能量脉冲对ZnO压敏电阻静态老化性能的影响

研究了能量脉冲对高能ＺｎＯ压敏电阻在可控硅整流电压下的静态老化性能的影响以及可控硅整流电压的过电压对压敏电阻的作用。过电压使压敏电阻流过频率为３００Ｈｚ的脉冲电流，从而使晶界势垒高度下降和晶粒导电性增加；经受能量脉冲后的压敏电阻的静态老化电流增长速度远大于未经能量脉冲的压敏电阻的静态老化电流增长速度，即能量脉冲使静态老化性能严重变差。     

能量脉冲对高能ZnO压敏电阻静态老化性能的影响

研究了能量脉冲对高能ＺｎＯ压敏电阻在可控硅整流电压下的静态老化性能的影响以及可控硅整流电压的过电压对压敏电阻的作用，过电压使压敏电阻流过频率为３００Ｈｚ的脉冲电流，从而使晶界势垒高度下降和晶粒导电性增加；经受能量脉冲后的压敏电阻的静态老化电流增长速度远大于未经能量脉冲的压敏电阻的静态老化电流增长速度，即能量脉冲使静态老化严重变差。     

高能ZnO压敏电阻在能量脉冲下的动态老化

研究了用于水轮发电机灭磁与过电压保护的高能ＺｎＯ压敏电阻在贮能电感释放的能量脉冲作用下的老化现象，能量脉冲可以分解为直流电场和能量两个分量。能量脉冲后，压敏电阻的特征电压，非线性系数和预击穿区Ｖ－Ａ特性都发生跌落，而且这种跌落随脉冲次数增加而增加，能量脉冲使压敏电阻发老化机理是发生在晶粒耗尽层中和富铋晶界层中的离子迁移使双Ｓｃｈｏｔｔｋｙ势垒降低。     

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。     

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.     

稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻性能的影响

采用低温固相化学反应法制备了Pr2O3掺杂的ZnO纳米复合粉体,并用此粉体在不同烧结温度下制备了高压ZnO压敏电阻.采用X射线衍射、比表面测试、透射电镜、扫描电镜等手段对制备的ZnO纳米复合粉体及高压ZnO压敏电阻进行了表征,并与未掺杂ZnO压敏电阻进行了对比研究,探讨了稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻电性能的影响机制.结果表明:较低的烧结温度(1030～1130℃)时,掺杂的稀土氧化物Pr2O3偏析于ZnO晶界中,有活化晶界、促使晶粒生长的作用;同时,Pr2O3掺杂导致1080℃烧结的ZnO压敏陶瓷体中晶体相互交织形成晶界织构,比未掺杂的更均匀和致密,这有助于高压ZnO压敏电阻晶界性能的改善,从而提高其综合电性能.当烧结温度为1080℃时,Pr2O3掺杂的高压ZnO压敏电阻的综合电性能最佳:电位梯度为864.39 V/mm,非线性系数为28.75,漏电流为35 μA.     

稀土氧化物Pr2O3掺杂对高压ZnO压敏电阻性能的影响

采用低温固相化学反应法制备了Pr₂O₃掺杂的ZnO纳米复合粉体, 并用此粉体在不同烧结温度下制备了高压ZnO压敏电阻。采用X射线衍射、 比表面测试、 透射电镜、 扫描电镜等手段对制备的ZnO纳米复合粉体及高压ZnO压敏电阻进行了表征, 并与未掺杂ZnO压敏电阻进行了对比研究, 探讨了稀土氧化物Pr₂O₃掺杂对高压ZnO压敏电阻电性能的影响机制。结果表明: 较低的烧结温度(1030～1130 ℃)时, 掺杂的稀土氧化物Pr₂O₃偏析于ZnO晶界中, 有活化晶界、 促使晶粒生长的作用; 同时, Pr₂O₃掺杂导致1080 ℃烧结的ZnO压敏陶瓷体中晶体相互交织形成晶界织构, 比未掺杂的更均匀和致密, 这有助于高压ZnO压敏电阻晶界性能的改善, 从而提高其综合电性能。当烧结温度为1080 ℃时, Pr₂O₃掺杂的高压ZnO压敏电阻的综合电性能最佳: 电位梯度为864.39 V/mm, 非线性系数为28.75, 漏电流为35 μA。     

