不同化学组分对CaCu3Ti4O12介电陶瓷性能的影响

用溶胶-凝胶（Sol-gel）技术制备了掺杂5％、10％的Ca、Cu及Ti化学组分的化合物CaCu3Ti4O12系列纳米粉体并后续烧结成多晶陶瓷。用XRD、SEM手段表征了烧结体的晶相和微观形貌。通过研究样品的介电性能，发现系列金属离子的掺杂几乎没有改善样品的介电性能。实验研究表明，经1000℃烧结、保温2h严格按照化学组分配制的CaCu3Ti4O12介电陶瓷的致密性好、晶粒均匀，具有良好的介电性能，室温下在10^2～10^5Hz宽频范围，介电常数ε达到～10^4，介电损耗低于～0.15。     

CaCu3Ti4-3/4zFezO12/偏聚氟乙烯和Ca1-3/2xLaxCu3-yMgyTi4O12/偏聚氟乙烯复合材料的制备及介电性能研究

以CaCu3Ti4O12为原料,采用溶胶-凝胶法制备CaCu3Ti4-3/4zFezO12 (CCTFO)和Ca1-3/2xLaxCu3-y MgyTi4O12(CLCMTO)前驱粉体,以聚偏氟乙烯(PVDF)为基体采用球磨共混法热压制备CaCu3Ti4-3/4zFezO12(CCTFO)/PVDF和Ca1-3/2xLaxCu3-yMgyTi4O12(CLCMTO)/PVDF复合材料,考察掺杂量和前驱粉体填充质量对复合材料微观结构和介电性能的影响。结果表明:当前驱粉体填充质量增加到50%时,复合材料出现团聚现象。复合材料的介电常数和介电损耗均随填料含量的增加而升高,Fe掺杂后虽然不能提高复合材料的介电常数,但能降低中到高频段的介电损耗,La、Mg双掺杂不仅可以提高介电常数还可以降低介电损耗。     

溶胶-凝胶法引入ZnO-2B2O3-7SiO2玻璃对BaO-Sm2O3-4TiO2陶瓷性能的影响

采用固相反应法合成BaO-Sm2O3-4TiO2 (BST)陶瓷粉体.系统研究了溶胶-凝胶法引入ZnO-2B2O3-7SiO2 (ZBS)玻璃对BST陶瓷烧结特性、物相组成、微观形貌及介电性能的影响.结果表明,添加ZBS玻璃的陶瓷试样主晶相仍为类钙铁矿钨青铜结构的BaSm2Ti4O12,次晶相为Sm2Ti2O7.通过溶胶-凝胶法添加6％(质量分数)的ZBS玻璃,可使BST陶瓷的烧结温度从1350℃降低到1050℃,在1050℃烧结3h所得BST陶瓷介电性能优良:εr=60.17,tanδ=0.004,τf=-7.9×10 6/℃.     

Sol-gel自蔓延燃烧制备CaCu3Ti4O12纳米粉体及其介电性能研究

以硝酸钙、硝酸铜、钛酸四丁酯、冰乙酸和无水乙醇为原料,采用溶胶-凝胶自蔓延燃烧反应成功地制备了平均粒径为60～80nm的CaCu3Ti4O12纳米粉体.采用XRD、TEM和IR对纳米粉体的结构、形貌和光谱特性进行了分析和表征,并借助TG-DSC研究了干凝胶的自蔓延特性和晶化过程.采用传统烧结工艺制备了陶瓷,测得其在室温、lkHz时的介电常数为6×104.     

BaTiO3纳米粉体的制备和性能

采用溶胶-凝胶和溶胶-沉淀的方法合成了立方相纳米BaTiO3粉体．溶胶-凝胶法制备的粉体平均粒径为19nm，颗粒分布均匀、含少量BaCO3．溶胶-沉淀法得到了纯BaTiO3粉，平均粒径为42nm，存在部分团聚．两种方法相比，溶胶-凝胶法的粉体烧结密度较高，介电性能较好．讨论了两种合成方法的晶粒形成机理及对材料微观结构和介电性能的影响．     

