添加Nd2O3对氧化锌压敏阀片电性能与显微组织的影响

研究了微量Nd2O3添加剂对氧化锌压敏阀片的压敏电位梯度、漏电流和压比的影响,并对其显微组织进行了分析研究,从理论上探讨了Nd2O3对氧化锌压敏阀片电性能与组织的作用机理。研究结果表明:当Nd2O3的摩尔分数为0.04％时,氧化锌压敏阀片的压敏电位梯度最高,漏电流最小,压比最低,具有优良的综合电性能。其原因是Nd2O3加入到氧化锌压敏阀片中,使晶粒尺寸减小所致。     

纳米氧化铋粉体的制备及对ZnO压敏电阻性能的影响

采用直流电弧等离子法可以制备出包含有a和β相,尺寸约为70 nm的纳米氧化铋粉体,收率可达30％。利用制备的纳米氧化铋粉体替代微米级材料制备氧化锌压敏陶瓷后,研究了其对器件电学性能和陶瓷微观结构的影响。实验发现:纳米氧化铋使用量为1.6％摩尔分数时其压敏电压梯度和通流值分别为185 V/mm和4 700 A/cm2,而达到相同值所需微米氧化铋用量则分别为1.9％和1.85％。可见,如采用纳米氧化铋替代微米氧化铋可以减少用量10％～20％,而达到相同的电性能。     

球磨时间对钛酸钡介电性能的影响

通过改变混料的秩序以及采用沉降、水煮损耗、温度特性、电导率和化学分析等测试手段，研究了制备钛酸钡的球磨工艺中球磨时间对钛酸钡粉体均匀性及钛酸钡介电性能的影响。研究结果表明：采用不同的球磨时间制得的钛酸钡性能差别较大，球磨时间达12小时时，能减少球磨引起的团聚，极大地改善了固相合成BaTiO3粉体均匀性，并最终提高了钛酸钡的介电性能。     

球磨工艺对钛酸钡陶瓷介电性能的影响

研究了固相法合成BaTjO3粉体时,在滚筒磨和搅拌磨中球磨BaCO3和TiO2粉体过程中,浆料的粒度、凝聚程度与球磨时间、筒容积的关系,分析了粉体均匀性对BaTiO3、陶瓷介电性能的影响.研究结果表明:TiO2粉体在球磨过程中,粒度大小没有显著变化,导致粉体凝聚的主要原因是BaCO3粉体;应先球磨BaCO3粉体10小时后再加入TjO2粉体继续球磨2小时所得的物料颗粒要比钡钛一起球磨所得的颗粒均匀,合成BaTiO3均匀性好;采用搅拌磨时,制备的BaTiO3陶瓷介电性能优于滚筒磨.     

水热合成钛酸锶粉体增强压敏电阻器电性能的研究

以硝酸锶Sr(NO3)2为锶源、酞酸四丁酯Ti(OC4H9)4为钛源,加入矿化剂NaOH/KOH,在130℃下反应24h水热合成了SrTiO3粉体。将水热粉体应用到压敏电阻器中,分别采用XRD、电性能测试、SEM等手段对产物进行表征。电性能测试结果显示,与传统固相法制备的SrTiO3压敏电阻器相比,同配方下此类压敏电阻器电性能获得显著提高,压敏电压V1mA和非线性系数ɑ分别达到120V和8。     

高能球磨时间对MgNb2O6陶瓷显微结构和微波介电性能的影响

采用高能球磨法制备粉体,研究了粉体球磨时间对MgNb2O6陶瓷显微结构和微波介电性能的影响,结果表明,1180℃烧结陶瓷,随球磨时间增加,平均粒径减小,气孔率降低,相对密度增大,介电常数增大;升高烧结温度到1220℃以上,不同球磨时间制备陶瓷样品相对密度达到95.8％以上,平均晶粒尺寸3.5m,εr为19.7,而Qxf值随球磨时间先增大后减小.高能球磨制备粉体能有效促进MgNb2O6陶瓷在1220℃下中温烧结,且具有优良的微波介电性能(εr=19.7,Q×f=28 744 GHz),有望成为新一代中温烧结高频微波介质基板材料.     

