热处理温度对纳米晶Ni0.35Zn0.65Fe2O4吸波性能的影响

采用溶胶-凝胶自燃烧法制备了Ni0.35 Zn0.65 Fe2 O4纳米晶,将其分别在550、800和1050℃下热处理2 h,利用XRD、VSM以及微波矢量网络分析仪对产物的晶体结构、电磁性质及其在GHz波段的吸波性能进行了表征.结果表明,自燃烧后即已形成尖晶石相;随着热处理温度的升高,平均粒径从25 nm增至52 nm,均为单畴颗粒.在0.1～1.5 GHz的测试频率范围内,热处理后的纳米晶样品的比饱和磁化强度和矫顽力随温度的升高而增加,从而提高了其自然共振频率,拓宽了其吸收频带.热处理后样品的ε'、ε"、tgδe以及μ'、μ"、tgδm值均随热处理温度的升高而增大,其中以1050℃下热处理样品的电损耗和磁损耗性质最佳,其μ'值大于1.6,且随频率的升高而降低;μ"值大于1.0,且随频率的升高而增大,频率特性良好,在所测频段内是一种理想的电磁波吸收材料.     

MnO2掺杂对Ba0.6Sr0.4TiO3陶瓷介电调谐性能的影响

采用固相反应法制备了掺杂MnO2的Ba0.6Sr0.4TiO3陶瓷,分析了掺杂MnO2的Ba0.6Sr0.4TiO3陶瓷在直流偏置电场下的介电调谐性能.采用XRD和SEM分析了掺杂MnO2的Ba0.6Sr0.4TiO3陶瓷的相结构和微观形貌,采用HP4192A分析了掺杂MnO2的Ba0.6Sr0.4TiO3介电-温度特性,采用同惠电子公司的TH2816精密电桥测量了介电可调性.结果表明:随着MnO2含量的增加,Ba0 6Sr0.4TiO3陶瓷的致密度和晶粒尺寸都呈现先增大再降低的现象.介电可调性随着MnO2的加入而降低.但品质因子随着MnO2含量的增加呈现先增加再降低的现象.当MnO2含量为4mol%时达到最大值55.1.     

MnO2掺杂对Ba0.6Sr0.4TiO3陶瓷介电调谐性能的影响

采用固相反应法制备了掺杂MnO2的Ba0.6Sr0.4TiO3陶瓷,分析了掺杂MnO2的Ba0.6Sr0.4TiO3陶瓷在直流偏置电场下的介电调谐性能.采用XRD和SEM分析了掺杂MnO2的Ba0.6Sr0.4TiO3陶瓷的相结构和微观形貌,采用HP4192A分析了掺杂MnO2的Ba0.6Sr0.4TiO3介电-温度特性,采用同惠电子公司的TH2816精密电桥测量了介电可调性.结果表明随着MnO2含量的增加,Ba0 6Sr0.4TiO3陶瓷的致密度和晶粒尺寸都呈现先增大再降低的现象.介电可调性随着MnO2的加入而降低.但品质因子随着MnO2含量的增加呈现先增加再降低的现象.当MnO2含量为4mol%时达到最大值55.1.     

（Ba，Sr）TiO3薄膜制备技术新进展

（Ba,Sr）TiO3（简称BST）铁电薄膜材料是目前国际上新型功能材料研究的热点之一,本文综述了钛酸锶钡（BST）铁电薄膜目前最常用的4种制备工艺,并简要介绍了BST目前的研究进展、微观结构、性能及应用,深入分析了BST铁电薄膜主要制备技术的优缺点,指出了目前铁电薄膜及其制备技术研究中应注意的问题。     

Ba0.5Sr0.5TiO3铁电薄膜的微弧氧化制备工艺

用分析纯Ba(OH)2·8H2O和Sr(OH)2·8H2O配制电解液(浓度各为0.2 mol/L),采用微弧氧化技术在工业纯钛板(99.5％)表面原位生成BaxSr(1-x)TiO3铁电薄膜.对不同电流密度、电流频率和反应时间条件下获得的薄膜进行表征,研究了各因素对薄膜物相构成、表面形貌和表面粗糙度的影响.结果表明:所得薄膜均主要由四方相Ba0.5Sr0.5TiO3构成;电流密度为20 A/dm2、电流频率为100 Hz、反应时间为10 min时,所得薄膜最平整、致密、表面粗糙度值最小,且微弧氧化孔洞分布最均匀,测得该薄膜在1 kHz条件下的介电常数为411.3.     

