铝掺杂对氧化锌压敏陶瓷电性能的影响

研究了微量铝(Al)掺杂对氧化锌(ZnO)压敏陶瓷显微结构、电性能和本征点缺陷浓度等方面的影响及其作用机理。研究结果表明, 介电损耗峰值能够在一定程度上反映ZnO压敏陶瓷本征点缺陷浓度, 微量Al掺杂能够引起ZnO压敏陶瓷本征点缺陷浓度的显著降低。氧空位缺陷对应的损耗峰峰值从88.82下降到1.74, 锌填隙缺陷对应的损耗峰峰值从133.38下降到8.14。随着Al掺杂量的增加, ZnO压敏陶瓷平均晶粒尺寸从9.15 μm逐渐下降到6.24 μm, 而压敏电压从235 V/mm逐渐提高到292 V/mm。可见Al掺杂抑制了ZnO压敏陶瓷中本征点缺陷的形成, 而本征缺陷浓度的降低导致材料显微结构和电性能发生明显变化。本文阐述了Al掺杂对ZnO压敏陶瓷本征缺陷的影响机理, 建立了ZnO压敏陶瓷显微形貌、电性能、介电性能和本征点缺陷之间的联系。     

Y2O3掺杂对低压氧化锌压敏电阻材料结构和电学性能的影响

通过掺杂研究了微量Y2O3对低压氧化锌压敏电阻的电性能影响,并采用SEM测试手段对其微观组织结构进行了分析研究,从理论上探讨了Y2O3影响低压氧化锌压敏电阻电性能与组织的机理.研究结果表明,在0～0.07%(摩尔分数)掺杂范围内,随着Y2O3含量的增加,低压氧化锌压敏电阻的电场强度明显提高;当Y2O3含量超过0.07%时,电场强度又呈下降趋势.低压氧化锌压敏电阻掺杂Y2O3后,非线性指数α增大,漏电流IL减小,但当掺杂量在0.06%～0.09%(摩尔分数)的范围内,漏电流IL和非线性指数α的变化不大.其原因是Y2O3加入到氧化锌压敏电阻中,Y主要以固溶的形态分布于ZnO晶内和晶界处,使ZnO晶体的自由电子浓度增大,进而使填隙锌离子Zni的总浓度下降,引起填隙锌离子的传质能力下降,抑制了ZnO晶粒的生长,因而晶粒尺寸随Y2O3掺杂量的增加而减小.     

掺杂稀土氧化物的ZnO-Bi2O3系压敏陶瓷中的"软心"

研究了掺杂Ce2O3和Gd2O3对ZnO—Bi2O3系压敏陶瓷电气性能的影响，发现大尺寸试样的内层电位梯度明显低于表层，即表现出“软心”特征．“软心”导致试样平均电位梯度随着试样几何尺寸的增大而下降．沿轴向晶粒尺寸没有明显的差异．根据沿轴向截取的等厚薄片的电流与温度的关系，发现表层的晶界势垒高度比内层的高．这种晶界势垒高度的非均匀分布可能与添加稀土氧化物后造成的氧元素分布不均匀有关．     

新型压敏陶瓷材料的研究与进展

ZnO压敏材料问世50年来,新型压敏材料的研发一直备受各国研究者和业界的关注。根据本研究组的一些研究结果,结合有关文献报道对国内外压敏陶瓷材料研究发展现状作了一个回顾与综述,指出随着科学技术的飞速发展,无论是SrTiO4系压敏陶瓷、TiO2系压敏陶瓷、低压ZnO压敏电阻和高压ZnO阀片还是多层片式ZnO压敏电阻器,各种新型压敏陶瓷材料和压敏元件的研发都取得了很大进展。然而,近年来国外在高性能、高梯度ZnO阀片和在新型SnO2压敏材料的醒目进展需要引起国内业界的极大关注。     

两步法制备Y_2O_3掺杂ZnO压敏瓷

采用两步烧结制备了Y_2O_3掺杂ZnO压敏瓷,其电位梯度为863～1330V/mm,非线性系数为27.0～49.7,漏电流为0.55～1.13μA.研究结果表明,当Y_2C_3的掺杂量为1.00%(摩尔分数)时,压敏瓷电性能最好,电位梯度为1330V/mm,非线性系数为49.7,漏电流为0.76μA.     

