低电阻率Ba0.92Ca0.08Ti1.02O3PTCR陶瓷界面缺陷态研究

用TEM和EDS相结合的测试手段,研究了低电阻率Ba_0.92Ca_0.08Ti_1.02O₃PTCR陶瓷材料的界面元素分布.根据界面元素分布的情况,对低电阻率Ba_0.92Ca_0.08Ti_1.02O₃PTCR陶瓷界面可能存在的缺陷态进行分析,认为在低电阻率Ba_0.92Ca_0.08Ti_1.02O₃PTCR陶瓷界面上主要存在以下缺陷结构:Mn"_Ti,Mn’_Ti或Al’_Ti,V"_Ba.     

BaTiO3基PTCR陶瓷中B2O3蒸汽掺杂的异常行为

钛酸钡基半导化陶瓷中的PTCR效应通常与材料中的施受主掺杂密切相关。在高温下B2O3具有较高的蒸汽压,通过B2O3蒸汽掺杂的研究表明,含主族元素B的氧化物蒸汽掺杂,钛酸钡基半导化陶瓷样品的升阻比同样得到了大幅度提高,同时室温电阻率也有所增加。B2O3蒸汽掺杂BaTiO3基材料的PTCR效应的提升可能得益于硼填隙和钡缺位相关的复合缺陷在晶界上的形成。     

Ba0.85Ca0.15Zr0.1Ti0.9O3/CoFe2O4叠层复合陶瓷的制备与磁电耦合效应研究

以CoFe2O4压磁体、掺CuO和CeO2助烧剂的压电体Ba0.85Ca0.15Zr0.1Ti0.9O3为基本叠层材料,采用界面固相熔融渗透法制备了掺助烧剂Ba0.85Ca0.15Zr0.1Ti0.9O3-CoFe2O4叠层复合陶瓷。叠层复合陶瓷的压电压磁相叠层界面结合良好。随着压磁相与压电相厚度比比率的增加,叠层复合陶瓷的饱和磁致伸缩系数–λ从67×10-6增加到134×10-6、压电系数d33从340 pC/N逐渐减小到205 pC/N;磁电耦合系数先增大后减小,在厚度比为2、外磁场为100 mT时得到最大值3200 mV/(cm.mT)。     

YCl3取代Y2O3降低BaTiO3基PTCR陶瓷电阻率机理研究

采用YCl3溶液作为施主掺杂剂,在空气中烧结制备一系列BaTiO3陶瓷样品,对其室温电阻率及PTC效应进行研究.同时与Y2O3和YNO3溶液掺杂的样品对比,借助XRD、XRF等分析手段,研究了YCl3溶液掺杂降低BaTiO3基PTCR陶瓷室温电阻率的机理.研究结果表明,经空气中高温烧结后,样品中仍残留部分Cl元素,能取代O位起施主作用,烧结时Cl的挥发过程也能导致样品室温电阻率的降低,最后,施主掺杂剂以溶液的形式加入,能使其在粉料中分布均匀,有助于半导化.     

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．     

电场对(Ba0.97Ca0.03)(Ti0.82Zr0.18)O3无铅压电陶瓷铁电性的影响

采用溶胶-凝胶方法制备了(Ba0.97Ca0.03)(Ti0.82Zr0.18)O3无铅压电陶瓷。在电场1～8kV/cm下,频率为0.01～10Hz范围内,对其电滞回线进行了分析。实验结果表明(Ba0.97Ca0.03)(Ti0.82Zr0.18)O3陶瓷的电滞回线随电场值和频率的变化明显,在低电场下,随着频率的增加矫顽场(Ec)单调减小,在低频下剩余极化(Pr)增加;而在高电场下,随着频率的增加Ec单调增大,电滞回线达到饱和时,电滞回线随不同测试频率无明显变化。     

Ba0.8Sr0.2Ti0.5Mn0.5O3纳米晶体的合成及气敏性质研究

采用复合碱媒介法(CHM),在合成BaMnO3和Ba0.5Sr0.5MnO3的基础上,以Sr(NO3)2、BaCO3以及MnO2和TiO2为原料,在200℃、24h的生长条件下,用20%的Sr离子替代20%的Ba离子,用50%的Ti离子替代50%的Mn离子成功合成了Ba0.8Sr0.2Ti0.5Mn0.5O3纳米晶体。采用XRD、SEM及EDS对产物的晶相、形貌和成分进行了分析,对Ba0.8Sr0.2Ti0.5Mn0.5O3制作的电极进行了气敏性质的测定。     

Ba置换改性(Ca1-xBax)[(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷结构与微波介电性能的研究

