Y3+掺杂BST/ZrO2复合薄膜的制备及介电性能研究

运用溶胶-凝胶法在Si/SiO2/Ti/Pt基底上制备了掺杂不同量的Y3+的单层Ba0.65Sr0.35TiO3 (BST)薄膜和并联结构的BST/ZrO2复合薄膜.研究发现:当BST溶胶中掺入了适量的Y3+后,制备的单层BST的表面形貌得到改善,介电性能提高;掺杂的Y3+为1mol;时单层BST薄膜介电性能最佳,介电常数为400.53;介电损耗为0.0125.BST/ZrO2复合薄膜的电容值相对于单层BST薄膜得到明显提高,当烧结温度为750℃时,BST/ZrO2复合薄膜综合介电性能最佳,介电常数790.12;介电损耗达到0.051.     

Ba0.6Sr0.4TiO3/PVDF复合材料电性能研究

采用直接沉淀法制备了顺电体钛酸锶钡(Ba0.6Sr0.4TiO3)纳米粉体,用钛酸酯偶联剂将Ba0.6 Sr0.4TiO3纳米粉体改性后与聚偏氟乙烯(PVDF)进行物理共混制备Ba0.6Sr0.4TiO3/PVDF复合材料薄膜.XRD图谱分析表明,Ba0.6Sr04TiO3粉体晶相皆为立方相,经TEM分析发现颗粒形貌呈球形,粒径约为50 nm,分散性好.在低比例纳米Ba0.6Sr0.4TiO3粉体掺入下,复合材料的介电常数和击穿场强与纯PVDF相比有显著提高,在粉体的含量约为7vol;时,材料的介电常数为12,击穿场强达到289 kV/mm,储能密度最大.     

钛酸锶钡纳米管阵列薄膜的水热合成及其性能研究

以阳极氧化法制备的二氧化钛纳米管阵列为模板,结合水热法制备了钛酸锶钡纳米管阵列薄膜.讨论了Ba1-xSrxTiO3纳米管阵列薄膜的结构、形貌和电学性能.用X射线衍射仪表征其晶体结构;扫描电子显微镜观察其表面及断口形貌;以及用宽频介电阻抗谱仪测试其介电性能.结果表明:在较为温和的条件下用水热法制备了立方相及四方相的Ba1-xSrxTiO3纳米管阵列薄膜;纳米管孔径在65～ 80 nm之间,薄膜厚度可达10 μm以上;经热处理之后的薄膜样品在1 kHz介电常数可达338,介电损耗为0.46.     

0-3型PLZT/IPN压电复合材料制备和电性能研究

采用溶胶-凝胶法确定镧改性锆钛酸铅(PLZT)凝胶粉体的制备工艺流程,采用TG-DTA热分析确定了凝胶粉体的热处理工艺,获得粉体颗粒尺寸分布均匀,最小颗粒尺度可达到纳米级的PLZT陶瓷粉体。研究了La掺杂浓度和预烧温度对粉体晶型转变和陶瓷性能的影响。确定较佳的掺杂浓度为2 wt%,较佳的预烧温度为700~870℃。在此基础上,采用溶液混合法制备了0-3型PLZT/互穿聚合物(IPN)压电复合材料,考察了复合材料的形貌以及频率对PLZT介电性能的影响。结果表明,粉体在复合体系中保持良好的分散状态,分布较为均匀,孔隙较少;La的掺杂浓度增加,陶瓷相的介电常数和介电损耗增加;而复合后体系的介电常数和介电损耗均有所降低。     

A位复合铁电陶瓷BNT-BKT-BiCoO3的介电特性

采用传统陶瓷制备工艺,制备了一种A位复合铁电陶瓷(1-x-y)BNT-xBKT-yBiCoO3,并研究了该体系陶瓷的介电性能与成分的关系以及介电性能随频率的变化规律.结果表明:所研究的组成极化后的介电常数低于极化前.极化前的介电常数和介电损耗随BiCoO3含量的增加而下降,极化前和极化后的介电常数和介电损耗都随BKT含量的增加而增加.介电常数随频率增加而降低,但降低趋势随频率增加而减慢.随BiCoO3含量的增加,在低频陶瓷介电损耗随频率的增加先降低后增加.     