溶胶-凝胶制备（Ca0．7Mg0．3）SiO3陶瓷及其微波介电性能

以硝酸钙、硝酸镁、正硅酸乙酯为先驱体,利用溶胶-凝胶法合成了(Ca0.7Mg0.3)SiO3陶瓷粉体,研究了不同物相和粒径粉体的烧结特性以及陶瓷的微波介电性能.结果表明:干凝胶的煅烧温度低于800°C时,所得粉体士要为尢定型态,煅烧温度超过900°C后,晶相大量形成;当以无定型粉体或900°C煅烧获得的细小粒径粉体为原料时,均难以获得致密结构的陶瓷;形成完整的粉体原料晶相以及粒径的增大,有利于陶瓷体的致密烧结和微波介电性能的提高.粒径分别为50～100nm以及90～300nm的陶瓷粉体,在1320°C烧结后均获得良好的微波介电性能,介电常数Er分别为6.62、6.71,品质因数Q Xf值分别为36962、41842GHz,谐振频率温度系数Tf分别为-48.32 × 106°C、49.63×106/°C.     

CaCu2.7Ti4O12介电性能和J-E特征

采用传统的固相反应法制备了Cu欠量的CaCu3Ti4O12(CaCu2.7Ti4O12)陶瓷,研究了不同烧结时间对CaCu2.7Ti4O12相结构、显微形貌、介电性能和J-E非线性特征的影响。结果表明,延长保温时间降低了CaCu2.7-Ti4O12陶瓷的中低频介电损耗和击穿场强并且显著提高了其介电常数。采用肖特基热电子发射模型对其非线性特征和电学性能的变化机理进行了分析,认为耗尽层宽度是影响电学性能的主要因素。保温30h的CaCu2.7Ti4O12陶瓷有望作为低压压敏电阻应用于半导体电路中。     

溶胶-凝胶法制备纳米PZT粉体及结构表征

采用改进的溶胶-凝胶法,以乙二醇为溶剂,硝酸锆为锆源,制备了纳米Pb(Zr0.52Ti0.48)O3粉体.通过溶胶的红外光谱分析给出了溶胶、凝胶形成的机理.通过IR,TG-DTA,XRD,SEM,TEM分析对PZT纳米晶的生长过程及性能进行了表征.实验证明:在650℃热处理2h,获得较完整钙钛矿型PZT,粒径约为50～100nm.     

巨介电陶瓷CaCu_3Ti_4O_(12)/聚合物复合材料研究进展

介绍了具有巨介电常数的CaCu3Ti4O12陶瓷与聚合物形成复合材料的制备工艺,分析了复合材料介电性能的影响因素,展望了今后巨介电陶瓷CaCu3Ti4O12/聚合物复合材料的发展趋势。     

流延法制备片式CaCu3Ti4O12陶瓷及其性能研究（英文）

片式CaCu3Ti4O12陶瓷由于其巨介电效应,用于制备多层陶瓷片式电容具有重大意义。通过水基流延法并在不同的烧结温度下制备的片式CaCu3Ti4O12陶瓷具有优异的介电性能。其中在1080℃下烧结的样品在保持巨电容率(98605)的同时,降低了介电损耗,其值只有0.028,远低于其他报道的损耗值。同时,测试了CCTO陶瓷薄片的复阻抗图谱,讨论了CCTO陶瓷的特殊的电学性能。实验结果表明,通过流延成型制备的CCTO陶瓷薄片在保持巨电容率的同时具有很低的介电损耗,这为CCTO陶瓷在微电子工业上的应用提供了可能性。     

Ho掺杂对Bi4-xHoxTi3O12陶瓷结构与铁电性能的影响

以Ho为掺杂元素,采用热压烧结方法制备Bi4-xHoxTi3O12陶瓷,重点研究了Ho掺杂量对其物相组成、致密度、微观结构和铁电性能的影响.首先以Bi2O3、TiO2和Ho2O3微粉为原料,利用固相反应在900℃合成出主晶相为Bi4Ti3O12的Bi4-xHoxTi3O12(x=0～0.8)粉体;然后,将合成粉体在850℃、30 MPa条件下热压烧结,当Ho掺杂量x=0～0.4得到了物相单一、整体致密(>99%)的Bi4-xHoxTi3O12陶瓷.随Ho掺杂量的增加,Bi4-xHoxTi3O12陶瓷的剩余极化强度呈现先增大后减小的趋势,主要与氧空位浓度和不同掺杂浓度引起的掺杂位置的不同有关.在Ho掺杂量x=0.4时,其剩余极化强度最大(2Pr=13.92μC/cm2),远大于未掺杂的Bi4Ti3O12陶瓷,说明适量Ho掺杂能有效改善其铁电性能.     

