Fe_2O_3掺杂对ZnO-Pr_6O_(11)系压敏电阻材料电学性能的影响

通过烧结法制备了Fe2O3掺杂的ZnO–Pr6O11压敏电阻材料,研究了Fe2O3掺杂量对ZnO–Pr6O11系压敏电阻材料电学性能的影响。实验表明:当Fe2O3掺杂量小于0.005%(摩尔分数,下同)时,ZnO–Pr6O11系压敏电阻材料的非线性系数和压敏电压随Fe2O3掺杂量增大而逐渐提高。当Fe2O3掺杂量为0.005%时,压敏电压达到最大值571V/mm,非线性系数达到最大值26。当Fe2O3掺杂量大于0.005%时,非线性系数和压敏电压均急剧下降。过量Fe2O3使ZnO压敏电阻材料非线性下降的主要原因是:Fe元素偏析在晶界处,提供额外载流子降低了晶界电阻率,同时晶界处PrFeO3相的堆积会破坏晶界结构,从而影响压敏电阻材料的电学性能。     

室温固相合成掺杂ZnO纳米粉体制备ZnO压敏电阻

以金属离子盐和草酸为原料,采用室温固相化学反应合成掺杂ZnO前驱物,根据DSC-TG分析结果,将其在450℃热分解2 h,得到掺杂ZnO粉体,并用此粉体制备了片式ZnO压敏电阻。借助XRD、TEM、BET等检测手段对粉体产物的物相、形貌、粒度等进行了表征。研究了烧结温度对ZnO压敏电阻电性能的影响。结果表明,所制备的粉体为平均粒径24 nm左右、颗粒呈球状、分散性好的纤锌矿结构掺杂ZnO。在1 080℃烧结时,ZnO压敏电阻的综合电性能达到最佳,电位梯度为791.64 V/mm,非线性系数为24.36,漏电流为43μA。     

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。     

CeO2掺杂Pr6O11系氧化锌压敏电阻的研究

探讨了添加不同CeO2含量对Pr6O11系ZnO压敏电阻显微结构及电性能的影响,以期能满足特高压用高电位样度的应用需求.结果表明:随着CeO2掺杂量的增加,ZnO-Pr6O11系压敏电阻电位梯度和非线性系数有明显的提高,在掺杂量为1.0mol%时达到峰值,分别为548V/mm和42.XRD、SEM检测分析表明,CeO2并不与ZnO及其他氧化物生成新相,而是以CeO2的形式独立存在,抑制了ZnO的生成,致使填隙锌离子的传质能力下降,从而减小ZnO晶粒尺寸,并改善了压敏电阻的晶界结构和成分.     

高梯度氧化锌压敏电阻的制备

采用我公司自制的纳米材料,并添加Ce O2、La2O3、Y2O3、Sm2O3稀土氧化物对氧化锌压敏电阻进行掺杂改性,研究了不同稀土氧化物对氧化锌压敏电阻性能的影响。结果表明,在同等掺杂的情况下,1120℃左右烧结成瓷,制备的氧化锌压敏电阻表现出不同的电性能,其中以Y2O3掺杂改性效果最佳,其能量吸收密度达到284 J/cm3,电位梯度达到308 V/mm,漏电流为4μA,性能优于其他稀土氧化物掺杂改性,更优于传统阀片。     

ZnO-玻璃系压敏电阻的微观结构

制备了ZnO-玻璃系压敏电阻,用SEM,TEM,EPMA等微观分析手段研究了ZnO-玻璃系压敏电阻的微观结构,相组成与元素分布.ZnO-玻璃系压敏电阻由ZnO主晶相、Zn7Sb2O12尖晶石相以及粒间相组成.Co离子有较大部份已溶入ZnO晶粒内,而Mn离子只有少量进入ZnO晶粒之表层,Sb离子主要分布在粒间处.晶界层厚度约为10～100 am,其成分与ZnO晶粒内成分基本相近.在一定的烧结温度下,粒间相中还生成了Zn-B结晶相,该相的产生有利于增强压敏电阻的非线性特性.     

