【作者】 赵晨；

【导师】 黄新友；

【作者基本信息】 江苏大学 ， 材料学， 2007， 硕士

【摘要】 本文对近年来钛酸锶钡制备技术进行了全面综述。研究了稀土氧化物（Dy₂O₃、CeO₂、La₂O₃、Y₂O₃和Vb₂O₃等）以及MgO、Bi₄Ti₃O₁₂和Bi₂Sn₂O₇等组分对钛酸锶钡电容器陶瓷介电性能和结构的影响，得到了致密度高、气孔率小，晶粒细小均匀且耐压强度较高符合X7R特性的电容器陶瓷。并且研究了制备工艺参数的影响，利用扫描电镜（SEM），X射线衍射分析（XRD）等检测方法对材料的物相组成、显微结构等进行了研究。以此为依据探讨了掺杂物改性的作用机理。本研究主要结果如下：在钛酸锶钡基陶瓷中微量掺杂稀土氧化物Dy₂O₃和Y₂O₃可以抑制晶粒生长，产生细晶效应，使得居里峰在整个工作温区内弥散展宽，获得较高的介电常数和良好的容量温度特性，并可以大幅度提高钛酸钡基陶瓷的耐压强度。1250℃烧结含0.6wt％Y₂O₃的钛酸锶钡陶瓷，其ε≥4000，在-25～80℃范围内，ΔC／C≤20％，击穿场强E≥6kV／mm。CeO₂和La₂O₃掺杂的结果表明这两种稀土元素对钛酸锶钡陶瓷的晶粒生长有一定的抑制作用。CeO₂的掺杂量在0.9％，La₂O₃的掺杂量在0.45％（质量分数）左右对钛酸锶钡陶瓷陶瓷的介电性能有很好的改善作用。但是镧离子和铈离子在陶瓷中的离子取代情况有所不同。因而，改善性能的作用不同。CeO₂掺杂的陶瓷性能优于La₂O₃掺杂的陶瓷。1250℃烧结含0.9wt％CeO₂的钛酸锶钡陶瓷，其ε≤3000，在-25～80℃范围内，ΔC／C≤35％，击穿场强E≥4kV／mm。Yb₂O₃的加入没有改变BST陶瓷的晶体结构。随着保温时间的增加，陶瓷的介电常数增大。1250℃烧结含1.2wt％Yb₂O₃的钛酸锶钡陶瓷，其ε≥10000，击穿场强E≥7kV／mm。MgO掺杂后的样品的介电峰被压抑和展宽，表现出扩散相变。从XRD谱图可知，MgO样品仍为单一的钙钛矿结构。1250℃烧结含0.2wt％MgO的钛酸锶钡陶瓷，其ε≥4500，在-25～80℃范围内，ΔC／C≤25％，击穿场强E≥6.5kV／mm。研究表明，Bi₄Ti₃O₁₂、Bi₂Sn₂O₇两种掺杂物包裹晶粒和填充晶粒间，构成瓷体的复杂非均匀结构。这两种异相对（Ba，Sr）TiO₃铁电相有制约作用，使B位阳离子所处的势阱深度变浅，在宽广的温度范围内极化易被电场所定向，表现为ε-T特性曲线较平坦。1150℃烧结含30wt％Bi₂Sn₂O₇的钛酸锶钡陶瓷，其ε≥1500，在-55～125℃范围内，ΔC／C≤15％。研究了Ba／Sr比对BST陶瓷性能的影响。研究表明：钡锶比对陶瓷的介电性能的改善是至关重要的。通过研究配方和工艺，得到了高介电常数、低容温变化率的高压电容器瓷料。其主要性能指标为：烧结温度为1250℃，ε≥3500，tgδ≤0.01，在-25～80℃范围内，ΔC／C≤15％，试样击穿强度E≥5.5kV／mm。更多还原