添加Bi2WO6对ZnO基压敏陶瓷电学性能的影响

用传统固相反应法研究了添加Bi₂WO₆(x=0%~9%,质量分数)对ZnO基压敏陶瓷的微观结构、压敏性能和介电性能的影响。结果表明：掺入适量的Bi₂WO₆能促进ZnO压敏陶瓷晶粒均匀生长、提高微观结构的均匀性、降低压敏场强和提高非线性系数;同时,Bi₂WO₆的添加可提高ZnO晶粒表面吸附氧的含量,从而提高界面态密度和势垒高度以及ZnO基压敏陶瓷的非线性特性。Bi₂WO₆的添加量为7%的ZnO基压敏陶瓷,其综合性能为：E_{1 mA}=263 V/mm,α=53,J_L=3.50 μA/cm²,φ_b=11.52 eV。     

钛的复合掺杂对ZnO压敏电阻器性能的影响

本文研究了钛以不同的复合物加入时，对ZnO压敏电阻器电性能的影响。实验表明，不同的复合物掺杂对ZnO压敏电阻器电性能影响规律不同，当钛的复合物在压敏电阻器烧结过程中有利于钛溶于晶界处的富铋液相中时，则有利于晶粒的生长。     

保温时间对ZnO压敏陶瓷电学性能的影响

采用固相烧结法制备了ZnO-Pr₆O₁₁-Co₂O₃-Cr₂O₃-Er₂O₃-SiO₂压敏陶瓷，并研究了保温时间对ZnO压敏陶瓷的物相、微观形貌、压敏特性和阻抗特性等的影响。结果表明：随着保温时间变长，平均晶粒尺寸逐渐增大。保温3 h的ZnO压敏陶瓷综合性能最好，非线性系数和晶界势垒高度均达到最大，分别为16.9和0.37 eV,击穿场强和晶界电阻率分别为384.3 V/mm和17 400 MΩ·cm,且漏电流最小，为1μA。同时，晶界处带负电的Zn_1.9SiO₄相的存在对晶粒间双肖特基势垒的形成有重要影响。     

Na对SnO2-CoO-Nb2O5系压敏材料电学性能的影响

研究了Na对新型(Co，Nb)掺杂SnO2压敏材料微观结构和电学性质的影响。当Na2CO3的含量从0增加到1.2mol％时，(Co，Nb)掺杂SnO2压敏电阻的击穿电压从275V／mm增到919V／mm。样品的微观结构分析发现，当Na2CO3的含量从0增加到1．2mol％时，SnO2的晶粒尺寸明显的变小。晶界势垒高度测量揭示，SnO2的晶粒尺寸的迅速减小是压敏电压急剧增高的原因。对Na含量增加引起SnO2晶粒减小的根源进行了解释。掺杂0．4mol％Na2CO3的SnO2压敏电阻非线性系数达28．4．击穿电压为755V／mm，掺杂1.2mol％Na2CO3的SnO2压敏电阻非线性系数为11．5，击穿电压高达919V／mm，它们在中高压保护领域会有很好的应用前景。本文并指出替代Sn的受主离子Na不应处于SnO2晶格中，而是处于间界上，从而进一步解释了压敏电压急剧增高的原因。     

高电位梯度ZnO压敏电阻片的研究进展

从材料组成、显微结构控制和制备工艺等方面综述了国内外高电位梯度ZnO压敏电阻片的研究进展,并展望了提高ZnO压敏电阻片电位梯度和通流容量的途径.采用三价过渡金属离子掺杂、减小添加剂粉料颗粒粒度以及控制合理的烧成制度,能明显减小晶粒尺寸,降低气孔率,增加晶界数目,提高晶界势垒,从而有效提高ZnO压敏电阻片的电位梯度.     

The effect of Cr2O3 additive on the electrical properties of ZnO varistor

The effect of Cr2O3 additive on the leakage conduction and threshold voltage characteristics of bismuth-based ZnO ceramic varistor was studied. The leakage conduction in the voltage range below the threshold voltage increased with increasing Cr2O3 concentration and is attributed to the Schottky barrier height. It was found that the increases in the apparent threshold voltage were associated with the lowered donor concentration in the depletion region of the ZnO grain. These results were obtained by measuring C–V characteristics, the breakdown voltage at the current density of 10-3 A cm-2 and the microstructure of ZnO ceramics. This revised version was published online in November 2006 with corrections to the Cover Date.     

Characterization of ZnO Based Varistor Derived from Nano ZnO Powders and Ultrafine Dopants

Nanosized ZnO powders were prepared with a two-step precipitation method. The average size of ZnO particles was about 80 nm and their size distribution was narrow. Combining with ultrafine additive powders, ZnO base varistor was produced via an oxide mixing route. ZnO varistor derived from normal reagent grade starting materials was investigated for comparison purpose. Outstanding microstructure of the ZnO varistor derived from nanosize ZnO powders and ultrafine dopants was obtained: uniform distribution of fine ZnO grains (less than 3 microns), grain boundary and the dopant position. Higher varistor voltage (U=492 V/mm) and nonlinear coefficient (α=56.2) as well as lower leakage current (TL=1.5 μuA) were achieved. The better electrical properties were attributed to the uniform microstructure, which in turn led to stable and uniform potential barriers. Also this improved technique is more feasible for producing ZnO nanopowders and resulting varistor in large scales.     