高能球磨法制备氧化锌压敏电阻的低温烧结

粗晶氧化锌(ZnO)混合粉经5 h高能球磨,其晶粒尺寸减小至43 nm.高能球磨增强了混合粉的烧结性,使其烧结温度降至800℃.扫描电镜及各个烧结温度下电性能和密度的实验结果证明:800℃烧结的压敏电阻具有最大的密度和良好的电性能,其相对密度达98.94%,电位梯度为1 528 V/mm漏电流为20μA,非线性系数为15.4,晶粒尺寸为1.4μm.     

ZnO片式压敏电阻厚膜中Cr_2O_3含量的优化(英文)

研究三氧化二铬(Cr2O3)对氧化锌(ZnO)片式压敏电阻厚膜物相结构、微观结构和电性能的影响。X衍射分析表明:Cr2O3降低Bi4Ti3O12相的分解温度,并最终影响陶瓷厚膜的致密度、晶粒尺寸及电性能。当烧结温度为880℃时,Cr2O3摩尔(下同)掺量为0.3%的陶瓷厚膜能够得到良好性能:体积密度ρv=5.52g/cm3,晶界势垒Φb=0.116eV,非线性系数α=24.8。研究烧结温度与片式压敏电阻微观结构和电性能的关系,Cr2O3掺量为0.3%的片式压敏电阻在880℃烧结时,能够获得最佳电性能:压敏电压V1mA=25V,α=23.6,漏电流Il=2.8μA。该片式压敏电阻的低烧结温度和高非线性在工业生产中具有很大优势。     

真空烧结对高压厚膜型ZnO压敏陶瓷的影响

采用真空烧结的方法制备出高电位梯度的厚膜型ZnO压敏陶瓷,并研究了多次真空烧结对高压厚膜型ZnO压敏陶瓷的影响。实验结果表明,多次真空烧结使试样的电学性能产生先劣化后优化的变化趋势。真空烧结5次后,试样的电位梯度为2890.9V/mm,漏电流为87.9μA,非线性系数为9.0,晶粒尺寸在2μm左右。晶粒中氧原子百分含量的降低表明真空烧结5次后,晶粒、晶界间发生了氧原子的转移,使试样宏观电学性能得到改善。     

TiO2掺杂对ZnO压敏电阻低压化过程的影响

近年来，加入晶粒助长剂TiO2以实现低压化的低压ZnO压敏电阻发展迅速。实验所用配方为掺杂TiO2的98.3％ZnO-0.7％Bi2O3-1.0％TiO2(摩尔分数)和相应无TiO2掺杂的配方，在900～1200℃下烧结制备样品。给出了相分析、半定量分析及电性能测试结果。发现TiO2可以有效促进ZnO晶粒长大，降低压敏电压梯度。1100℃下，TiO2掺杂试样的平均晶粒尺寸为56.4μm，远大于无TiO2掺杂的31.8μm。大部分TiO2首先与Bi2O3反应生成Bi4(TiO4)3液相，这大大促进了ZnO晶粒生长。高于1000℃时Bi4(TiO4)3分解，分解出的TiO2与ZnO发生反应，生成Zn2TiO4尖晶石相，晶粒生长受阻，直至停止。     

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。     

ZnO掺杂量与烧结温度对SnO2–Ta2O5–ZnO压敏变阻材料性能的影响

以SnO2、Ta2O5和ZnO粉为原料,通过传统陶瓷固相反应烧结法制备了压敏变阻材料,实验中ZnO含量为0～2.00%(摩尔分数),烧结温度控制在1 300～1500℃并保温2 h。研究了ZnO掺杂量和烧结温度对材料的组成、微观结构和电学性能的影响。结果表明:在温度一定条件下,随着ZnO掺杂量的增加,材料的非线性系数、压敏电压先增大后减小;在ZnO含量一定时,随着烧结温度从1 300℃升至1 450℃,材料的非线性系数、压敏电压先增大后减小。ZnO掺杂量为0.50%时,在1450℃烧结得到的样品的非线性系数最高(6.2),漏电流最小(262μA/cm2),压敏电压较高(83V/mm)。     

