烧结工艺对ZnO压敏陶瓷微观结构与电学性能影响

以ZnO粉末为主要原料,添加TiO2、Bi2O3、MnO2、Co2O3、Sb2O3为组元,在不同烧结温度(1100~1250℃)与保温时间(1.0~2.5h)下制备ZnO压敏陶瓷。采用SEM观察陶瓷形貌,利用压敏电阻直流参数仪测试陶瓷的电学性能,研究烧结温度与保温时间对陶瓷结构和性能的影响。结果表明,随烧结温度升高,压敏电压、漏电流逐渐降低,而非线性系数先减小后增加。制备ZnO压敏陶瓷的适宜烧结温度与保温时间分别为1250℃、1h,压敏电压为17.0V/mm、漏电流为0.014mA、非线性系数为14.2,陶瓷内部晶粒可长大至128.7μm。     

Li2O为烧结助剂的Si3N4陶瓷低温烧结过程研究

分别选用Li2O烧结助剂和Y2O3-Al2O3复合烧结助剂作为对比,无压烧结氮化硅陶瓷,研究了Li2O对烧结致密化过程和相变过程的影响。结果表明,以Li2O作为烧结助剂,烧结系统的共晶液相在1200℃产生,颗粒重排可以在较低的温度下进行,且致密化速度较快,氮化硅的α-β相变过程被促进,在1600oC即可得到发育良好的β-Si3N4棒状晶。     

合成工艺对CaCu3Ti4O12陶瓷介电性能的影响（英文）

利用溶胶凝胶工艺制备CaCu3Ti4O12粉体,经相同压力和时间冷压后,于1000℃下进行烧结,制备CaCu3Ti4O12陶瓷。微观组织观察表明,烧结时间对复合陶瓷的晶粒尺寸有显著的影响;烧结不同时间的复合陶瓷的介电常数和介电损耗在50Hz到100kHz的范围内表现出弱的频率相关性。随着频率的增加,复合材料的介电损耗降低,而介电常数保持在一个较高值。最佳的烧结时间为6h。     

稀土Pr6O11掺杂水平对ZnO-Pr6O11-Co3O4-TiO2压敏电阻材料的微观结构和电学性能的影响

通过传统陶瓷工艺,在1350℃下烧结得到了不同稀土Pr6O11掺杂水平的ZnO-Pr6O11-Co3O4-TiO2压敏电阻材料,研究了Pr6O11掺杂水平对压敏电阻材料微观结构和电学性能的影响。结果表明:随着Pr6O11掺杂水平的变化,样品相组成没有发生变化,样品由ZnO、Pr6O11、Zn2TiO4和PrTiO34种相组成;Pr6O11掺杂既能促进样品烧结致密,还可抑制ZnO晶粒的生长;在Pr6O11掺杂量不超过2.0mol%时,Pr6O11掺杂水平提高可提高样品压敏电压,在Pr6O11掺杂量不超过1.5mol%时,Pr6O11掺杂水平提高可提高样品非线性系数,降低漏电流。     

烧结温度对CaCu3Ti4O12陶瓷C波段介电性能的影响

采用固相反应法制备了CaCu3Ti4O12(CCTO)陶瓷,研究了烧结温度对CCTO晶相、微观形貌、致密度以及在C波段(3.95～5.85 GHz)的介电性能的影响。结果表明,在1040℃烧结的试样除了含有CCTO,还存在部分没有反应的TiO2。随着烧结温度的升高,TiO2逐渐消失。与1040℃和1060℃烧结的试样相比,在1080℃烧结的试样晶粒尺寸较大且粒径较均匀,而在1100℃烧结的试样有明显的熔化现象。试样的密度随烧结温度的升高而增加,在1080℃时达到最大值。在1040～1080℃烧结的试样,其介电常数随着烧结温度的升高而增加,而在1100℃烧结的试样的介电常数反而有所降低。不同烧结温度下的CCTO陶瓷的介电常数和介电损耗随频率的增大变化不大。在所得的试样中,在1080℃烧结的CCTO陶瓷介电常数最高,介电损耗最低。     

烧结温度对WO_3系电容-压敏复合陶瓷电性能的影响(英文)

研究了烧结温度对WO_3系电容-压敏复合陶瓷显微结构、非线性电学性能及介电性能的影响.随着烧结温度从1050 ℃到1200 ℃的升高,WO_3陶瓷的晶粒尺寸增大,压敏电压随之降低.在1150 ℃烧结条件下,掺杂0.8 mol% Y_2O_3 的WO_3 压敏陶瓷样品表现出优良的综合电性能,其非线性系数为3.5,相对介电常数为1.13×10~4.然而,过高的烧结温度,不利于样品的非线性电学性能.WO_3系电容-压敏复合陶瓷较适合的烧结温度为1150 ℃,这是因为,在此温度下最有利于样品的晶界势垒结构的形成.     

