化学溶液沉积法制备Bi4Ti3O12铁电薄膜及其性质的研究

报道了用化学溶液沉积法采用价格低廉的原料在电阻率为 6～ 9Ω·cm的 n型 Si( 1 0 0 )衬底上生长 Bi4 Ti3 O12 铁电薄膜 ,并对薄膜的性质进行了研究。结果表明此制膜工艺简单 ,成本低 ,制备的 Bi4 Ti3 O12 铁电薄膜具有较低的结晶温度 ,且薄膜均匀 ,致密 ,无裂纹。在 650°C下退火 30 min时得到的 Bi4 Ti3 O12 铁电薄膜具有良好的绝缘性和铁电性 ,薄膜的剩余极化 Pr=4.9μC/cm2 ,矫顽电场 Ec=87k V/cm     

La/Nb掺杂对Bi_4Ti_3O_(12)薄膜铁电性能和疲劳特性的影响

采用溶胶–凝胶工艺(sol–gel)在Pt/Ti/SiO2/p-Si衬底上分别制备Bi4–xLaxTi3O12和Bi4Ti3–yNbyO12铁电薄膜,研究La/Nb掺杂对Bi4Ti3O12薄膜铁电性能和疲劳特性的影响。结果表明:La/Nb掺杂均能有效改善Bi4Ti3O12薄膜的铁电性能和疲劳特性。当La摩尔(下同)掺量在0.5～0.75时,La掺杂对Bi4Ti3O12薄膜的性能改善作用最好,而且在明显提高薄膜铁电性能的同时,对薄膜疲劳特性的改善更加显著,薄膜经1010极化反转后,其剩余极化强度(Pr)仅下降5.1%。Nb掺杂对提高薄膜铁电性能的作用更加明显,Nb掺量为0.06时,Bi4Ti3–yNbyO12薄膜的Pr高达18.7μC/cm2,但Nb掺量不宜过多,当Nb掺量超过0.06以后,薄膜的铁电性能和疲劳特性均反而有所下降。     

A位掺杂Bi_4Ti_3O_(12)薄膜的制备及铁电性能研究

采用溶胶-凝胶法制A位掺杂Bi4Ti3O12(BTO)的铁电薄膜Bi3.25La0.75Ti3O12(BLT)、Bi3.15Nd0.85Ti3O12(BNT)及Bi3.15(La0.5Nd0.5)0.85Ti3O12(BLNT);XRD结果表明制备的薄膜具有(117)和(00l)的混合取向;在10V电压下,BLT、BLNT和BNT薄膜的Pr分别为13.14μC/cm2、20.65μC/cm2和21.23μC/cm2;FE-SEM显示BNT薄膜表面光滑致密,颗粒均匀,薄膜厚度约为300nm。     

Li_(1-x)Bi_(4+x)Ti_4O_(15)薄膜制备与表征

在LiNO_3/SiO_2/Si基板上制备了Li_(1-x)Bi_(4+x)Ti_4O_(15)系列薄膜(x=0.3、0.4、0.5、0.6),并系统分析了这些薄膜的微观结构以及铁电、介电及漏电等电学特性。研究结果表明,在氮气气氛中以600℃持温30 min制备的单一相薄膜中Li0.5Bi4.5Ti4O15薄膜的结晶效果最好,且在其表面可成长出独立晶粒分布状态;x为0.5时薄膜的剩余极化强度2Pr=53.5μC/cm2、矫顽场2Ec=144.2 k V/cm,此时薄膜的铁电性能相对最佳;该系列薄膜的介电常数介于37~100,介电损失相对偏高,介于0.7~1.0;所有薄膜的漏电流均随外加电压的增加而逐渐增大,其中Li0.5Bi4.5Ti4O15薄膜漏电流最小,外加电压为10 V时其值约为3.88×10-6A。     