研究了Ba置换改性对Ca [(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷微观结构与介电性能的影响.通过XRD与SEM分析发现,当x=0.15,(Ca1-xBax) [(Mg1/3Nb2/3)0.6Ti0.4]O3形成了正交晶系钙钛矿结构的单相固溶体;当x=0.20～0.80时,改性陶瓷为正交与六方钙钛矿结构的两相复合固溶体;当x=0.85 时,所形成(Ca0.15Ba0.85) [(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷为六方钙钛矿结构的单相固溶体.(Ca1-xBax) [(Mg1/3Nb2/3)0.6Ti0.4]O3系陶瓷微波介电性能的变化与Ba在材料内部的分布状态密切相关,与基材CMNT陶瓷相比:当x=0.15时,陶瓷的介电常数提高,介电损耗降低,谐振频率温度系数向负方向移动:εr=55,Qf值=32000GHz(6.5GHz下),τf=-36.82ppm/℃;当x=0.20～0.80间变化时,(Ca1-xBax)[(Mg1/3Nb2/3)0.6Ti0.4]O3两相复合陶瓷的微波介电性能由于复合效应而表现出连续变化的规律:εr= 45～33 ,Qf值= 30500～40200GHz(6.3GHz～7.6GHz下),τf = -17.7～12.52ppm/℃;当x=0.85时,单相钙钛矿固溶体(Ca0.15Ba0.85) [(Mg1/3Nb2/3)0.6Ti0.4]O3获得良好的微波介电性能:εr=31,Qf值达到44000GHz(8.5GHz下),τf=10.81ppm/℃.     

Sr0.4Pb0.6TiO3基陶瓷晶界组成对热敏特性的影响

采用固相烧结工艺制备出了Sr0.4Pb0.6TiO3半导体陶瓷元件，其阻温特性具有独特的NTCR和PTCR复合效应，陶瓷室温电阻率及居里点以下的NTCR效应随着烧结温度的升高而提高，适当过量PbO则能降低陶瓷室温电阻率及其NTCR效应。利用XRD，SEM和EDS分别对样品的相结构，形貌及成份分布等进行分析。结果显示晶界中的Sr,Ti含量相对较高，而Pb含量相对较低，材料的阻温特性明显受其影响，铅挥发造成的阳离子空位是该类半导体陶瓷在居里点下出现NTCR效应的主要原因之一，同时探讨Y^3 离子掺杂（Sr,Pb)TiO3陶瓷的半导体机理和热敏特性。     

Nb或La掺杂的Ba(Ti0.9Sn0.1)O3基陶瓷的介电性能

研究了掺杂Nb2O5或La2O3的Ba(Ti0.9Sn0.1)O3基陶瓷的介电性能.结果表明掺入0.5%(摩尔比)Nb或La后Ba(Ti0.9Sn0.1)O3基陶瓷的居里温度向低温方向明显移动,而且介电常数显著增大,室温介电常数达30000,峰值介电常数达35000左右,同时介电损耗也明显增加.     

Effect of atmosphere on the PTCR characteristics of porous Ba(Ti,Sb)O3 ceramics produced by adding corn-starch

Porous Ba(Ti,Sb)O₃ ceramics were fabricated by adding corn-starch at 20 wt %. The effect of atmosphere on the PTCR characteristics of the porous Ba(Ti,Sb)O₃ ceramics and the role of oxygen on the grain boundaries in the PTCR characteristics of the Ba(Ti,Sb)O₃ ceramics were investigated. In air, O₂, N₂, and H₂ atmospheres, the electrical resistivity of Ba(Ti,Sb)O₃ ceramics below 150 °C was independent of atmosphere, while it was strongly dependent on atmosphere above 200 °C. The low electrical resistivity in reducing atmospheres was due to a decrease in potential barrier height, which originated from an increase in the number of electrons owing to the desorption of chemisorbed oxygen atoms at the grain boundaries. In a N₂ atmosphere, the electrical resistivity of Ba(Ti,Sb)O₃ ceramics during the cooling cycle was lower than that during the heating cycle, and then the electrical resistivity of the porous Ba(Ti,Sb)O₃ ceramics during subsequent heating and cooling cycles was increased again by exposure to an O₂ atmosphere.     

TiCl3-doped Ba0.92Ca0.08TiO3 PTCR ceramics with low r.t. resistivity

The influence of TiCl₃ solution on the room temperature (r.t.) resistivity and electrical properties of Ba_0.92Ca_0.08TiO₃ PTCR ceramics was studied. The results indicate that the PTC effect can be improved significantly when an appropriate amount of TiCl₃ in solution is added to the original materials. Some of the doped Ti³⁺ ions segregate at grain boundaries behaving as acceptors by substituting for Ti site or valence varying (from Ti³⁺ to Ti⁴⁺). As a result, the surface charge density N _s) increases and the barrier height at grain boundaries () is enhanced.     