ZnO籽晶对ZnO压敏陶瓷微观结构和电性能的影响

本文研究了ＺｎＯ籽晶的制备，探讨了昌对ＺｎＯ压敏陶瓷材料微观结构及压敏电压。通流容量。非线性一系民性能的影响。结果表明，通过掺加ＺｎＯ籽晶，可有效地控制材料中ＺｎＯ昌粒生长入材料微观结构。达到降低材料压敏电压和提高通流容量的目的。     

Fe元素对ZnO陶瓷晶界电性能的影响机理研究

研究了不同浓度的Fe2O3掺杂对ZnO陶瓷压敏特性的影响,实验表明,随Fe掺杂量增加,ZnO平均晶粒尺寸逐渐变大,压敏电压升高,非线性系数先增大后减小,漏电流先减小后增大.分析认为,Fe元素掺杂对ZnO陶瓷电性能的影响不仅与电子的能级有关,还与其自旋特性紧密相连.ZnO中掺杂的Fe元素随机取代其中的部分Zn原子后,Fe3+或Fe2+在ZnO中产生局域磁矩,会对与其取向不同的自旋电子产生强的散射,这样可增大ZnO陶瓷的电阻率,Fe元素在晶界的偏析可产生和提高其非线性特性.     

低压ZnO压敏电阻材料研究及发展概况

概述了低压ZnO压敏电阻材料的制备工艺、应用技术、粉料制备,以及晶界特性、导电模型、老化机理的研究进展和研究中存在的问题,并对以后的发展方向进行了展望。着重讲述了掺杂物对烧结过程、晶粒生长和晶界结构的作用以及显微结构（晶粒大小及晶界状态）均匀性对电笥能和老化特性的影响,并提出了改善老化性能的关键措施。     

Microstructure and electrical properties of Pr<Subscript>6</Subscript>O<Subscript>11</Subscript> doped ZnO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-based varistors

The microstructure and electrical properties of ZnO-Bi₂O₃-based varistor ceramics doped by Pr₆O₁₁ in the content range of 0–5.49 wt% were investigated at different sintering temperatures (1,100, 1,150, 1,175, 1,200 °C). The increase of sintering temperature leads to more dense ceramics, which increases the nonlinear property, whereas it decreases the voltage-gradient and leakage current. With increasing Pr₆O₁₁ content, the breakdown voltage increases because of the decreases of ZnO grain size. The improvement of non linear coefficient together with the decrease of leakage current are related to the uniformly distribution of secondary phases along the grain boundaries of the ZnO. The varistors sintered at 1,175 °C with the 3.37 wt% Pr₆O₁₁ doping possess the best electrical properties: the varistor voltage, nonlinear coefficient, and leakage current are 340 V/mm, 46 and 0.63 μA, respectively.     

Low-temperature sintering and electrical properties of Co-doped ZnO varistors

ZnO–Bi₂O₃–B₂O₃-based varistors doped with each kind of cobalt oxides were prepared by conventional ceramic processing. The effects of CoO, Co₂O₃ and Co₃O₄ on the microstructure and the electrical characteristics of varistor samples sintered at 880 °C were investigated separately. Analysis of microstructure indicated the cobalt cations were distributed both in grain regions and grain boundary regions and no crystalline phases containing cobalt were detected in XRD patterns for the samples with various cobalt oxides. All these cobalt oxides could effectively enhance the varistor performance by effectively increasing the nonlinear coefficient and lowing the leakage current, while the breakdown voltage fields increased slightly. Capacitance–voltage characteristics showed the potential barriers of varistor samples increased with the addition of each cobalt oxide. It was found that the addition of same amount of cobalt cations in various cobalt oxides had a different effect on the varistor samples. Best electrical properties were obtained for the varistor sample containing Co₃O₄, in which the nonlinearity coefficient is 28.5, the leakage current density is 3.4 μA and the breakdown voltage field is as low as 260 V/mm.     

B2O3和Al2O3共同掺杂ZnO压敏陶瓷的性能

研究了B₂O₃(B)和Al₂O₃(Al)共掺杂对ZnO压敏陶瓷电学性能和微观结构的影响。结果表明,共掺杂B和Al的ZnO压敏陶瓷,具有低泄漏电流、高非线性和低剩余电压等优良电性能。B和Al的掺杂率为3.0%(摩尔分数)和0.015%(摩尔分数)的ZnO压敏陶瓷,其最佳样品的电参数为：击穿电压E_{1 mA}＝475 V/mm;泄漏电流J_L=0.16 μA/cm²;非线性系数α=106;剩余电压比K = 1.57。     

ZnO纳米粉对压敏陶瓷材料显微结构和电学特性的影响

用ｓｏｌ－ｇｅｌ方法制备掺杂的ＺｎＯ纳米粉体，分析讨论了这种粉体对材料显微结构，材料电学特性如非线性系数，压敏电压和介电特性的影响，与传统方法制成的粉体相比，ｓｏｌ－ｇｅｌ方法制成的纳米粉人有掺杂均匀，晶粒尺寸分布均匀，其电学特性得到较大提高。