Bi5FeTi3O15薄膜室温多铁性及其磁性机理

用溶胶凝胶工艺在Pt/Ti/SiO2/Si基片上沉积了Bi5FeTi3O15(BFTO)薄膜,研究了前驱液浓度和退火升温速率对BFTO薄膜结晶的影响,前驱液浓度低于0.05mol/L时不利于4层层状钙钛矿结构的形成。沉积BFTO薄膜的最佳制备工艺为:前驱液浓度为0.05mol/L和氧气氛中退火速率为4℃/s。室温下,用最佳工艺制得的BFTO薄膜显示出良好的铁电性,在300 kV/cm的外加电场下,样品的剩余极化强度2Pr达到43.4μC/cm2;同时,BFTO薄膜也显示出弱铁磁性。为了研究其磁性来源,分别在氧气氛和氮气氛下对BFTO薄膜样品进行退火,分析其磁性的差异。认为BFTO薄膜室温下的弱铁磁性主要来源于F中心交换作用。     

钛酸铋陶瓷靶材的热压烧结

纯相、高致密度、结晶良好的陶瓷靶材是物理气相沉积薄膜的前提.采用热压烧结方法制备钛酸铋(Bi4Ti3O12)陶瓷靶材,重点研究了制备工艺对靶材的物相、微观结构和致密度的影响.以Bi2O3和TiO2微粉为原料,采用固相反应法,在800℃合成出纯相的Bi4Ti3O12粉体;加入过量3wt%的Bi2O3,可以有效防止烧结过程中因Bi挥发所产生的杂相,得到纯相的Bi4Ti3O12陶瓷;采用热压烧结方法,进一步实现了Bi4Ti3O12粉体的致密烧结,确定了适宜的制备条件为850℃,30MPa,2b,在该条件下制备的Bi4Ti3O12陶瓷致密度达到99%,晶粒呈片层状,大小约2-4μm,可满足靶材制备薄膜的需求.     

分子筛负载钛酸铋光催化剂的制备及性能研究

采用溶胶-凝胶法制备粉末Bi4Ti3O12光催化剂,研究煅烧温度、煅烧时间对其活性的影响,确定了Bi4Ti3O12的制备条件。将HZSM-5作为载体,采用机械混合和溶胶-凝胶法制备负载型χBi4Ti3O12/HZSM-5催化剂。结果表明,700℃下煅烧5 h的Bi4Ti3O12活性最高;与HZSM-5机械混合使Bi4Ti3O12活性略有降低;HZSM-5抑制溶胶-凝胶法合成Bi4Ti3O12,导致其活性显著下降。     

热处理工艺对钙锶铋钛铁电薄膜性能的影响

用溶胶-凝胶法和快速退火技术在带白金电极和钛过渡层的硅片(Pt/Ti/SiO2/Si)上制备了钙锶铋钛(Ca0.4Sr0.6Bi4Ti4O15,CsBT-0.4)铁电薄膜.结果表明:退火温度及保温时间对CSBT-0.4铁电薄膜的微观结构、晶粒取向以及铁电性能的影响较大.x射线衍射谱表明:退火温度为750℃、保温时间为5min,得到的CsBT-0.4铁电薄膜样品的晶粒大小较均匀且致密性好,而且晶粒以a轴取向的球状晶粒为主,剩余极化强度(2Pr)和矫顽场(2Ec)分别为16.2 μC/cm2和130kV/cm.     

双重熔盐法制备片状BaTiO_3粉体

用双重熔盐法制备片状Bi4Ti3O12粉体,以Bi4Ti3O12为中间产物通过离子交换制备了BaTi03片状粉体,并对其工艺过程进行了优化.利用X射线衍射分析合成粉体的相结构,用扫描电子显微镜观察其显微形貌.初步探讨了BaTiO3片状粉体的生长机理.结果表明:反应温度和化学组成对中间产物Bi4Ti3O12的微观形貌具有显著影响,在1 000℃以下时,随着反应温度升高,片状尺寸增大;当相对增加Bi2O3的量时,Bi4Ti3O12片状的尺寸增大.通过离子交换制备BaTiO3时,除了模板Bi4Ti3O12的形貌对BaTiO3的晶粒生长具有影响外,反应温度和化学组成同样对BaTiO3的晶粒生长具有显著影响.合成片状Bi4Ti3O12粉体的最佳的条件为:BaTiO3与Bi4Ti3O12的摩尔比为10:1,1 000℃合成2h.     