掺钇(Ba,Ca)(Ti,Zr)O_3电容器陶瓷抗还原性的研究

对掺钇的(Ba,Ca)(Ti,Zr)O3(BCTZ)电容器陶瓷进行了抗还原性研究,研究了不同摩尔分数的钇的掺杂对BCTZ电容器陶瓷的介电性能、显微结构和密度的影响。结果表明,随着Y2O3掺杂量的增加,BCTZ陶瓷的室温介电常数、介质损耗逐渐减小,居里温度向低温方向移动,同时绝缘电阻率升高,BCTZ陶瓷抗还原性能提高;Y2O3的掺入能够促进BCTZ陶瓷的致密化,并有利于抑制BCTZ陶瓷的晶粒生长。     

热压烧结增强Ca3Co4O9多晶的c轴择优织构和电输运性质的研究

分别采用常压固相反应和进一步的真空热压烧结法制备了Ca_3Co_4O_9多晶块材,通过XRD、SEM、致密度、电阻率-温度曲线、霍尔效应测试,对比研究了热压烧结对多晶织构和电输运性质的影响。结果表明两种方法制备的多晶样品均为c轴择优,经热压烧结后多晶的择优织构显著增强,致密度增大,但真空烧结使样品中氧的化学计量比不足,结晶质量略有下降。热压烧结后多晶的面内电阻率显著下降,其室温电阻率约为常压烧结样品的1/7,且电阻率随温度的降低而增大,这主要是由于热压样品晶粒沿(00l)择优排列显著增强,使沿材料ab面内的电输运占优,且晶界和缺陷散射减弱使Co~(4+)载流子迁移率增大。     

Sm2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Sm2O3掺杂的(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(BCZT)无铅压电陶瓷.借助XRD、SEM等手段对该陶瓷的显微结构与电性能进行了研究.结果表明,Sm2O3的掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度点Tc从85℃提高到95℃.当Sm2O3掺杂量为0.02wt%～0.1wt%时,样品具有典型ABO3型钙钛矿结构.Sm2O3掺杂量为0.02wt%时,所得陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因子Qm、介电损耗tanδ和介电常数εr分别为590 pC/N、0.52、43、1.3%和3372.     

Sintering condition and PTCR characteristics of porous (Ba,Sr)(Ti,Sb)O3

We fabricated porous (Ba,Sr)(Ti,Sb)O₃ ceramics by adding potato-starch (1–20 wt %) and investigated the effects of sintering temperature (1300–1450 °C) and time (0.5–10 h) on the positive temperature coefficient of resistivity characteristics of the porous ceramics. The room-temperature electrical resistivity of the (Ba,Sr)(Ti,Sb)O₃ ceramics decreased with increasing sintering temperature, while that of the ceramics increased with increasing sintering time. For example, the room-temperature electrical resistivity of the (Ba,Sr)(Ti,Sb)O₃ ceramics for the samples sintered at 1300 °C and 1450 °C for 1 h is 6.8×10³ and 5.7×10² cm, respectively, while that of the ceramics is 6.5×10² and 1.3×10⁷ cm, respectively, for the samples sintered at 1350 °C for 0.5 h and 10 h. In order to investigate the reason for the decrease and increase of room-temperature electrical resistivity of the samples with increasing sintering temperature and time, the average grain size, porosity, donor concentration of grains (N _d), and electrical barrier height of grain boundaries () of the samples are discussed.     

(Ba1-xSrx)La4Ti4O15（x=0.8～0.95）陶瓷的微结构及微波介电性能研究

采用固相反应法制备了(Ba1-xSrx)La4Ti4O15(x=0.8~0.95)复合体系微波介质陶瓷,并对其进行物相组成、晶体结构分析以及微波介电性能的研究.研究结果表明,(Ba1-xSrx)La4Ti4O15陶瓷主晶相为SrLa4Ti4O15,并伴随有第二相SrLa8Ti9O15.SEM观察表明,Ba0.2Sr0.8La4Ti4O15陶瓷内部微观结构致密,晶粒尺寸在10~20μm之间,晶界清晰.随着x值逐渐增大,(Ba1-xSrx)La4Ti4O15陶瓷中晶粒形态发生变化,气孔增多.在x=0.8时,(Ba1-xSrx)La4Ti4O15陶瓷具有优良的微波介电性能,即εr=40.86,Q×f≈62806 GHz,τf=20×10 6/℃.随着Ba2+的含量逐渐增加,该陶瓷的介电常数εr单调上升,品质因子Q×f值增加,说明适量的Ba2+替代Sr2+能改善陶瓷的微波介电性能.     

Microstructures and Dielectric Properties of Ba1-xSrxTiO3 Ceramics Doped with B2O3-Li2O Glasses for LTCC Technology Applications

Ba1-xSrxTiO3 ceramics, doped with B2O3-Li2O glasses have been fabricated via a traditional ceramic process at a low sintering temperature of 900 ℃ using liquid-phase sintering aids. The microstructures and di- electric properties of B2O3-Li2O glasses doped Ba1-xSrxTiO3 ceramics have been investigated systemat- ically. The temperature dependence dielectric constant and loss reveals that B2O3-Li2O glasses doped Ba1-xSrxTiO3 ceramics have di?usion phase transformation characteristics. For 5 wt% B2O3-Li2O glasses doped Ba0.55Sr0.45TiO3 composites, the tunability is 15.4% under a dc-applied electric field of 30 kV/cm at 10 kHz; the dielectric loss can be controlled about 0.0025; and the Q value is 286. These composite ceramics sintered at low temperature with suitable dielectric constant, low dielectric loss, relatively high tunability and high Q value are promising candidates for multilayer low-temperature co-fired ceramics (LTCC) and potential microwave tunable devices applications.