Mn掺杂In2O3陶瓷材料的高温热电传输性能

利用放电等离子(SPS)烧结工艺制备Mn掺杂In2O3多晶陶瓷材料。通过测试热电传输性和观察微观结构,研究了掺杂工艺对SPS烧结多孔结构In2O3陶瓷传输性能的影响。结果表明,低浓度掺杂的样品在测试温度范围内能得到较高的电导率和热电势;掺杂试样In1.99Mn0.01O3在973 K可获得最高的热电功率因子4.0×10-4W.K-2.m-1,从而可知,控制In2O3中低浓度的Mn的掺杂量可获得较好的高温n型热电材料。     

AI2O3/Cu复合材料制备工艺的优化

新型颗粒增强铜基复合电极材料Al2O3/Cu能较好地解决电阻点焊镀锌钢板时普通电极材料做电极寿命较短的问题。为了获得优化的Al2O3/Cu复合电极材料制备工艺,采用粉末冶金法制备Al2O3/Cu复合电极材料,通过改变制备过程中的工艺参数,以密度、显微维氏硬度、电导率、显微组织为检测内容,探讨压制力和烧结温度对Al2O3/Cu复合电极材料物理机械性能和显微组织的影响。结果表明,综合性能最优时的Al2O3/Cu复合电极材料制备工艺为:Cu-Al2O3混合粉末制坯压制力100 kN,烧结温度940℃。     

Y2O3对反应烧结Si3N4/SiC复相陶瓷组织和性能的影响

以低压铸造用升液管为研究目的,以Y2O3-Al2O3-Fe2O3为复合烧结助剂,磨切单晶硅废料Si粉和SiC为主料,反应烧结法制备Si3N4/SiC复相陶瓷。研究了Y2O3含量对复合材料结构和力学性能的影响,采用XRD、SEM对复合材料的相组成、微观形貌进行分析。结果表明,反应烧结后试样生成Si3N4结合SiC晶粒为主相的烧结体,并含有少量Sialon晶须及未反应的Si。Y2O3含量对复相陶瓷力学性能影响很大,在分析稀土Y2O3作用机理的基础上,得到2.5%Y2O3优化试样的力学性能优良,相对密度达到88%,维氏硬度达到1.1 GPa,常温抗弯强度50 MPa。     

Fe/Al2O3复合材料的还原制备及其表征

金属陶瓷复合材料是由金属或合金与陶瓷相组成的非均质复合材料。由于金属和陶瓷的电导率、磁导率具有较大的差异,金属陶瓷复合材料表现出独特的电磁性能。以Al2O3和Fe2O3粉体为原料,通过高能球磨、无压烧结和选择性还原工艺,成功制备出不同组分的Fe/Al2O3复合材料,利用XRD、SEM对复合材料的物相组成及微观形貌进行分析和观察。结果表明:还原后样品的主晶相为(FexAl1-x)2O3固溶体和Fe3O4,并且出现了亚微米级粒度的Fe颗粒。利用阻抗分析仪对样品的介电性能的研究(测试频率为10MHz～1GHz)表明,材料的介电常数实部和虚部均随着频率增加而下降,并且随着原料中Fe2O3含量的增加而呈上升的趋势,这种介电常数增大的现象主要由界面极化引起。     

The effect of calcining temperatures on the phase purity and electric properties of CaCu3Ti4O12 ceramics

CaCu₃Ti₄O₁₂ (CCTO) ceramics are prepared by the traditional solid-state reaction method under the same sintering conditions. The effect of calcining temperatures for the powders before sintering on the microstructure and electric properties of CCTO ceramics has been investigated. The XRD patterns for the powder calcined at 950 °C show that some measure of second phases (CaTiO₃, TiO₂ and CuO) can be found except a considerable amount of CCTO phase in them and the content of second phases decrease markedly as the calcining temperature is raised to 1000 °C. The XRD patterns for the powder calcined at 1050 °C indicate that the powder has been basically formed into a single CCTO phase except a small quantity of CaTiO₃ phase, which is attributed to CuO volatilizing in the calcining process. Furthermore, the XRD patterns for the CCTO pellets sintered at 1080 °C/10 h manifest that all the second phases have disappeared after the sintering process except that a very weak peak of CaTiO₃ can still be seen in the XRD pattern for the pellets made of the powder calcined at 1050 °C. The electric properties measurement demonstrates that the lower calcining temperature for the raw powder is helpful to increase the values of permittivity and the higher calcining temperature is helpful to improve the non-ohmic properties. The non-ohmic characteristic has a behavior reverse to that of the permittivity, which can be ascribed to the change in the height of Schottky barriers.     

