来源：高电位梯度氧化锌压敏陶瓷的制备、显微组织结构及电性能研究 发布时间：2010年7月20日
本文通过高能球磨法获得ZnO压敏纳米粉料，细致研究800-1000℃烧结条件下，高能球磨和掺杂稀土氧化物Y2O3、Dy2O3、Er2O3提高电性能的机理，首次在1000℃低温烧结，制备出电位梯度超过400V／mm、通流能力大于230J／cm3，残压比小于1.65的高性能ZnO压敏陶瓷。 首先研究了烧结温度及球磨时间对高能球磨压敏陶瓷的电性能、致密度及显微组织结构的影响；球磨时间对粉料粒度和结构的影响以及钢球对粉料的污染程度。研究结果表明，随烧结温度提高，压敏陶瓷电位梯度、非线性系数及致密度逐渐降低降低，而漏电流逐渐升高。富铋相逐渐蒸发减少或消失，导致致密度降低，这也是高温烧结区间(1100-1300℃)非线性系数陡然降低和漏电流骤然升高的根本原因。高能球磨使晶格发生严重畸变，大半径离子在ZnO晶粒内固溶量增加，使样品势垒高度(ΦB)、施主浓度(Nd)及界面态密度(Ns)增加，势垒宽度(ω)降低，因而改善了电性能。随高能球磨时间延长，效果愈显著。压敏陶瓷致密度随球磨时间的增加而升高，主要是由于高能球磨细化了晶粒尺寸，使晶格畸变能增加，显著提高了烧结驱动力和烧结动力学因子，缩短了反应扩散距离；烧结出现的液相增加了反应相间的接触面积，加速了传质速度，促进了相间反应。高能球磨引起的压敏陶瓷晶粒细化主要发生在0-5小时阶段且烧结温度越低，效果越明显。高能球磨5h后，粉料颗粒尺寸由1.50μm减小到0.42μm并发生聚集，显著增强了粉末的烧结性。20h高能球磨后，粉料ZnO平均晶粒尺寸由120nm减少至59nm。高能球磨后，粉料衍射峰明显宽化，但未发生相变。在本文试验条件下，钢球Fe元素污染对电性能不会造成危害。 为了提高压敏电位梯度及改善综合性能，系统地研究了高能球磨并低温烧结下，掺杂稀土氧化物Y2O3、Dy2O3、Er2O3对ZnO压敏陶瓷性能的影响机理。 ZnO压敏陶瓷加入Y2O3后，电位梯度有显著提高，温度越低，提高的效果越明显。随Y2O3含量的增加，电位梯度逐渐增大；非线性系数呈升高趋势；漏电流比未加Y2O3的漏电流低，且随Y2O3含量的增加，漏电流降低平缓；900-1000℃试样致密度大于未加Y2O3的，且随着Y2O3含量增加，致密度增大，800℃试样致密度呈连续降低趋势。综合考虑压敏陶瓷的电性能指标及致密度因素，800℃烧成的掺有Y2O3压敏陶瓷的综合性能最好。掺杂Y2O3的ZnO压敏陶瓷在800℃烧结时，结构出现四相，即ZnO、γ-Bi2O3、Zn2.33Sb0.67O4及Y2O3相。Y2O3相存在于ZnO晶界上，阻止了ZnO晶粒的长大。随Y2O3含量的增加，ZnO晶【Abstract】 The influence of high-energy ball milling (HEBM) and rare-earth oxide of Y_2O_3, Dy_2O_3 and Er_2O_3 on the electrical properties of ZnO-based varistor ceramics sintered at 800-1000℃ was researched. Using nanocrystalline ZnO-based varistor powders obtained by HEBM, advanced ZnO-based varistor ceramics sintered at 1000℃, with voltage gradient above 400V/mm, energy absorption more than 230J/cm3 and residual voltage ratio less than 1.65, were made the first time.The influence of sintering temperature and ball milling tune on the electrical properties, density and microstructures of high-energy ball milled varistor ceramics, and the influence of ball milling time on powder particle size, structure and the contamination from steel balls, were researched firstly. The results showed that the varistor ceramics' voltage gradient, nonlinear coefficient and density decreased and leakage current increased with increasing sintering temperature. Very little Bi-rich phase or vanishment resulted from vaporizing leads to the decrease in density, the steep decrease in nonlinear coefficient and the rapid increase in leakage current when samples sintered at 1100-1300℃. HEBM made a severe lattice distortion, following that the large-radius ions' solubility increased within ZnO grain and barrier height (Φ_b), donor concentration (N_d), density of interface states (N_s) increased and barrier width( ω )decreased, and hence the electrical properties were improved. With the time of HEBM increasing, this effect becomes more notable. Varistor ceramic density increasing with increasing ball milling time comes mainly from two reasons. First, HEBM caused the refinement of the grain sizes and enhanced lattice distortion energy in the powders, which are responsible for the increase in the sintering driving force and kinetics factor and the shortening of the elemental diffusion distance. Second, liquid phases increased the contacted area between reactant phases, accelerated the transmission speed, promoted the reaction among reactant phases. The refinement of the grain size caused by HEBM is prominent at the stage of milling for 0-5h and this effect becomes more distinct with decreasing sintering temperature. Particle size was reduced from 1.50 to 0.42μm after HEBM for 5h, enhancing the sinterability of mixed powders. Average ZnO grain size was reduced from 120 to 59 run after HEBM for 20h. Phase transformation did not generate after HEBM, but diffraction peaks were very wide. The Fe contamination from steel balls is not detrimental under our