SrTiO_3/CaCu_3Ti_4O_(12)复合陶瓷材料的介电性能

本文采用固相反应法制备了xSrTiO_3/(1-x)CaCu_3Ti_4O_(12)(x=0,0.2,0.4,0.6,0.8,1)复合陶瓷,研究了复合材料的物相、微观结构和宽温度宽频率范围内的介电性能。结果表明:在1348~1600K的温度范围内烧结能够得到致密性良好的xSrTiO_3/(1-x)CaCu_3Ti_4O_(12)(x=0,0.2,0.4,0.6,0.8,1)复合陶瓷。频率为100kHz时,样品的室温介电常数随SrTiO_3含量的增加而减少,从71358(x=0)单调减少至270(x=1),其变化规律遵循Lichtenecker法则。介电损耗随SrTiO_3含量的增加先增大后减少。当x=0.2时,样品与CaCu_3Ti_4O_(12)陶瓷的介电性能相似,存在低温的介电弛豫和巨介电常数平台。随着SrTiO_3含量的增加,复合陶瓷的低温介电弛豫激活能增大,介电响应被抑制,而高温介电响应由于高温电导的影响而增强,使得CaCu_3Ti_4O_(12)特有的巨介电常数平台随着SrTiO_3的增加逐渐消失,xSrTiO_3/(1-x)CaCu_3Ti_4O_(12)复合材料的温度依赖性增强。     

Sintering Behavior and Microwave Dielectric Properties of MgTiO3 Ceramics Doped with B2O3 by Sol-Gel Method

The B2O3-doped MgTiO3 powders and ceramics have been prepared by sol-gel method using Mg(NO3)2·6H2O, Ti(C4H9O)4 and H3BO3 as the starting materials. The sintering behavior and microwave dielectric properties of ceramics prepared from powders with different particle sizes were investigated. The gels were calcined at 650, 700, 750, 800, 850 and 900 C and the derived particle sizes of powders were 20-30 nm, 30-40 nm, 40-60 nm, 60-90 nm, 90-120 nm and 120-150 nm, respectively. The nanoparticles with the size of 30-60 nm benefited the sintering process with high surface energy whereas nanoparticles with the size of 20-30 nm damaged the microwave dielectric properties due to the pores in the ceramics. The addition of B2O3 used as a liquid sintering aid reduced the sintering temperature of MgTiO3 ceramic, which was supposed to enter the MgTiO3 lattice and resulted in the formation of (MgTi)2(BO3)O phase. The B2O3-doped MgTiO3 ceramic sintered at 1100 C and prepared from the nanoparticles of 40-60 nm had compact structure and exhibited good microwave dielectric properties: εr=17.63, Q × f=33,768 GHz and τ f= 48×10 6 C 1.     

Sm2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Sm2O3掺杂的(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(BCZT)无铅压电陶瓷.借助XRD、SEM等手段对该陶瓷的显微结构与电性能进行了研究.结果表明,Sm2O3的掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度点Tc从85℃提高到95℃.当Sm2O3掺杂量为0.02wt%～0.1wt%时,样品具有典型ABO3型钙钛矿结构.Sm2O3掺杂量为0.02wt%时,所得陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因子Qm、介电损耗tanδ和介电常数εr分别为590 pC/N、0.52、43、1.3%和3372.     

CaCu3Ti4O12 nanoparticles using polyvinyl pyrrolidone: synthesis and dielectric properties

Nanocrystalline CaCu3Ti4O12 powders with particle sizes of 39.28 8.12 nm were synthesized by a simple modify sol-gel using PVP (Poly-vinyl-pyrrolidone). The synthesized precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at above 500 degrees C. The precursor was calcined at 800 degrees C in air for 8 h to obtain nanocrystalline powders of CaCu3Ti4O12. The calcined CaCu3Ti4O12 powders were characterized by XRD, FTIR, SEM and TEM. Sintering of the powders was conducted in air at 1100 degrees C for 16 h. The XRD results indicated that all sintered samples have a typical perovskite CaCu3Ti4O12 structure and a small amount of CaTiO3. SEM micrographs showed the average grain sizes of 1.86 +/- 0.69 /m for the sintered CaCu3Ti4O12 ceramic prepared using the CaCu3Ti4O12 powders calcined at 800 degrees C. The sintered samples exhibit a giant dielectric constant, epsilon' of approximately 10(3)-10(4). The large low-frequency dielectric permittivity at low temperature is closely related to sub-grain boundary distribution, including conductivity effect. Furthermore, the ceramic shows three semicircles in the complex impedance plane. However, at low frequency, semicircles of sub-grain boundary and grain boundary are considered to represent collapse different electrical mechanisms. The another is ascribed to the contribution of grain. The dielectric behavior at several frequencies and temperatures of these samples can be attributed to electronic inhomogeneities present in material and can be explained based on a microstructural model.     

