Moisture effect on the dielectric and structure of BaTiO3-based devices

Moisture effect on the dielectric behavior and structure of BaTiO₃-based devices were studied systematically. The dielectric measurement mainly concerned the capacitance and loss of specimen as a function of frequency and temperature between −10 and 50 °C in different measuring environments (vacuum, ambient air with and without dryer). A broad peak of capacitance and loss due to the moisture absorption, depending on frequency and temperature rate and corresponding to a dynamic process involving water absorption and de-absorption, was observed in the heating run when the measurement was carried out in ambient air without dryer. It showed that water absorption would change the apparent dielectric properties of devices and a heat treatment at 50 °C for the BaTiO₃-based devices was suggested to reduce the moisture absorption effect.     

碳酸锰和纳米钛酸钡的添加对钛酸钡陶瓷的影响

以钛酸丁酯和乙酸钡为起始原料,采用液相法制备了纳米钛酸钡。研究了纳米钛酸钡和碳酸锰的掺杂对普通亚微米级钛酸钡的形貌及介电性能的影响。结果表明,在普通钛酸钡中加入一定量的纳米钛酸钡可以促进晶粒的生长,同时提高陶瓷的介电常数。而在普通钛酸钡中加入一定量的碳酸锰则可以抑制晶粒的生长。但同时添加碳酸锰和纳米钛酸钡,碳酸锰对晶粒生长的抑制作用将居于主导地位,并且此时钛酸钡陶瓷的介电常数温度特性曲线与单独添加锰离子时的走势基本相同,室温附近的介电常数峰将由于钛酸钡陶瓷的细晶效应而弥散。     

BaTiO_3基无铅PTC热敏电阻材料的制备与研究

利用传统陶瓷工艺制备了掺杂(Bi0.5Na0.5)TiO3(BNT),CaCO3和Mn(NO3)2的钛酸钡基无铅PTC陶瓷材料(Bi0.5Na0.5)xBa1–xTiO3-yCaCO3-0.000 2Mn(NO3)2(x=0.005,0.020,0.040,0.080;y=0,0.02,0.04,0.06,0.08),研究了BNT和CaCO3的掺杂量对所制陶瓷微观结构和导电特性的影响。结果表明:试样的晶格常数比c/a、居里温度tC以及室温电阻率ρ25均随着BNT掺杂量的增加而增大;CaCO3的加入能有效降低样品的室温电阻率。当x=0.080,y=0.06时所制得材料的性能最好,其室温电阻率为7×102.cm,居里温度高于150℃,升阻比(ρmax/ρmin)达到103。     

Zr与稀土Nd复合掺杂对钛酸钡陶瓷结构及介电性能的影响

在1 270℃的烧结温度下,采用固相反应法对BaTiO3粉体进行Nd2O3和ZrO2双施主复合掺杂,合成(Ba0.98Nd0.02)(Ti1–xZrx)O3(BTNZ)陶瓷,研究了Zr掺杂量对BTNZ陶瓷的显微结构及介电性能的影响。结果表明:随着Zr掺杂量的增加,BTNZ陶瓷的介电峰移向室温;加入适量的Zr离子替代BaTiO3中的Ti离子能很好地改善BTNZ陶瓷的介电性能,当Zr掺杂量为x=0.01时,BTNZ陶瓷的相对介电常数可达7 200。     

喷雾造粒粉体对BaTiO3系PTCR半导体陶瓷性能的研究

研究了通过喷雾造粒制得的BaTiO3系PTCR热敏陶瓷粉体性能对生坯成型及瓷体物理、PTC效应、电学等性能的影响,与手工造粒粉体比较,由于喷雾造粒的粉体流动性好,表面活性大,粒度均匀,其成型性及烧结后瓷体PTcR效应、电学性能均有明显提高.     

Low temperature sintering properties of Y-doped BaTiO3 ceramics by BaB2O4 sintering aid

The sintering process of semiconducting Y-doped BaTiO₃ ceramics added with BaB₂O₄ as low temperature sintering aid were investigated. When the low temperature sintering aid BaB₂O₄ added Y-doped BaTiO₃ ceramics prepared by Sol-Gel method, the sintering temperature of BaTiO₃-based ceramics would be greatly decreased, and also widen sintering range. Y-doped BaTiO₃ ceramics with BaB₂O₄ addition can be obtained at 1050 °C. Ceramics samples with room temperature resistivity 60-80 Ω cm, ratio of the maximum resistivity to minimum resistance (Rmax/Rmin) 10⁴ and temperature coefficient of resistivity (α) 10%/°C were obtained.     