Cr2O3对(Co,Ta)掺杂的SnO2压敏电阻电学特性的影响

研究了Cr对(Co,Ta)掺杂的SnO2压敏材料电学性质的影响.当Cr2O3的含量从0增加到0.15mol%时,(Co,Ta)掺杂SnO2压敏电阻的击穿电压从206V/mm增加到493V/mm;1kHz时的相对介电常数从1968猛降至498;晶界势垒高度分析表明,SnO2晶粒尺寸的迅速减小是样品击穿电压增高、相对介电常数急剧降低和电阻率迅速增大的主要原因.对Cr含量增加引起SnO2晶粒减小的原因进行了解释.掺杂0.15mol% Cr2O3的SnO2压敏电阻非线性系数为24,击穿电压达498V/mm,在高压保护领域有很好的应用前景.     

掺杂TiO2的ZnO压敏电阻正电子寿命谱研究

利用正电子湮灭技术(PAS)和扫描电子显微镜(SEM),分析了掺杂TiO2的ZnO压敏电阻的晶界缺陷,以及不同降温速率对晶界特性的影响.实验结果表明,向样品中掺杂TiO2或者快速冷却样品,都能使得样品晶界处Zn空位团尺寸变大,浓度减小.     

B_2O_3掺杂氧化锌压敏电阻烧结工艺的微观结构和电气特性

研究了在不同烧结温度下制备的直流ZnO压敏陶瓷的微观结构和电气特性。通过扫描电子显微镜,电流-电压的伏安特性,电容-电压和从小电流到大电流范围的X射线衍射图测量不同烧结温度下样品的电气参数和微观结构。实验结果表明在1150℃下烧结的样品晶粒尺寸比较均匀,非线性系数和泄漏电流分别为66和0.96μA/cm~2,电压梯度为381 V/mm,直流氧化锌压敏电阻的综合性能达到最优。随着烧结温度的升高,ZnO晶粒尺寸(d)会变大,导致单位长度内晶界数量减少使氧化锌压敏电阻的电压梯度减少。晶粒的尺寸的增加可以阻断三角区的互联互通,使泄漏电流减小。当烧结温度高于1 150℃时,会造成Bi_2O_3的挥发使非线性系数降低。获得电压梯度为381 V/mm的直流氧化锌压敏电阻有利于优化超高压避雷器结构、电阻柱上的电位分布更加均匀。综上所述,制备B_2O_3掺杂的氧化锌压敏电阻配方最佳的烧结温度为1 150℃。     

Electrical properties and degradation improvement of ZnO varistors doped with PbO-B2O3 based glasses

The effects of PbO-B₂O₃ based glasses on the nonlinear exponent, leakage current, cooling rate sensitivity and degradation behaviour of ZnO varistors were investigated. Measurements of capacitance-voltage (C-V), current-voltage (I-V), dielectric properties, degradation behaviour as well as microstructural observations, were performed. It was found that leakage current, cooling rate sensitivity and degradation behaviour were generally improved, while the nonlinear exponent was only affected slightly by the glass dopants. The effects of glass dopant were explained by the lower dissolution of manganese and cobalt in ZnO grains, which increased donor density, trap density, and hence barrier height. The improved degradation behaviour caused by addition of glass dopant was interpreted by a decrease of concentration of zinc vacancy which tended to lower barrier height as it moved away from the boundary layer under the electric field.     

Effects of annealing on the grain boundary potential barrier of ZnO varistor

Effects of post heat treatment on the potential barrier at the grain boundaries of ZnO varistors will be discussed from the viewpoints of the surface state density and the donor concentration. Leakage current of varistors at a low electric field increases by annealing at 750° C in air or nitrogen due to the lowered barrier height corresponding to the decrease of surface state density, which may be explained with the phase transformation of the bismuth-rich intergranular layer. It is also observed that theV-I non-linearity of the annealed ceramics is generally recovered as the annealing (in air) time is extended. This can be explained by the heightened barrier potential attributed to the decrease of donor concentration in ZnO grains, which was confirmed by aid ofC-V measurements. The decrease of donor concentration by the annealing in air can be considered to be responsible for the thermal oxidation of interstitial zinc ions or oxygen vacancies.     