AlN/Mo/TiB2微波衰减材料的制备及介电性能研究

采用放电等离子烧结制备了AlN/Mo/TiB2微波衰减材料.研究了TiB2的含量对复合材料的相组成、致密度、电阻率及介电性能的影响.利用XRD、SEM、网络分析仪对样品的相组成、微观结构、介电性能进行测试分析.结果表明:随着TiB2的含量的增加,复合陶瓷的致密度先增大后减小,当加入15wt; TiB2时,致密度达到最大,为98.71;.加入TiB2有利于复合陶瓷介电常数和介电损耗的增加.从电导率测试结果可知,复合陶瓷的渗流阈值在TiB2含量为15wt;.     

高介电常数CaCu3Ti4O12陶瓷粉体的合成与烧结

采用固相合成及常压烧结的方法制备了CaCu3Ti4O12(CCTO)高介电常数陶瓷材料,采用XRD、SEM、LCR等测试手段对合成与烧结过程以及介电性能进行了研究.结果表明,在温度高于1000℃时,CaCO3、CuO和TiO2可完全反应生成CCTO;温度高于1150℃时,CCTO分解.CCTO合成粉体的适宜烧结温度为1100℃,烧结试样结晶完整,结构致密,1kHz频率下相对介电常数达1.5×104,介电损耗0.27.     

Sn、Tb复合掺杂钛酸钡陶瓷的制备及介电性能研究

采用传统固相法制备Sn、Tb复合掺杂BaTb0.01SnxTi0.99-xO3(x=0、0.05、0.10、0.15)陶瓷,借助X射线衍射、扫描电镜和阻抗分析仪研究Sn、Tb复合掺杂以及Sn掺杂量对钛酸钡陶瓷结构及介电性能的影响.结果表明,掺入SnO2后仍可保持单一钙钛矿结构,并且样品晶粒细化.当Sn掺杂量为10mol;,烧结温度为1350℃时,Sn、Tb复合掺杂BaTb0.01Sn0.1Ti0.89O3陶瓷居里峰移向低温,室温介电常数显著提高,可以达到9069,介电损耗仅为0.011.     

Al2O3改性Ba(Fe0.5Nb0.5)O3复合陶瓷制备与性能研究

采用草酸盐共沉淀法成功合成了Ba(Fe0.5Nb0.5)O3 (BFN)纳米粉体,并采用sol-gel法获得Al2O3改性的BFN复合粉体,于1150℃两步烧结3h获得复合陶瓷,研究了Al2O3添加对BFN陶瓷微观形貌和介电性能的影响.结果表明:BFN · xAl2O3(x=4wt;,6wt;,8wt;)复合粉体颗粒分布均匀,粒径约为50 nm.Al2O3的加入可明显降低陶瓷的烧结温度.Al2 O3添加量为4wt;的复合陶瓷有高的介电常数,较小的介电损耗和良好的温度稳定性.BFN·xAl2O3复合陶瓷中存在的介电弛豫行为符合Arrhenius定律,是一个热激活过程,随着x的增加,复合陶瓷的激活能逐渐增大,这与无定形Al2O3增加了陶瓷的弛豫势垒,使界面极化减弱相关.     

氧化钽薄膜的结构、成份和介电性能研究

采用直流磁控反应溅射技术制备氧化钽薄膜,重点研究了溅射气体中Ar:O2比例和退火温度对样品的结构.成份和介电性能的影响.XRD、XPS和介电谱分析表明:Ar:O2比例对薄膜的结晶性能和薄膜中O/Ta原子比有较大影响,但对薄膜的介电性能没有明显的影响.900℃退火后,XRD谱中出现明显的β-Ta2O5(001)和(200)衍射峰;介电损耗谱表明介质的损耗是由微弱的电导产生的,漏电电流在损耗中占主导地位.     

Characterization of optical properties of amorphous BaTiO3 nanothin films

Amorphous barium titanate nanothin films were prepared by sol–gel dip-coating method. According to transmission spectrum, the refractive index and optical band gap of nanothin films have been determined. High transmission spectrum without any fluctuation in visible wavelength region was recorded. Experimental results indicated that the surface morphology of prepared nanothin films were improved and as a result of that, a better optical properties, less optical losses and higher band gap width were obtained in contrast with other reported data. It was found that optical propagation loss of BaTiO₃ nanothin film was much lower than normal polycrystalline BaTiO₃ thin film. It seems to us that, amorphous barium titanate nanothin films would be suitable for several applications.     