水基流延片式ZnO压敏电阻器低温共烧工艺及其性能

用环境扫描电子显微镜（ESEM）、X射线衍射（XRD）和X射线能谱（EDXS）等研究了水基流延片式ZnO压敏电阻器的低温共烧工艺及其对微观结构和电学性能的影响规律。ESEM分析结果表明：当等静压压力为60 MPa时,Ag电极与流延膜生坯界面结合紧密,Ag电极分布连续,900℃共烧时,未出现开裂、分层,两者收缩率接近。EDXS和XRD分析结果表明：900℃共烧时,Ag在片式压敏电阻器中以单质形式存在,流延膜与Ag电极化学兼容性良好,且在共烧界面处未发现有明显的Ag离子扩散。该流延膜可以与Ag电极在900℃时实现低温共烧,用此制备的片式ZnO压敏电阻器具有良好的压敏性能：压敏电压V1mA=6.1 V,非线性系数α=28.1,漏电流IL=0.15μA。     

共沉淀法制备ZnO基纳米复合粉体及高压ZnO压敏电阻的电性能

以金属离子盐为原料,氨水、乙醇胺为沉淀剂,十二烷基苯磺酸钠、聚乙二醇2000为表面改性剂,采用共沉淀法制备ZnO基纳米复合粉体。以共沉淀法最佳工艺所得粉体制备高压ZnO压敏电阻。采用热重–差示扫描量热分析、X射线衍射、扫描电子显微镜、激光粒径分析对ZnO基复合前驱体及ZnO基纳米复合粉体进行表征,探讨了沉淀剂种类、溶液pH值、Zn2＋起始浓度和表面改性剂对粉体粒度的影响。结果表明：以氨水为沉淀剂、溶液体系pH值为6.0、Zn2＋浓度为1.0mol/L、聚乙二醇2000为表面改性剂时可制备出粒径分布窄、平均粒径为89nm的ZnO基复合粉体。用该粉体制备的高压ZnO压敏电阻的平均电位梯度为543V/mm,非线性系数为29.3,漏电流为49μA。通过共沉淀工艺,可制备出电性能优良的高压ZnO压敏电阻。     

High Nonlinearity and High Voltage Gradient ZnO Varistor Ceramics Tailored by Combining Ga2O3, Al2O3, and Y2O3 Dopants

This paper deals with the electrical characteristics of rare‐earth‐doped ZnO varistor ceramics. Multiple donor dopants (Al³⁺, Ga³⁺, and Y³⁺) were employed to improve the comprehensive performance of ZnO varistor ceramics. The leakage current of rare‐earth‐doped ZnO varistor ceramics decreased noticeably with Ga₂O₃ dopants. The Ga³⁺ dopant occupies the defect sites of grain boundaries and increases the barrier potential of ZnO varistor ceramics, so the leakage current is effectively inhibited. Y₂O₃ is primarily located around the grains, which restrains ZnO grain growth, increasing the voltage gradient. The Al³⁺ goes into the lattices of ZnO grains, decreasing the grain resistance; thus, the residual voltage ratio can be controlled at low levels under a high impulse current. With the combined incorporation of Al³⁺, Ga³⁺, and Y³, excellent electrical properties of ZnO varistor ceramics can be acquired with a nonlinearity coefficient of 87, voltage gradient of 517 V/mm, leakage current of 0.96 μA/cm², and residual voltage ratio of 1.60. These rare multiple donor dopants can aid in engineering high‐quality ZnO varistors.     