The synthesis and dielectric study of BaTiO3/polyimide nanocomposite films

Polymer-ceramic dielectric composites have been of great interest because they combine the processability of polymers with the desired dielectric properties of the ceramics. A novel, simple method to make thin, homogeneous composite films with varying amounts of ceramic filler content has been proposed. Nanocomposite thick films of barium titanate (BaTiO₃) in polyimide (PI) from 3,3′,4,4′-benzophenone tetra carboxylic dianhydride, 4,4′-oxy dianiline have been successfully prepared by in situ imidization using n-methyl pyrrolidinone as the solvent. The dielectric properties of the nanocomposite films were discussed for various filler volume contents. These nanocomposite films exhibited stable dielectric properties in the various frequency ranges. Films were characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The curing cycle was optimized using FTIR. XRD results confirm BaTiO₃ particles remain unchanged in the PI matrix and no undesired secondary phases are present in the films. Their glass transition behavior and thermal stability were investigated by DSC and TGA, and the films were stable to 300 °C. Scanning electron microscope images show that the BaTiO₃ phase is well dispersed in the polymer matrix.     

MgTiO_3掺杂对BST基电容器陶瓷介电性能的影响

采用固相法制备了MgTiO3掺杂的(Ba0.65Sr0.35)TiO3(BST)陶瓷,研究了MgTiO3掺杂量对(Ba0.65Sr0.35)TiO3(BST)基电容器陶瓷介电性能和微观结构的影响。结果表明:随着MgTiO3掺杂量的增加,BST陶瓷的介电常数(εr)、介质损耗(tanδ)和耐压强度(Eb)均先增大后减小。当MgTiO3掺杂量为质量分数0.8%时,BST陶瓷的综合介电性能较好:εr为4350,tanδ为0.0055,Eb为5.7×103V/mm(AC),容温特性符合Y5U特性。     

Li过量对M-相固溶体Li2O-Nb2O5-TiO2陶瓷微波介电性能的影响

含有M-相固溶体Li2O-Nb2O5-TiO2(LNT)的微波介质陶瓷具有烧结温度(约1100℃)低,介电常数ε(r)65～70)及Q·f值(约5000 GHz)高的特点,但其频率温度系数τf却往往偏高(约23×10-6/℃).为此,系统研究了非化学计量比下Li含量对LNT陶瓷微波介电性能的影响.实验结果表明,Li含量增加能有效调节LNT陶瓷的频率温度系数至近零而不影响其他性能.当Li含量过量5％(质量分数)时,LNT陶瓷具有最佳性能:ε(r)=69.73,Q·厂=5 543GHz(f=3.518 GHz),τf=-4.4×10-6℃.     

ZnO-B_2O_3玻璃对Mg_2TiO_4微波介质陶瓷结构和性能的影响

利用传统固相烧结法制备了ZnO-B2O3玻璃掺杂的Mg2TiO4微波介质陶瓷,研究了ZnO-B2O3玻璃掺杂对所制陶瓷相成分、微观形貌和微波介电性能的影响。结果表明:ZnO-B2O3玻璃掺杂能使Mg2TiO4陶瓷的致密化温度降低200℃左右。当Mg2TiO4中掺杂质量分数2%的ZnO-B2O3玻璃时,经1 300℃烧结所得陶瓷微波性能较好:εr=13.62、Q.f=101 275 GHz、τf=–51×10–6/℃。     

Zn-Zr共掺对0.95MgTiO_3-0.05CaTiO_3陶瓷介电性能的影响

采用固相反应法制备了(Mg0.93Ca0.05Zn0.02)(Ti1-xZrx)O3介质陶瓷。研究了Zn-Zr共掺杂对0.95MgTiO3-0.05CaTiO3(95MCT)陶瓷介电性能的影响。结果表明:Zn-Zr共掺杂能有效降低95MCT陶瓷的烧结温度至1 300℃,改善介电性能,并对介电常数温度系数αc具有调节作用。当Zn2+和Zr4+掺杂量均为摩尔分数0.02时,在1 300℃烧结2.5 h获得的95MCT陶瓷具有最佳介电性能:εr=22.02,tanδ=2.78×10-4,αc=2.98×10-6/℃。     

Li2ZnTi3O8微波介质陶瓷烧结工艺的研究

采用传统固相反应法制得Li2ZnTi3O8微波介质陶瓷,研究了主要烧结工艺参数对所制陶瓷的物相组成、显微组织及微波介电性能的影响.结果表明:经900℃预烧并在1 075℃保温4h所得陶瓷试样只含有单一的Li2ZnTi3O8相;另外,其显微组织均匀,气孔等缺陷较少,相对密度达到98.5％,且具有良好的介电性能:ε(r)=26.6,Q·f=75 563 GHz,τf=-12.4×10-6/℃.     