Microstructures and Dielectric Properties of Ba1-xSrxTiO3 Ceramics Doped with B2O3-Li2O Glasses for LTCC Technology Applications

Ba1-xSrxTiO3 ceramics, doped with B2O3-Li2O glasses have been fabricated via a traditional ceramic process at a low sintering temperature of 900 ℃ using liquid-phase sintering aids. The microstructures and di- electric properties of B2O3-Li2O glasses doped Ba1-xSrxTiO3 ceramics have been investigated systemat- ically. The temperature dependence dielectric constant and loss reveals that B2O3-Li2O glasses doped Ba1-xSrxTiO3 ceramics have di?usion phase transformation characteristics. For 5 wt% B2O3-Li2O glasses doped Ba0.55Sr0.45TiO3 composites, the tunability is 15.4% under a dc-applied electric field of 30 kV/cm at 10 kHz; the dielectric loss can be controlled about 0.0025; and the Q value is 286. These composite ceramics sintered at low temperature with suitable dielectric constant, low dielectric loss, relatively high tunability and high Q value are promising candidates for multilayer low-temperature co-fired ceramics (LTCC) and potential microwave tunable devices applications.     

Effect of sintering temperature on the properties of modified mechanical alloyed CaCu3Ti4O12

This paper presents the effects of calcination time and sintering temperature on the properties of CaCu(3)Ti(4)O(12). Electroceramic material of CaCu(3)Ti(4)O(12) was prepared using a modified mechanical alloying technique that covers several processes, which are preparation of raw material, mixing and ball milling for 5 hours, calcination, pellet forming and, sintering. The objective of this modified technique is to enable the calcination and sintering processes to be carried out at a shorter time and lower temperature. The x-ray diffraction (XRD) analysis result shows that a single-phase of CaCu(3)Ti(4)O(12) was completely formed by calcination at 750 degrees C for 12 hours. Meanwhile, the grain size of a sample sintered at 1050 degrees C for 24 hours is extremely large, in the range of 20-50 mum obtained from field emission scanning electron microscopy (FESEM) images. The dielectric constant value of 14,635 was obtained at 10 kHz by impedance (LCR) meter in the sintered sample at 1050 degrees C. However, the dielectric constant value of samples sintered at 900 and 950 degrees C is quite low, in the range of 52-119.     

Microstructure and Electromechanical Properties in PMnN-PZT Ceramics Sintered at Different Temperatures

The microstructure and piezoelectric properties of Pb[(Zr0.52Ti0.48)0.95(Mn1/3Nb2/3)0.05]03 (PMnN-PZT) ceramics have been investigated at different sintering temperatures from 1070℃to 1280℃. The experimental results suggest that grain sizes and electromechanical properties of the ceramics show strong sintering temperature dependences. Double polarization to electric field (P-E) loops of the PMnN-PZT ceramics are assumed to be the result of the pinning effect of the defect dipoles. The results obtained through X-ray photoelectron spectrum suggest that sintering temperature affects valence of the Mn ion and quantity of oxygen vacancies. Hence, a proper explanation is proposed to illustrate the fluctuation of mechanical quality factor (Qm) due to the sintering temperature.     

反应烧结法制备(AlN,TiN)-Al2O3复合材料的研究

以Ti,Al,Al₂O₃为初始粉料,通过750~800℃氮气保护下的中温焙烧,然后在1420~1550℃在氮气氛下反应烧结,制备了不同配比的(AlN,TiN)-Al₂O₃复合材料。研究了组成及烧结工艺对复合材料力学性能、显微结构等的影响。用XRD,SEM等方法分析粉体及烧结体的相组成及微观结构。分析结果表明:AlN,TiN的形成,有助于材料的致密化并使其力学性能提高。组成为20wt%(Al,Ti)-Al₂O₃的粉体在1520℃、30MPa、保温、保压30min热压烧结条件下,与N₂气反应可得到硬度(HRA)为 94.1的高硬度的(AlN,TiN)-Al₂O₃复合材料,该材料的抗弯强度为687 MPa,断裂韧性(K_IC)为6.5MPa·m1/2。