受主掺杂对ZnO片式压敏电阻材料性能的影响

研究了一价受主Li^＋对ZnO片式压敏电阻材料的电性能和晶界电参数的影响。材料中添加适量的Li^＋离子,可提高压敏电阻的非线性系数、改进器件的漏电流特性。当Li^＋离子添加量从0增加至300mol／ppm时,晶界势垒高度φB由0.7eV增加为0.87eV,晶粒中载流子浓度ND由2.2×10^23／m^3下降为8.5×10^22／m^3,ZnO的电阻率ρg由1.02Ω·cm增加为1.98Ω·cm。     

Electrical properties and degradation phenomena of glass-doped ZnO chip varistors

Several glass additives with compositions in the PbO---B₂O₃---ZnO---SiO₂ system were applied to multilayer type ZnO ceramic chip varistors which had been manufactured using the ceramic green-sheet lamination technique. Measurements of capacitance-voltage (C-V), current voltage (I-V) and degradation behavior, as well as microstructural observations, were performed. It was found that specimens into which the above-mentioned glasses were incorporated had good surgewithstanding capability, with the exception of samples including Zn---B---Si glass. The electrical properties of speciments deteriorated gradually with increasing glass content. The addition of glasses improved the thermal stability of ZnO varistors except for G4 glass-doped sample (60 w/oPbO−12 w/oB₂O₃−605w/oZnO). Stable varistors with good nonlinearity parameters were obtained by combining the glass compositions and other additives.     

Correlation of grain boundary characteristics with electrical properties in ZnO–glass varistors

Grain boundary glass crystallinity was studied to determine its effect on the electrical properties of ZnO–glass varistors. Si-rich glass at the grain boundary layer transformed into a crystalline zinc silicate phase after heat treatment. However, glass without any SiO₂ was not recrystallized and remained amorphous following the same process. Variations in non-ohmic behaviour of the samples with three different glass additives are attributed to their different crystallinity. According to a proposed defect reaction equation, strong pinning of the barrier height was found in ZnO–glass varistors with crystallized glass phase. This would ultimately cause an increase in the α values, grain boundary barrier height, breakdown voltage per grain and device stability. If charged ions such as V _o ^? , are present due to the formation of the crystalline intergranular phase, the grain boundary barrier height and device stability would initially be enhanced by increased density of interface states, later decreasing due to the migration of zinc interstitials Zn _i ^?? under electrical stress. Furthermore, results of deep-level transient spectroscopy, together with dielectric loss and Auger linescan analyses detected three electron traps: L2 is associated with the energy level of the second ionization of interstitial zinc atoms; and the broadness of the trap L3 is analogous to the energy level of the first ionization of oxygen vacancies; trap L1 has been identified as native defects.     

Effects of cobalt doping on the electrical characteristics of Al-doped ZnO varistors

The effects of cobalt additive on the electrical characteristics of the Al-doped ZnO varistors are studied in this paper. The current-voltage characteristics of the varistor samples have been investigated in a range from small to large current. With the amount of the doped cobalt increased, the leakage currents of the Al-doped ZnO varistors are inhibited, and their nonlinear coefficients increase remarkably as well. In addition, their breakdown electric fields increase in a small extent and their residual voltage ratios change slightly. Furthermore, the donor densities and the barrier heights of samples decrease with the cobalt content increased. The XRD patterns show that the Bi-rich phase and the willemite phase vary obviously in the varistor samples with various content of cobalt additive.     

TiO2压敏电阻的研究与应用

为了更好地研制和应用压敏电阻元件,介绍了TiO2压敏电阻的基本性质,压敏机理以及研究现状,阐述了制备过程中掺杂物种、掺杂浓度、烧结温度、粉体材料等因素对二氧化钛压敏电阻性能的影响.研究表明,TiO2系列压敏电阻具有较低的压敏电压、较高的非线性系数、超高的介电常数,并且制备工艺简单.TiO2系列压敏电阻能有效弥补SrTiO3和ZnO系压敏电阻器所存在的不足之处,是低压压敏陶瓷的研发方向.