BaSnO3/BaBiO3复相陶瓷的显微结构及电性能

以BaCO3、SnO2和Bi2O3为原料,采用传统固相反应法制备了具有NTC特性的BaSnO3/BaBiO3复相陶瓷。借助XRD、SEM和R-t特性测试仪,研究了该陶瓷的相结构、断面形貌及n(BaBiO3)对其电性能的影响。结果表明:随着r(BaBiO3∶BaSnO3)从0.1∶1.0增大到0.9∶1.0,样品的B25/85值从4400K降低到3000K,同时室温电阻率ρ25从106Ω·cm降低到103Ω·cm。     

MBi_4Ti_4O_(15)基陶瓷的研究现状与发展趋势

铋层状结构无铅铁电陶瓷具有良好的抗疲劳性能和较高的居里温度,在铁电存储以及高温压电器件方面具有广阔的应用前景。介绍了MBi4Ti4O15基铋层状陶瓷的结构特点,综述了微量元素掺杂、粉体制备方法和晶粒定向技术对该陶瓷铁电压电性能的影响。并展望了MBi4Ti4O15基铋层状无铅铁电陶瓷未来的发展趋势。     

Piezowiderstandseffekt in BaTiO3-Halbleitern

BaTiO₃ semiconductors show a strong dependence on pressure of the electrical resistance. The impedance behaviour reveals this piezo resistance effect to be mainly localized in the grain boundary barriers which are also responsible for the anomalous increase of the resistance above the Curie temperature. The dependence of the resistance on both the temperature and the stress near the Curie point may be explained by the height of the potential barriers which is ferroelectrically controlled.

Résumé

Les semiconducteurs en TiO₃Ba démontrent une forte dépendance da la résistance électrique en fonction de la pression. Le comportement de l'impédance démontre que cet effet piézo-résistif est surtout localisé dans les barrières de reobrds de grain qui sont aussi responsables de l'augmentation anormale de la résistance au-dessus de la température Curie. La dépendance de la résistance en fonction de la température et de l'effort près du point Curie peut être expliquée par la hauteur des barrières de potentiel qui est contrôlée ferroélectriquement.     

Magnetic properties of Co- and Mn-implanted BaTiO3, SrTiO3 and KTaO3

Implantation of Co or Mn into single-crystal BaTiO₃(K), SrTiO₃ or KTaO₃(Ca), followed by annealing at 700 °C, produced ferromagnetic behavior over a broad range of transition metal concentrations. For BaTiO₃, both Co and Mn implantation produced magnetic ordering temperatures near 300 K with coercivities 70 Oe. The M–T plots showed either a near-linear decrease of magnetization with increasing temperature for Co and a non-Brillouin shaped curve for Mn. No secondary phases were detected by high-resolution X-ray diffraction. The same basic trends were observed for both SrTiO₃ and KTaO₃, with the exception that at high Mn concentrations (5 at.%) the SrTiO₃ was no longer ferromagnetic. Our results are consistent with recent reports of room temperature ferromagnetism in other perovskite systems (e.g. LaBaMnO₃) and theoretical predictions for transition metal doping of BaTiO₃ [Nakayama et al., Jap. J. Appl. Phys. 40 (2001) L1355].     

Charge transport in thick SiO2-based dielectric layers

Charge transport in thick (≥ 1 μm) SiO₂-based dielectric layers was investigated by means of I(U) measurements. Investigations were carried out on thermally grown field oxide (FOX) as well as on TEOS and BPSG. Gate oxide layers (GOX) were measured as reference. C(U) measurements were performed for the determination of charges in the oxide. To determine the electrical parameters of the layers, the model from Chen and Wu[1] was developed further. The model takes into account tunnelling, capture and emission processes, impact ionization, recombination, interface states and ohmic currents.

The I(U) characteristics for all dielectrics examined can be described with the aid of the model. The FOX parameters correspond to those of GOX. The parameters of TEOS and BPSG fluctuate strongly with the process parameters. After high-temperature annealing and from measurement of the examined parameters, the insulation properties of TEOS and BPSG were found to be at least as good as those of FOX.     

Current-voltage characteristics and capacitance of single grain boundaries in semiconducting BaTiO3 ceramics

Specimens were prepared of doped ceramic barium titanate in the form of bars which, between their metallized ends, contained only one high-resistance grain boundary running across the entire cross-section. The measurements covered the differential capacitance of these individual grain boundaries, under bias, and their d.c. current-voltage characteristics. The results can be described quite well by a model in which a layer of a second phase present between the barium titanate grains is assumed to possess, firstly, acceptor character and, secondly, a dependence of its permittivity on the temperature and the electric field strength.     

Zn位非化学计量对BaNb0.69(Zn0.116Co0.217)O3微波介电性能的影响

采用传统固相反应法制备BaNb0.69[Zn0.116(1+0.025x)CO0.217]O3(BCZN)(x=0～4)微波介质陶瓷.研究了Zn位离子的微量添加对BCZN陶瓷性能的影响.结果表明:少量添加Zn,可以促进烧结致密化,改善BCZN陶瓷的介电性能.在1 300℃下烧结3h,可以获得τf近零,介电常数ε(r)为33、Q·f为51 322 GHz的陶瓷.