La2O3掺杂对Zn–Pr基压敏陶瓷电学特性的影响

利用固相烧结法制备出了ZnO–Pr₆O₁₁–Co₂O₃–Cr₂O₃–La₂O₃氧化锌压敏陶瓷。研究了La₂O₃掺杂对氧化锌压敏陶瓷微观结构、压敏特性以及介电性能等方面的影响。结果表明:在La₂O₃掺杂量为1.5%(摩尔分数)时,氧化锌压敏陶瓷的综合性能最好,其晶粒尺寸最小且较为均匀,击穿场强达到最高(752 V/mm),非线性系数较大(12),晶界电容达到最大(276 pF),介电损耗较小。     

Co2O3的理化性能对ZnO压敏陶瓷电性能的影响

本文详细研究了氧化钴的理化性能对ＺｎＯ压敏陶瓷性能的影响。论述了Ｃｏ２Ｏ３的热特性对压敏陶瓷烧成工艺产生的影响及控制措施，从理论上探讨了氧化 中所含杂质Ｆｅ、Ｃｕ，Ｎａ等对ＺｎＯ压敏陶瓷电性能的不利作用。提出了控制的上限，并试制出一种用于氧化锌压敏陶瓷的性能优良的Ｃｏ２Ｏ３粉体。     

粉体的球磨方式对Li1.0Nb0.6Ti0.5O3锂铌钛陶瓷烧结行为及微波介电性能的影响

通过X射线衍射、扫描电镜等分析手段结合介电性能测试结果,探讨了不同球磨方式(普通球磨及砂磨)制备的粉体对Li1.0Nb0.6Ti0.5O3(LNT)锂铌钛陶瓷的烧结行为、微观结构及微波介电性能的影响.用砂磨的方式粉碎粉体,获得了粒度分布均匀且分散性很好的粉体,在一定程度上降低了LNT陶瓷的烧结温度.另外,通过砂磨粉碎的粉体烧结而得到的陶瓷样品密度、相对介电常数(ετ)及机械品质因数与谐振频率的乘积(Q×f均高于普通球磨工艺制备的.结果表明:在1050℃烧结的陶瓷其具有相对优异的微波介电性能,ετ=9.9,Q×f=5 887 GHz,谐振频率温度系数τf=28.3×10-6/℃.     

氧化锌压敏陶瓷研究现状

本文论述了氧化锌压敏陶瓷的用途和发展趋势,以及压敏陶瓷的原理、配方和制备工艺,并着重讲述了纳米氧化锌压敏陶瓷粉末的制备。     

Effects of sizes of additive particles on suspensions,microstructures, and electrical properties of ZnO varistors

The effects of the sizes of the additives on the dispersion of the mixed suspensions, the microstructures, and the comprehensive electrical properties of the ZnO varistors were investigated. The particle size distribution, the viscosity, and the zeta potential of the suspension were characterized to evaluate the effect of the sizes of the additives on the dispersion of the metal oxide particles. The potential gradient, the leakage current, the nonlinear coefficient, the voltage ratio, and the aging coefficient were considered to estimate the effect of the sizes of the additives on the performance of the ZnO varistors. The electrical testing results showed that a proper amount of milling of the additive particles could improve the comprehensive electrical properties, while an excessive milling produced the opposite effect. When the milling time of the additive particles reached 30 minutes, the dispersion of ZnO-additive mixed suspension was the best. The as-prepared varistors showed the optimal electrical performance with potential gradient of 310 V/mm, leakage current of 1 μA, nonlinear coefficient of 32.7, voltage ratio of 1.69, and aging coefficient of 0.59.     