溶胶凝胶法制备Zn-Si-B-O掺杂钛酸锶钡(Ba0.60Sr0.40TiO3)玻璃陶瓷的制备及其介电性能研究

采用溶胶凝胶方法制备Zn-Si-B-O掺杂Ba0.6Sr0.4TiO3玻璃陶瓷.研究Zn-Si-B-O玻璃组分从5%～50%(摩尔分数,下同)掺杂Ba0.6Sr0.4TiO3玻璃陶瓷的相结构与介电性能.分析Zn-Si-B-O玻璃组分对Ba0.6 Sr0.4TiO3玻璃陶瓷结构及其介电性能的影响.结果表明:Zn-Si-B-O掺杂Ba0.6Sr0.4TiO3玻璃陶瓷的烧结温度低于传统工艺.Zn-Si-B-O掺杂Ba0.6Sr0.4TiO3玻璃陶瓷的相结构为立方钙钛矿相结构(≤40%),不存在第二相.Zn-Si-B-O掺杂Ba 0.6 Sr 0.4TiO3玻璃陶瓷的介电常数ε随着烧结温度升高而增大,介电损耗tanδ随测试温度的增加而降低.Zn-Si-B-O玻璃相聚集在晶粒边界区域,其作用稀释降低了玻璃陶瓷的介电常数,阻止晶粒生长,并降低了介电损耗tanδ.随着晶粒平均尺寸的减小,Zn-Si-B-O掺杂Ba 0.6Sr 0.4TiO3玻璃陶瓷样品的介电峰变低,平坦,宽化的现象.     

熔盐合成技术制备片状(Sr,Ba)TiO3晶粒

以KCl为助熔剂,采用熔盐合成技术制备片状（Sr,Ba）TiO3晶粒,研究不同前驱体及反应方式对产物相组成和形貌的影响。结果表明：BaO与片状SrTiO3反应可获得以（Sr,Ba）TiO3为主相的产物,产物相在SrTiO3表面无规则析出且非取向长大,经烧结后形成片状多晶团聚体;片状Sr3Ti2O7与BaO和TiO2反应所得产物也以（Sr,Ba）TiO3为主,同时生成少量（Sr,Ba）3Ti2O7相,产物中除片状（Sr,Ba）TiO3晶粒外,还通过Sr^2＋置换由BaO与TiO2反应所得块状BaTiO3晶粒中的Ba^2＋、以及反应物溶解？反应？析出生成许多块状和无规则状小晶粒;对于两步合成工艺,Sr3Ti2O7先与BaO反应可得到片状（Sr,Ba）3Ti2O7,与TiO2二次反应后得到片状（Sr,Ba）TiO3晶粒;由于此方式没有生成块状BaTiO3这一过程,产物中非片状晶粒数量大幅度减少。     

Preparation and properties of Ba3ZnzCo2-zFe24O41／SiO2 microcrystalline glass ceramics

Ba3ZnzCo2-zFe24O41/SiO2(Z varies from 0.0 to 1.2 in step of 0.4) microcrystalline glass ceramics were prepared by citrate sol-gel process at 1200℃ in the system of BaO-Fe2O3-CoO-ZnO-SiO2. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The complex dielectric constant and complex permeability of Ba3ZnzCo2-zFe24O41/SiO2 microcrystalline glass ceramics were measured in the range of 0.1-6.0 GHz by transmission/reflection coaxial line method. The natural resonance phenomenon was observed in μ”spectra for all the Ba3ZnzCo2-zFe24O41/SiO2 microcrystalline glass ceramics, which was closely affected by the substitution of Zn^2 ion.     

Fe_2O_3含量对CaO-Al_2O_3-SiO_2系微晶玻璃显微组织与力学性能的影响(英文)

采用差热分析(DTA)、X射线衍射(XRD)、扫描电镜(SEM)、电子顺磁共振(ESR)和Mssbauer谱等技术研究Fe2O3含量对CaO-Al2O3-SiO2系微晶玻璃显微组织与力学性能的影响。结果表明:Fe2O3的加入不改变CaO-Al2O3-SiO2系微晶玻璃析出的主晶相类型,但使体系的析晶峰温度降低,析晶活化能增加和析出晶体的粒度减小。ESR测试结果表明,Fe2O3的加入会因轴向扭曲造成分相,从而促进析晶;同时,Fe2O3的加入能更好地调整CaO-Al2O3-SiO2系微晶玻璃网络内部结构,使Fe3+进入比四面体对称性更高的八面体配位,有利于抗弯强度的增大。Mssbauer测试结果表明,Fe3+和Fe2+在CaO-Al2O3-SiO2系微晶玻璃存在不同的配位,且微晶玻璃的抗弯强度随Fe3+六配位数的增多而增大;同时,Fe2+和Fe3+相互作用的增强也有利于微晶玻璃抗弯强度的增大。在核化温度为700°C、核化时间为2 h、晶化温度为910°C和晶化时间为3 h的热处理条件下,样品的显微硬度达到HV 896.9,抗弯强度达到217 MPa。     