Li2CO3掺杂BaTiO3无铅压电陶瓷的低温烧结

以Li2CO3作为烧结助剂,采用传统固相烧结法制备BaTiO3陶瓷。研究了烧结温度(1000~1150℃)和Li2CO3添加质量分数(0%~5%)对BaTiO3陶瓷结构和电学性能的影响。结果表明:Li2CO3的掺入有效地促进了陶瓷的烧结,使BaTiO3的烧结温度从1300℃以上降低到1050℃。X射线衍射结果表明:未掺Li2CO3的BaTiO3陶瓷样品为四方相结构,掺Li2CO3的BaTiO3陶瓷样品为正交相结构。Li2CO3掺量为1%的陶瓷样品具有较高的致密度,且在1050℃时获得最大值,其相对密度可达94%。当烧结温度为1100℃时,BaTiO3陶瓷的压电常数d33获得最大值,且d33随着Li2CO3掺量的增加而降低。其中Li2CO3掺量为1%时陶瓷具有较好的电性能:d33=200pC/N,εr=1322,TC=115℃。     

烧结温度对0.9PbZr0.52Ti0.48O3-0.1NaNbO3压电陶瓷结构及电学性能的影响

采用传统固相烧结法制备了钠过量的0.9PbZr0.52Ti0.48O3-0.1NaNbO3(PZT-NN)压电陶瓷,研究了烧结温度对PZT-NN陶瓷晶体结构及其电学性能的影响。XRD结果表明,不同温度烧结的PZT-NN陶瓷均为单一钙钛矿结构,在1125~1150℃温区烧结时,陶瓷发生了由四方相向正交相的相变。随烧结温度进一步升高,压电常数d33、介电常数εr以及剩余极化强度Pr均呈递减趋势,烧结温度为1125℃的PZT-NN陶瓷具有较好的电学性能:d33=218pC/N,εr=851,tanδ=0.02。PZT-NN陶瓷的相对密度随烧结温度的升高而增大,在1150℃时达到95%,钠过量的NaNbO3加入使PZT陶瓷的致密化烧结温度降低了50~150℃。     

An aqueous-solution based low-temperature pathway to synthesize giant dielectric CaCu3Ti4O12—Highly porous ceramic matrix and submicron sized powder

A simple, cost-effective and environment-friendly pathway for preparing highly porous matrix of giant dielectric material CaCu₃Ti₄O₁₂ (CCTO) through combustion of a completely aqueous precursor solution is presented. The pathway yields phase-pure and impurity-less CCTO ceramic at an ultra-low temperature (700 °C) and is better than traditional solid-state reaction schemes which fail to produce pure phase at as high temperature as 1000 °C (Li, Schwartz, Phys. Rev. B 75, 012104). The porous ceramic matrix on grinding produced CCTO powder having particle size in submicron order with an average size 300 nm. On sintering at 1050 °C for 5 h the powder shows high dielectric constants (>10⁴ at all frequencies from 100 Hz to 100 kHz) and low loss (with 0.05 as the lowest value) which is suitable for device applications. The reaction pathway is expected to be extended to prepare other multifunctional complex perovskite materials.     

Dielectric relaxation behaviors of pure and Pr6O11-doped CaCu3Ti4O12 ceramics in high temperature range

Pure and Pr₆O₁₁-doped CaCu₃Ti₄O₁₂ (CCTO) ceramics were prepared by conventional solid-state reaction method. The compositions and structures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of Pr-ion concentration on dielectric properties of CCTO were measured in the ranges of 60 Hz-3 MHz and 290-490 K. The third phase of Ca₂CuO₃ was observed from the XRD of CCTO ceramics. From SEM, the grain size was decreased obviously with high valence Pr-ion (mixing valence of Pr³⁺ and Pr⁴⁺) substituting Ca²⁺. The room temperature dielectric constant of Pr-doped CCTO ceramics, sintered at 1323 K, was an order of magnitude lower than the pure CCTO ceramics due to the grain size decreasing and Schottky potential increasing. The dielectric spectra of Pr-doped CCTO were flatter than that of pure CCTO. The loss tangent of Pr-doped CCTO ceramics was less than 0.20 in 2 × 10²-10⁵ Hz region below 440 K. The complex impedance spectra of pure and Pr-doped CCTOs were fitted by ZView. From low to high frequency, three semicircles were observed corresponding to three different conducting regions: electrode interface, grain boundary and grain. By fitting the resistors R and capacitors C, the activation energies of grain boundary and electrode contact were calculated. All doped CCTOs showed higher activation energies of grain boundary and electrode than those of pure CCTO ceramics, which were concordant with the decreasing of dielectric constant after Pr₆O₁₁ doping.     