【Abstract】 In this article the barium-strontium titante preparation techniques in recent yearshave been summarized. The results of rare-earth oxide（such as Dy₂O₃、CeO₂、La₂O₃、Y₂O₃ and Yb₂O₃ etc.）, and the additions of MgO、Bi₄Ti₃O₁₂ and Bi₂Sn₂O₇ on dielectricproperties and microstructure are studied. The results show that the samples with highdensity, low pore rate and close homogeneous grain possess the high electric breakdownstrength and suited for X7R character. The influences of technological parameter on theceramic properties have been investigated. Moreover, with the aids of SEM and XRD,the samples are analysed, and the results are used to discuss the machanism ofimproving characteristics.The following experiment results have been achieved:In barium-strontium titanate based ceramic, doping small rare earth oxide Dy₂O₃and Y₂O₃ can keep back the growth of crystal grain, producing close grain effect,making curie summit in entire work temperature range scatter and spread, get higherdielectric constant and good capacity temperature property, raising the compressionstrength of barium-strontium titanate based ceramic substantially. When the content ofY in barium-strontium titanate ceramics is O.6wt% sintering at 1250℃, relativedielectric constant is more than 4000; from-25 up to 80℃, the change of temperaturedependence of relative permittivity is less than 20%; electric breakdown strength E ismore than 6kV/mm.In barium-strontium titanate based ceramic, doping small rare earth oxide CeO₂and La₂O₃ can inhibit the grain growth and reduce the size of grain, and the dielectricperprities of barium-strontium titanate ceramics can be improved by adding properamount of La³⁺ and Ce⁴⁺ dopants. But replacement mechanism of Ce⁴⁺ and La³⁺ forbarium-strontium titanate is different. Dielectric perproties of Ce-doped BST ceramicsis better than that of La-doped. When the content of Ce⁴⁺ in barium-strontium titanateceramics is O.9wt% sintering at 1250℃, relative dielectric constant is more than 3000;from-25 up to 80℃, the change of temperature dependence of relative permittivity isless than 35%; electric breakdown strength E is more than 4kV/mm.X-ray diffraction analysis shows that the crystal structure of barium-strontiumtitanate ceramics is not affected by Yb-doping. With the increase of sinteringtemperature, the dielectric constants of barium-strontium titanate ceramics becomeelevation. When the content of Yb³⁺ in barium-strontium titanate ceramics is 0．9wt% sintering at 1250℃, relative dielectric constant is more than 10000; electric breakdownstrength E is more than 7kV/mm.The temperature dependence of dielectric constant is depressed and broadens withMgO doped. And XRD paterns show a single perovskite phase on samples. When thecontent of Mg²⁺ in barium-strontium titanate ceramics is 0．2wt% sintering at 1250℃,relative dielectric constant is more than 4500; from-25 up to 80℃, the change oftemperature dependence of relative permittivity is less than 25%; electric breakdownstrength E is more than 6．5kV/mm.The results show that Bi₄Ti₃O₁₂ and Bi₂Sn₂O₇ parcel crystal grain and are filledwith between grains, forming the complex and not even structure of ceramic body.Different phases restricts barium-strontium titanate ferroelectric phases, making thedepth of potential well of B position cation change shallow. In the broad temperaturescope, polarization is easily located by electric field, which showε-T characteristiccurve rather smooth. When the content of Bi₂Sn₂O₇ in barium-strontium titanateceramics is 30wt% sintering at 1150℃, relative dielectric constant is more than 1500;from-55 up to 125℃, the change of temperature dependence of relative permittivity isless than 15%.The results of Ba/Sr ratio on dielectric properties and microstructure are studied.The results show the optimized matching of Ba/Sr ratio is very important to dielectricperproties of BST ceramics.A kind of perfect ceramic material for capacitors is obtained by the selections ofdopants and processing. Its main electrical performances are:ε≥3500; tgδ≤0．01; from-25 up to 80℃, the change of temperature dependence of relative permittivity is lessthan 15%; electric breakdown strength E is more than 5．5kV/mm.更多还原