高能球磨对Pr_6O_(11)和Y_2O_3掺杂ZnO压敏电阻微观结构和电学性能的影响

利用高能球磨法制备Pr6O11、Y2O3掺杂ZnO压敏电阻,并对球磨时间对微观结构、物相组成及电学性能的影响进行了研究和分析。高能球磨有利于微观组织的均匀化和晶粒的细化,从而提高了电学性能。当球磨时间从0到10 h时,烧结后的ZnO晶粒尺寸变化从8.7到4.0μm,坯体烧结密度变化从5.40到5.62 g/cm3。最佳的制备工艺为球磨时间为7.5 h,烧结温度为1100℃,其对应的电学性能分别为:电位梯度(V1mA)是542 V/mm,漏电流(IL)是2.88μA,非线性系数(α)是47。     

High field ZnO varistors prepared by spark plasma sintering

Abstract

ZnO varistors with submicrometre and nanoscaled microstructures and enhanced electrical properties were prepared by spark plasma sintering (SPS). The densification, grain size and switch field of the varistors were compared with those of hot pressed material. The switching field increased with decreasing grain size, and very rapidly below 500 nm. Switching fields up to 180 kV cm^?1 were obtained for ceramics with submicrometre grain sizes (380 nm). This is nearly two orders of magnitude higher than those currently reported for commercial ZnO varistors. A nano powder, prepared by high energy milling, was sintered to a high density at much lower temperatures compared with the submicron powders and had a nanoscale grain size (45 nm). The nanoceramic broke down dielectrically under very high fields (>260 kV cm^?1) before a varistive response was apparent.     

Microstructural Morphology and Electrical Properties of Copper- and Niobium-Doped Tin Dioxide Polycrystalline Varistors

The influence of a Nb₂O₅ additive on the densification, microstructural morphology, and nonlinear electrical properties of the CuO-doped SnO₂-based varistors was investigated. It was found that copper oxide significantly improves the densification of the SnO₂ ceramics. The effects of Nb₂O₅ on tin dioxide varistors were analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and capacitance–voltage measurements, as well as impedance spectroscopy. Copper oxide segregates at the grain boundaries and precipitates at triple points, and niobium makes the tin dioxide grain semi-conductive. The copper oxide intergranular insulating layer separates two semi-conductive tin dioxide grains and forms the barriers. The reason for the nonlinearity of SnO₂-based ceramics was explained.     

Phase Identification and Electrical Properties in ZnO–Glass Varistors

Ceramic varistors based on ZnO with lead zinc borosilicate glass instead of Bi₂O₃ were prepared. The effect of sintering conditions on the electrical properties was studied by sintering samples at various temperatures and cooling them at different rates. The sample sintered at 1250°C for 1 h, then furnace cooled, possessed the best electrical properties, as characterized by the highest nonlinear coefficient, lowest leakage current, and lowest degradation. The microstructure and crystal structure of the glass phase of ZnO–glass varistors were examined by means of scanning electron microscopy, transmission electron microscopy, and powder X-ray diffractometry. The glass phase was originally amorphous, but crystallized as an intergranular layer in the sintered and furnace-cooled samples. This crystallized phase was a zinc borate phase (5ZnO·2B₂O₃), which was identified by X-ray diffractometry, transmission electron microscopy, and Auger electron spectroscopy. The zinc borate phase at the grain boundary of ZnO–glass samples enhanced the nonohmic characteristics of the ceramic varistors.     

Effect of NiO doping on grain growth and electrical properties of ZnO-based varistors

The effects of NiO content on the grain growth and the electrical properties of the ZnO varistors were studied. The effect on the grain growth was characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometer, while the effects on the electrical properties were investigated by varistor tester, pulse surge tester and precision impedance analyzer. The results showed that the growth of the (0002) plane of the ZnO varistors was inhibited by doping NiO, which improved the electrical properties of the varistors, especially the surge shock stability. The sample doped with 1.56 mol% NiO exhibited excellent electrical properties with breakdown voltage gradient of 184.0 V/mm, nonlinear coefficient of 72.7, leakage current of 0.37 µA, clamp voltage ratio of 2.20 under 8/20 μs waveform impact of 20 kA and change rates of positive and negative breakdown voltages of < 4% under 20 times impacts of 20 kA.     