退火温度对纳米晶Ni_(0.5)Zn_(0.5)Fe_2O_4吸波性能的影响

采用溶胶-凝胶自燃烧法制备了Ni_(0.5)Zn_(0.5)Fe_2O_4纳米晶,将其分别在550、800和1050℃下二次退火2h,利用XRD和微波矢量网络分析方法对二次热处理产物及其电磁性质进行了研究.结果表明,自燃烧后已形成完整的结晶尖晶石型Ni_(0.5)Zn_(0.5)Fe_2O_4纳米晶.在0.1～1.5 GHz的测试频率,纳米晶具有介电损耗和磁损耗,且随着热处理温度的升高,电损耗逐渐减小.在1050℃下退火后获得的Ni_(0.5)Zn_(0.5)Fe_2O_4纳米晶材料的μ'、μ"以及磁损耗正切tanδ_m明显大于在室温及550、800℃退火后的试样,在所测频率内具有优异的磁吸收性能.     

添加KNN和BBS对BaTiO3陶瓷微结构和介电性能的影响

采用固相法制备添加K0.5Na0.5NbO3(KNN)和BBS玻璃(BBS)的BaTiO3电容器陶瓷。借助X射线衍射仪、扫描电镜和阻抗分析仪研究掺杂对晶体结构、微观组织及介电性能的影响。结果表明:单独添加KNN的样品呈单一的钙钛矿结构。随KNN的增加,陶瓷样品高温端的电容变化率减小。掺杂3%~5%KNN(摩尔分数)陶瓷满足X7R特性。掺杂1%BBS(质量分数)对含3%KNN(摩尔分数)陶瓷的晶体结构无影响。BBS超过3%(质量分数)时,有第二相Bi4B2O9和BaTi5O11生成。1 100℃烧结掺杂3%BBS(质量分数)和1%KNN(摩尔分数)的BaTiO3陶瓷具有中等介电常数(1 045),低的介电损耗(0.74%)和较高的体积电阻率(5.5×1011.cm),在55、125和150℃的电容变化率分别为6.6%、1.7%和13.2%,有望用于中温制备的X8R型多层陶瓷电容器。     

Microstructures and electrical responses of pure and chromium-doped CaCu3Ti4O12 ceramics

Pure and chromium-doped CCTO (CaCu₃Ti₄O₁₂) ceramics were prepared by a conventional solid-state reaction method, and the effects of chromium doping on the microstructures and electrical properties of these ceramics were investigated. Efficient crystalline phase formation accompanied by dopant-induced lattice constant expansion was confirmed through X-ray diffraction studies. Scanning electron microscopy (SEM) results show that doping effectively enhanced grain growth or densification, which should increase the complex permittivity. The dielectric constant reached a value as high as 20,000 (at 1 kHz) at a chromium-doping concentration of 3%. The electrical relaxation and dc conductivity of the pure and chromium-doped CCTO ceramics were measured in the 300-500 K temperature range, and the electrical data were analyzed in the framework of the dielectric as well as the electric modulus formalisms. The obtained activation energy associated with the electrical relaxation, determined from the electric modulus spectra, was 0.50-0.60 eV, which was very close to the value of the activation energy for dc conductivity (0.50 ± 0.05 eV). These results suggest that the movement of oxygen vacancies at the grain boundaries is responsible for both the conduction and relaxation processes. The short-range hopping of oxygen vacancies as “polarons” is similar to the reorientation of the dipole and leads to dielectric relaxation. The proposed explanation of the electric properties of pure and chromium-doped CCTO ceramics is supported by the data from the impedance spectrum.     

CaCu_3Ti_4O_(12)陶瓷的巨介电响应机理

针对CaCu3Ti4O12(CCTO)陶瓷的巨介电性起源存在较大争议的情况,以少量MnO2取代CCTO中CuO或TiO2、采用固相反应法烧结制备名义成分为CaCu3-xMnxTi4O12(x=0~0.3)和CaCu3Ti4-yMnyO12(y=0~0.1)的陶瓷。通过微结构和电性能的演变讨论CCTO陶瓷的巨介电响应机理。结果表明:加入少量MnO2后,所有陶瓷均为体心立方(BCC)类钙钛矿结构的CCTO单相;但是,CCTO陶瓷显微结构从异常长大的晶粒转变成均匀的细小晶粒;同时,CCTO陶瓷的电阻率从107-.cm显著提高到109-.cm;介电常数从104显著下降到102;介电损耗从10-1急剧降低到10-3;CCTO陶瓷的巨介电响应是由半导体化的晶界/亚晶界和相对绝缘的晶粒/亚晶粒组成的内部阻挡层电容器(IBLC)所致。在较低温度下(<1 100℃)烧结获得高介电常数、低损耗和温度稳定的CCTO基陶瓷,找到一种降低CCTO陶瓷介电损耗的有效方法。