Microstructure and electrical properties of Lu2O3-doped ZnO-Bi2O3-based varistor ceramics

Lu2O3-doped ZnO-Bi2O3-based varistor ceramics samples were prepared by a conventional mixed oxide route and sintered at temperatures in the range of 900-1 000°C,and the microstructures of the varistor ceramics samples were characterized by X-ray diffractometry(XRD)and scanning electron microscopy(SEM);at the same time,the electrical properties and V-I characteristics of the varistor ceramics samples were investigated by a DC parameter instrument for varistors.The results show that the ZnO-Bi2O3-based varistor ceramics with 0.3%Lu2O3(molar fraction)sintered at 950°C exhibit comparatively ideal comprehensive electrical properties.The XRD analysis of the samples shows the presence of ZnO,Bi-rich,spinel Zn7Sb2O12 and Lu2O3-based phases.     

Structural characteristics and dielectric properties of glass-ceramic nanocomposites of (Pb,Sr)Nb2O6-NaNbO3-SiO2

The structure and dielectric properties of(Pb,Sr)Nb2O6-NaNbO3-SiO2 glass-ceramics with different Pb and Sr contents were investigated.The XRD pattern of glass-ceramics without Sr substitution is different from that with Sr substitution,which indicates the existence of orthorhombic phase in the latter ones.TEM bright field observation shows nanosized microstructures,while for samples with Sr,typical eutectic microstructure with separated crystallized bands is found in the glass matrix.Dielectric properties measurement of the samples indicates an obvious improvement of dielectric constant,dielectric loss,DC field and temperature dependence of dielectric constant when the molar ratio of Sr to Pb is 4:6.     

Crystallization and properties of some CaO-Al2O3-SiO2 system glass-ceramics with Y2O3 addition

The crystallization behavior and mechanical properties of CaO-Al2O3-SiO2 （CAS） system glass-ceramics with addition of Y2O3 were investigated. The optimal sintering temperatures of all heat-treated glasses were altered and the crystallization was accelerated with Y2O3 addition, and only wollastonite as a main crystalline phase was precipitated. The volume fraction of crystalline phase and density were increased with Y2O3 addition. The results suggest that the CAS glass-ceramics would get the lowest sintering temperature and optimal microstructure with the addition of Y2O3 by 3.25 %. The bending strength has a maximum due to the oriented and interlocked wollastonite crystal, which causes crack divert or blunts to limit the further development of the flaw size and increases the surface energy of fracture.     

FeNi/Ba0.6Sr0.4TiO3核壳纳米结构的制备及低频吸波机理研究核壳纳米结构的制备及低频吸波机理研究

采用溶胶凝胶法制备了Ba0.6Sr0.4TiO3粉末,并采用球磨方法将Ba0.6Sr0.4TiO3与FeNi合金微粉进行包覆,成功制备了3种不同Ba0.6Sr0.4TiO3粉末添加量的FeNi/Ba0.6Sr0.4TiO3核壳结构粉体。采用SEM、XRD等技术分析了Ba0.6Sr0.4TiO3加入前后FeNi合金微粉的形态、组成,利用矢量网络分析仪测量了FeNi以及FeNi/Ba0.6Sr0.4TiO3复合材料的电磁参数。结果表明,成功制备了不规则颗粒状Ba0.6Sr0.4TiO3粉末,Ba0.6Sr0.4TiO3粉末大部分包覆于片状FeNi合金微粉表面,且随着Ba0.6Sr0.4TiO3粉末添加量的增加,包覆层厚度逐渐增大,FeNi合金片形态逐渐模糊。Ba0.6Sr0.4TiO3粉末包覆层有效降低了FeNi合金微粉的介电常数虚部,提高了其低频波段的阻抗匹配性能,实现铁电和铁磁双性材料的复合吸波效果,改善了低频吸波性能。利用1/4波长干涉相消理论对反射损耗峰频率与电磁参数关系进行了分析,并结合界面反射模型及材料阻抗匹配对反射损耗峰强度变化进行了分析。     

电泳沉积法制备Ba0．6Sr0．4TiO3厚膜及介电性能研究

采用溶胶凝胶法制备了钛酸锶钡超细粉体，在纯乙醇中配制成悬浮液，利用电泳沉积技术在印刷铂的氧化铝基板上沉积得到了BST厚膜。通过控制悬浮液中粉体的浓度和超声振荡实现了悬浮液的稳定。电泳沉积过程中通过改变电压和沉积时间研究了厚膜质量和厚膜的厚度。利用扫描电子显微镜（SEM）观察了沉积物的微观结构形貌，对沉积质量进行了对比研究。实验结果表明，当外加电场强度为20V／cm，沉积时间为30s时得到的厚膜表面质量较好，厚度适合。实验发现1200℃烧结温度得到的厚膜致密度较好。X射线衍射分析（XRD）图谱表明烧结后得到的BST厚膜具有典型的钙钛矿结构。对厚膜的介电性能测试发现，BST厚膜有一定的介电性能，展示了BST材料的非线性特性。     