氧化锌电阻片中气孔的产生与预防

氧化锌电阻片中的气孔严重地影响了电阻片自身的电性能,本文从几方面阐述了电阻片中气孔的产生与预防办法,为电阻片生产工艺的完善提供了有用的参考。     

Processing and characterizations of flash sintered ZnO-Bi2O3-MnO2 varistor ceramics under different electric fields

The dense ZnO-Bi₂O₃-MnO₂ (ZBM) varistors were prepared by flash sintering under electric fields ranging from 200 V/cm to 400 V/cm at constant heating rate (CHR) and constant furnace temperature (CFT), respectively. The structure and electrical properties of the ZBM varistors were studied via the XRD, SEM and a DC parameter instrument. The onset temperature and incubation time of flash sintering decrease with increasing electric field. The effects of the maximum limiting current on the density of the samples were also investigated. The results showed that the density of samples increase with the increasing current values. The improved electrical characteristics were obtained during constant furnace temperature flash sintering. The ZBM varistor ceramics exhibited superior comprehensive electrical characteristics under a field of 250 V/cm, in which the nonlinear coefficient is 26.4, the threshold voltage and the leakage current is 466 V/mm and 12.32 μA, respectively.     

Preparation and electrical properties of multilayer ZnO varistors with water-based tape casting

Multilayer ZnO varistors were prepared by water-based tape casting with water-soluble acrylic as binders. Zeta potentials of the doped ZnO suspensions as a function of pH with and without dispersant were measured. Viscosity measurements were used to find the optimum dispersant concentration needed to prepare a stable slurry. Viscosity properties of the tape casting slurry were investigated. The results showed that aqueous acrylic binders have shear thinning properties suitable for tape casting of ceramic powders. Scanning electron microscopy (SEM) studies revealed that the green sheets have a smooth defect-free surface and that the multilayer varistor (MLV) ceramics prepared by water-based tape casting have a fine grain microstructure with a uniform grain size and dopant distribution. The multilayer ZnO varistors prepared by water-based tape casting display comparable good electrical properties to those prepared by solvent-based tape casting. This is believed to be attributed to the well dispersed water-based slurry, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. Therefore, water-based tape casting is suitable for the manufacture of high performance multilayer ZnO varistors.     

Synthesis mechanism of low-voltage praseodymium oxide doped zinc oxide varistor ceramics prepared through modified citrate gel coating

High demands on low-voltage electronics have increased the need for zinc oxide (ZnO) varistors with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage. However, trade-off between breakdown voltage and grain size poses a critical bottle-neck in the production of low-voltage varistors. The present study highlights the synthesis mechanism for obtaining praseodymium oxide (Pr(6)O(11)) based ZnO varistor ceramics having breakdown voltages of 2.8 to 13.3 V/mm through employment of direct modified citrate gel coating technique. Precursor powder and its ceramics were examined by means of TG/DTG, FTIR, XRD and FESEM analyses. The electrical properties as a function of Pr(6)O(11) addition were analyzed on the basis of I-V characteristic measurement. The breakdown voltage could be adjusted from 0.01 to 0.06 V per grain boundary by controlling the amount of Pr(6)O(11) from 0.2 to 0.8 mol%, without alteration of the grain size. The non-linearity coefficient, α, varied from 3.0 to 3.5 and the barrier height ranged from 0.56 to 0.64 eV. Breakdown voltage and α lowering with increasing Pr(6)O(11) content were associated to reduction in the barrier height caused by variation in O vacancies at grain boundary.