Bi1.65Zn1.0Nb1.5O7.225陶瓷和薄膜的结构和介电性能对比

以立方焦绿石Bi1.5Zn1.0Nb1.5O7(BZN)为配方基础,通过掺入过量10％的Bi2O3,形成Bi1.65Zn1.0Nb1.5O7.225非化学计量比分子式.采用固相反应法合成具有焦绿石立方结构的Bi1.65Zn1.0Nb1.5O7.225陶瓷,并采用脉冲激光沉积法在Pt/SiO2/Si(100)基片上制备其薄膜.对比研究了非化学计量比Bi1.5Zn1.0Nb1.5O7.225陶瓷和薄膜的结晶性能,微观形貌以及介电性能的差异.结果表明烧结的Bi1.65Zn1.0Nb1.5O7.225陶瓷和沉积的BZN薄膜都保持立方焦绿石单相结构,但是薄膜展现出较强的(222)晶面择优取向.陶瓷和薄膜的晶格常数,微观形貌都体现出差异.对比二者的介电特性后发现,Bi1.65Zn1.0Nb1.5O7.225薄膜的介电常数明显高于陶瓷的介电常数,这归因于薄膜和块体材料之间的差异,例如厚度,致密度,择优取向等.     

二氧化钛表面改性及其涂布膜光催化性能的研究

采用硅烷偶联剂和钛酸酯偶联剂对二氧化钛进行表面改性,利用粒径和Zeta电位等表征得出最佳改性条件.结果表明,钛酸酯偶联剂对粉体表面改性效果更优.将偶联后的粉体分散在聚乙烯醇中,用涂布的方式将其涂覆在双向拉伸聚丙烯薄膜上,制备了有良好光催化性能的二氧化钛涂布膜.采用微型光泽仪、摩擦系数测定仪、雾度仪等分析了薄膜各项物理性能,当粉体加入量为1;时,涂布膜具有最优的机械性能.通过抗菌和光降解实验分析了涂布膜的光催化性能,当粉体加入量为2;时,薄膜抗菌效果达到最佳的99.2;,并对有机染料降解效果提高近70倍.     

双氧水对溶胶-凝胶法制备硅酸锆薄膜的影响

以氧氯化锆和正硅酸乙酯为锆源和硅源,采用溶胶-凝胶法制备硅酸锆薄膜.借助SEM、DTA-TG、FT-IR、XRD等分析测试手段研究了添加双氧水(H2O2)对制备硅酸锆薄膜的影响,并研究了薄膜的抗腐蚀性能.结果表明:适量的双氧水可以有效地促进氧氯化锆的水解,进而克服薄膜高温失重造成孔洞和致密性差的问题;当H2O2/Zr的摩尔比小于2时,制备的薄膜不致密、不均匀;当H2O2/Zr的摩尔比大于2时,制备的样品有杂质相;最优的H2O2/Zr摩尔比为2,可制得均匀、致密的硅酸锆薄膜;所制备的薄膜具有较好的抗NaOH溶液腐蚀性能,单晶硅基片腐蚀前后质量损失为16.92;,而镀有硅酸锆薄膜的单晶硅基片腐蚀前后质量损失仅为0.56;.     

MOCVD of titanium dioxide on the basis of new precursors

Thin films with a considerably higher dielectric constant than silicon dioxide, for example titanium dioxide or titanium containing barium strontium titanate, can be used for dielectrics in ultralarge scale integration devices. TiO₂ shows, besides its high dielectric constant, a sufficiently low leakage current and high breakdown field strength. MOCVD is the most promising method for depositing those dielectrics because of its obvious advantages like homogeneity of films, good step coverage and ultrathin film deposition. In this work, three new precursor chemicals have been developed and tested in a low pressure horizontal cold wall-type furnace. For the synthesis of the novel precursors, commercial titaniumisopropylate is brought to an reaction with an alcoholic compound at 150 °C and distilled under vacuum. The motivation for the development of new Ti precursors lies in an improvement of the handling and deposition characteristics as for example the hydrolytic stability. For the three precursors the deposition parameters temperature, pressure, gas flow and activation energy is presented. The electrical properties dielectric constant and leakage current were compared to commercially available titaniumisopropylate.     