Simultaneously improving the electrical properties and long-term stability of ZnO varistor ceramics by reversely manipulating intrinsic point defects

Excellent electrical properties and the improved long-term stability of ZnO varistor ceramics were simultaneously achieved by doping NiO. The microstructural features were investigated using X-ray diffractometer, scanning electron microscopy, and energy dispersive spectroscopy, while the intrinsic point defects were characterized using frequency domain dielectric spectroscopy and verified by photoluminescence and Raman spectra. The results indicated that in the ZnO varistor ceramics, a reverse manipulation of donor point defects, i.e., suppressing mobile zinc interstitial but increasing stable oxygen vacancy, was achieved. The long-term stability of NiO-doped ZnO ceramics was improved via a decrease in zinc interstitial density, with a degradation rate of 0.064 μA cm^?2 h^?0.5. Meanwhile, due to an increase in oxygen vacancy density, the excellent nonlinear current–voltage performance, i.e., a high nonlinear coefficient (72.9), low leakage current density (0.08 μA cm^?2), and low grain resistivity (13.43 × 10^?3 Ω m), was maintained. The findings of this study provide a possible method for developing high-performance ZnO varistor ceramics by manipulating point defects.     

Microstructure and Crystal Phases of Praseodymium Oxides in Zinc Oxide Varistor Ceramics

The effect of sintering temperature on the microstructure and crystal phases of the intergranular praseodymium oxides in ZnO varistor ceramics was investigated using transmission electron microscopy and high-resolution electron microscopy. The ZnO grains were three-dimensionally separated from the intergranular praseodymium oxides. On the basis of microdiffraction analyses of the intergranular layer, the phase transformation from fcc-Pr₆O₁₁ into hcp-Pr₂O₃ was found when the sintering temperature increased from 1300° to 1350°C. The defect reaction equation and the decrease of donor concentration with increasing sintering temperature can verify the certainty of phase transition during the liquid-phase sintering observed by transmission elecron microscopy. Additionally, on the basis of the small variations of the breakdown voltage per grain boundary, the number of active grain boundaries is not a dominant factor for the donor concentration dependence on the sintering temperature.     

A novel economical grain boundary engineered ultra-high performance ZnO varistor with lesser dopants

A varistor having ultra-high performance was developed from doped ZnO nanopowders using a novel composition consisting of only three (Bi, Ca and Co oxides) dopants. Improved varistor properties were obtained (breakdown field (E_b) 27.5?±?5?kVcm^?1, coefficient of nonlinearity (α) 72?±?3 and leakage current density (L_c) 1.5?±?0.06?μAcm^?2) which are attributed to the small grain size and grain boundary engineering by phases such as Ca₄Bi₆O₁₃ and Ca_0.89Bi_3.11O_5.56 along with Co⁺² doping in the ZnO lattice. Complex impedance data indicated three relaxations at 25?°C and two relaxations at high temperature (>100?°C). The complex impedance data were fitted into two parallel RC model to extract electrical properties. Two stages of activation energy for DC conductivity were observed in these varistor samples where region I (<150?°C) is found to be due to shallow traps and region II (<225?°C) is due to deep traps. The novel composition is useful for commercial exploitation in wide range of surge protection applications.     

Effects of addition of chromium and/or nickel oxides on the electrical characteristics of yttrium oxide-doped high-voltage zinc oxide varistors

The effects of Cr₂O₃ and/or NiO addition to Y₂O₃-doped Bi-based high-voltage ZnO varistors were investigated, including crystal structure and interface states analysis. Incorporating 0.35 mol% Cr₂O₃ in Y-doped varistors increased the single-grain varistor voltage V_NNGB from 2.6 to 3.3 V and decreased the leakage current density by a factor of 40, from 2 × 10^?5 to 5 × 10^-7 A/cm². The nonlinearity index α before and after degradation increased from 21 to 35. 1.2 mol% NiO increased V_NNGB to 4 V. Highest varistor voltage was 1500 V for 0.3 mol% NiO. Resistance to electrical degradation improved with optimal amounts of Cr or Ni by reduction of grain boundary oxygen vacancies. Though the donor density was changed prominently by addition of Cr and/or Ni, changes in the barrier height were suppressed by the change in interface state density. As a result, the change in V_NNGB was related mainly to the empty interface state under no bias.