramics were studied by means of isothermal surface potential decay (ISPD) method. For alumina and zirconia toughened alumina (ZTA) ceramic samples, the ISPD curves charged by corona discharge as well as microstructure characterization were carried out. For the first time, crossover phenomenon and hollow shaped potential profile were observed and reported in alumina based ceramics, indicating a surface potential decay process dominated by charge injection and volume conduction affected by the trap states in materials. In addition, the comparative trapping characteristics were evaluated based on a charge detrapping controlled decay model. The correlation between trap distribution and microstructure of alumina based ceramics was investigated. It was proposed that different charge trapping characteristics of alumina based ceramic samples was caused by varied shallow trap density of grain boundary.     

物理悬浮破碎与化学插层溶胶-凝胶相结合制备纳米ZrO_2结构陶瓷涂层研究

采用物理悬浮破碎与化学插层溶胶-凝胶相结合的方法,通过低温成膜制备出纳米ZrO2结构陶瓷涂层。利用扫描电镜(SEM)和X射线衍射试验(XRD)方法表征了陶瓷涂层的微观结构和晶形。通过热震、耐磨蚀测试、附着力和硬度检测手段,检测其成膜的宏观性能。结果表明,低温成膜的结构陶瓷热震性能够承受800℃的温度,而纳米ZrO2大部分为四方相,陶瓷涂层有较好的致密度,涂层与基材结合良好,抛光后断面涂层厚度20μm左右,耐磨蚀能力超过普通陶瓷涂层,附着力达到0级,硬度为9H,具有很好的实用性。     

Cr2O3掺杂Pb(Mn1/3Sb2/3)0.05Zr0.47Ti0.48O3压电陶瓷的性质

探讨了Cr2O3掺杂对锑锰锆钛酸铅Pb（Mn1/3Sb2/3）0.05Zr0.47Ti0.48O3（简称PMSZT）压电陶瓷性能影响.通过X射线衍射,电子顺磁共振以及扫描电镜分析了PMSZT＋z Cr2O3（z=0.2%～0.8%,质量分数）陶瓷的相组成,元素价态以及显微结构.结果表明：合成温度900℃保温2 h后,可以得到钙钛矿结构.随着Cr2O3掺杂量的增大,四方相的含量减少,准同相界向三方相移动.掺杂Cr2O3的质量分数为0.6%时：相对介电常数εr=1 650,介电损耗tanδ=0.006,压电常数d33=328 pC/N,机电耦合系数Kp=0.63,机械品质因数Qm=2 300,电性能优于Cr2O3掺杂量为0.2%,0.4%,0.8%的样品,但比未掺杂时的稍差.随着Cr2O3掺杂量的增加,PMSZT陶瓷的Curie温度降低,谐振频率变化率随温度变化由正变负.     

Microstructural and Chemical Influences of Silicate Grain-Boundary Phases in Yttria-Stabilized Zirconia

The microstructure and chemistry of grain-boundary phases in silicate-doped Y₂O₃─ZrO₂ ceramics were evaluated by analytical electron microscopy. Two different silicate compositions were used: one an aluminosilicate and the other a borosilicate glass. These grain-boundary phases had a significant impact on the grain morphology, the chemical composition of the grains, and the crystallization of second phases. These results indicate that controlled additions of specific glass phases may provide a means for tailoring the microstructure and physical properties of zirconia ceramics.