Structure and properties of self-assembled fluorocarbon–silica nanocomposites

The formation of fluorocarbon–silica nanocomposites by the self-assembly of a fluorinated surfactant and aminoalkoxysilane coupling agents was studied by X-ray diffraction, electron microscopy, NMR spectroscopy and thermal analysis. The prepared materials posses a lamellar nanostructure consisting of non-crystalline fluorinated and condensed silica layers, the latter being very thin. The prepared materials show interesting properties for applications, such as hydrophobicity, thermal stability, high content of aminopropyl groups and low dielectric constant (≈2.8), which is almost independent on frequency. Moreover, the dielectric response can be interpreted in the framework of the Maxwell–Wagner model.     

Growth and optical property characterization of textured barium titanate thin films for photonic applications

We have investigated the growth of barium titanate thin films on bulk crystalline and amorphous substrates utilizing biaxially oriented template layers. Ion beam-assisted deposition was used to grow thin, biaxially textured, magnesium oxide template layers on amorphous and silicon substrates. Growth of highly oriented barium titanate films on these template layers was achieved by molecular beam epitaxy using a layer-by-layer growth process. Barium titanate thin films were grown in molecular oxygen and in the presence of oxygen radicals produced by a 300 W radio frequency plasma. We used X-ray and in situ reflection high-energy electron diffraction (RHEED) to analyze the structural properties and show the predominantly c-oriented grains in the films. Variable angle spectroscopic ellipsometry was used to analyze and compare the optical properties of the thin films grown with and without oxygen plasma. We have shown that optical quality barium titanate thin films, which show bulk crystal-like properties, can be grown on any substrate through the use of biaxially oriented magnesium oxide template layers.     

Dielectric properties and AC conductivity studies of novel NR/PVA full-interpenetrating polymer networks

Fully interpenetrating polymer networks (IPN) based on natural rubber (NR) and polyvinyl alcohol (PVA) were prepared by using Glutaraldehyde as the common crosslinking agent. Crosslinking reactions were confirmed by Fourier Transform Infra-red Spectroscopy. The electrical properties of full-IPN have been studied in the frequency range of 10²–10⁶ Hz. The dielectric constant, dielectric loss and ac conductivity were analyzed as a function of frequency, temperature and blend composition. It was found that the dielectric constant and dielectric loss increased with the addition of PVA into NR. Interpenetrated system showed a significant reduction in dielectric constant and dielectric loss and almost frequency independent. The dielectric constant and dielectric loss were increased with increase in temperature. The change in these parameters with temperature in the IPN system was found too low as compared to the pure blends. The ac conductivity study revealed that the IPN materials exhibited a considerable reduction in conductivity.     

沉积氧压对Bi1.5ZnNb1.5O7薄膜的结构和介电特性的影响

采用固相反应法合成具有焦绿石立方结构的Bi1.5ZnNb1.5O7(BZN)陶瓷靶材,采用脉冲激光沉积法在Pt/SiO2/Si(100)基片上制备立方BZN薄膜。研究了沉积氧压的变化对薄膜的结晶性能,微观形貌以及介电性能的影响。结果表明:沉积的BZN薄膜都呈现出立方焦绿石单相结构,但是薄膜的取向随氧压变化而变化。当沉积氧压为10 Pa时,薄膜的(222)晶面拥有最强的择优取向。随着氧压的升高,BZN薄膜的介电常数明显降低。在10 Pa氧压下沉积的BZN薄膜展示出介电可调特性为5%(500 kV/cm)。     

还原氧化石墨烯/TiO2纳米线复合膜的制备及对Cu2+吸附性的影响

以石墨烯和自制TiO₂粉末为原料,通过两步水热法联合真空抽滤法制备还原氧化石墨烯/TiO₂纳米线(rGO/TiO₂ NWs)复合膜。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、拉曼光谱对rGO/TiO₂ NWs复合膜的形貌、结构进行表征。研究结果表明,还原氧化石墨烯和TiO₂ NWs成功地复合在一起,复合材料中TiO₂ NWs分散性较好。Cu²⁺吸附实验结果表明,复合材料中TiO₂ NWs所占比例、pH值是影响Cu²⁺吸附效果的重要因素,研究复合材料对Cu²⁺的吸附效果应该在pH值为6.0的近中性环境。其中TiO₂ NWs含量为50%时,复合膜对Cu²⁺的吸附量最高,达到rGO薄膜的4倍。复合薄膜有较好的吸附稳定性,重复使用5次后,吸附率是原吸附量的91%。