掺杂TiO_2对ZnO压敏陶瓷电学性能的影响

以ZnO粉末为主要原料,以TiO2、Bi2O3、MnO2、Co2O3、Sb2O3为组元,在常规电子陶瓷生产工艺下制备低压化ZnO压敏陶瓷。将掺杂TiO2的陶瓷片与未掺杂TiO2的陶瓷片进行对比分析,确定最佳掺杂量。采用能谱仪分析瓷片的微区成分,采用SEM观察瓷片断口形貌,利用压敏电阻直流参数仪测量瓷片的电学性能。研究结果表明,瓷片内部主要存在富Bi晶界、Bi贫化晶界和晶粒直接接触晶界;TiO2对ZnO晶粒有助长作用,不掺杂纳米TiO2陶瓷是11.4μm,掺杂纳米TiO2高达30.5μm;当TiO2掺杂量为1.5%mol时瓷片电学性能较优,即压敏电压为31.2 V/mm、漏电流为0.028 m A及为非线性系数为20.1。     

基于计算热力学的CaO-Al2O3-SiO2熔渣SAW致氧机理分析

基于熔渣的分子离子共存理论,结合高温相图.对CaO-Al2O3-SiO2三元渣系进行了热力学计算,定量分析了不同碱度下熔渣结构单元的变化特征,以及碱度对高温熔渣结构单元活度的影响.通过对CaO-Al2O3-SiO2三元渣系不同碱度下各组元变化规律的分析.定量地解释了随熔渣碱度的增大,熔渣的分子特性相对减弱,而离子特性逐渐明显的原因.对比熔渣不同碱度下,激冷熔滴热化学增氧和电化学增氧的变化趋势,解释了直流埋弧焊正反接时,激冷熔滴含氧量不同的原因,为冶金化学增氧分析提供了一种新的思路.     

Effects of Cr2O3 doping on the electrical properties and the temperature stabilities of PZT binary piezoelectric ceramics

The ceramics with Pb1.04Zr0.52Ti0.48O3 + z wt.% Cr2O3 were prepared using the traditional technique.The effects of Cr2O3 doping on the phase structure,the microstructure,and the electrical properties of ceramics were investigated.Meanwhile,the temperature stabilities of the resonant frequency (fr) were studied.The results showed that the △fr/fr,25℃ decreased with the addition of 0.2 wt.% - 0.8 wt.% Cr2O3 as compared with the undoped samples.The minimum value (-0.182%) of △fr/fr,25℃ was obtained for z = 0.6 wt.% Cr2O3 samples that sintered at 1260℃.The values of εT33/ε0 = 1650,tanδ = 0.006,d33 = 328 pC/N,Kp= 0.63,Qm = 2300 were obtained when Cr2O3 was 0.6 wt.%,which exhibited more excellent piezoelectric properties than other compositions such as those with z = 0.2 wt.%,0.4 wt.%,and 0.8 wt.%,but had a similar value as compared with the undoped samples.When the Cr2O3 additive increased,the Curie temperature moved toward low temperature and the changes of resonant frequency changed from positive to negative with increasing temperature.     

ZnO-B_2O_3对CaCu_3Ti_4O_(12)陶瓷结构和介电性能的影响

采用传统固相反应法,将ZnO-B2O3(ZB)与1 100℃预烧的CaCu3Ti4O12(CCTO)粉末混合烧结成陶瓷。探讨ZB对CCTO陶瓷显微结构和介电性能的影响,并进一步分析CCTO陶瓷的巨介电机理。结果表明:当添加少量ZB(w≤2%,质量分数)时,形成体心立方BCC类钙钛矿结构的CCTO单相;当w>2%时,生成Zn2TiO4杂相;当ZB的添加量为0.5%和10%时,CCTO陶瓷的介电常数明显增大,介电损耗也较高;而当ZB的添加量为1.0%~5.0%时,介电常数的变化很小,同时具有较低的损耗和良好的温度稳定性。其中,w=2%时CCTO基陶瓷具有优异的介电性能(100 kHz),即相对介电常数εr=336,介电损耗tanδ=0.018,介电常数温度系数τε=-1.5×10-5℃-1。ZB掺杂CCTO基陶瓷的阻抗谱表明:CCTO陶瓷由半导体化晶界和相对绝缘的晶粒构成,因此,其具有巨介电常数。