射频磁控溅射制备PZT铁电薄膜的工艺研究

在SiO2/Si基片上采用直流对靶溅射技术制备出Pt/Ti底电极;应用射频磁控溅射方法,利用快速热处理(RTA)工艺,制备出了具有良好铁电性能的Pb(Zr0.52Ti0.48)O3铁电薄膜.将样品进行10min快速热退火处理,退火温度700℃.测试分析表明:薄膜厚度比较均匀、表面基本平整、没有裂纹和孔洞、致密性好、薄膜样品的矫顽场强(Ec)为28.6kV/cm,剩余极化强度(Pr)为18.7μC/cm2,自发极化强度(Ps)为37.5μC/cm2,是制备铁电薄膜存储器的优选材料.     

Graphite trifluoromethylsulfate C12+SO3CF3−

Graphite trifluoromethylsulfate C₁₂SO₃CF₃, a new binary graphite salt is formed by the irreversible solvolysis of C₈SO₃F in a large excess of trifluoromethylsulfuric acid. The salt is identified as a stage one intercalation compound with a C₀ value of 8.12 Å and characterised by microanalysis, epr and ¹⁹F NMR spectroscopy. Both Raman spectra, in the back scattering configuration, and IR spectra, in transmission as well as reflection geometries, are used to support an ionic formulation as C₁₂⁺SO₃CF₃^?.     

Composite cathodes of La0.9Ca0.1Ni0.5Co0.5O3-Ce0.8Sm0.2O1.9 for solid oxide fuel cells

The mixed ionic and electronic conductors of La_0.9Ca_0.1Ni_0.5Co_0.5O₃-Ce_0.8Sm_0.2O_1.9 (LCNC-SDC) are investigated systematically for potential application as a cathode for solid oxide fuel cells based on a Ce_0.8Sm_0.2O_1.9 (SDC) electrolyte. The electrochemical impedance spectroscopy (EIS) measurements are performed in air over the temperature range of 600-850 °C to determine the cathode polarization resistance. The exchange current densities for oxygen reduction reaction (ORR), determined from the low-field cyclic voltammetry, high-field cyclic voltammetry, and EIS data are systematically investigated. The activation energies (E_a) for ORR determined from the slope of Arrhenius plots are in the range of 102.33-150.73 kJ mol⁻¹ for LCNC-SDC composite cathodes. The experimental results found that LCNC-SDC (70:30) composite cathode has a maximum exchange current density and a minimum polarization resistance of 0.30 Ω cm² for 850 °C among LCNC-SDC composite cathodes.     

Dielectric relaxation and resistive switching of Bi0.96Sr0.04Fe0.98Co0.02O3/CoFe2O4 thin films with different thicknesses of the Bi0.96Sr0.04Fe0.98Co0.02O3 layer

Bi_0.96Sr_0.04Fe_0.98Co_0.02O₃/CoFe₂O₄(BSFCO/CFO) bilayered thin films with different thicknesses of the BSFCO layer are synthesized on FTO/glass substrates by chemical solution deposition method (CSD). The influence of BSFCO thickness on the microstructure, dielectric relaxation, ferroelectric properties and resistive switching (RS) of the thin films are researched. Strain exists in the prepared thin films and gives rise to structural distortion, which has an effect on charged defects and ferroelectric polarization. Dielectric relaxation that is closely related to the interfacial polarization at the BSFCO/CFO interface is observed, and the dielectric loss peaks along with decreasing intensity shift to high frequency with decreasing strain. The Maxwell-Wagner two-layer model is adopted to investigate the mechanism of dielectric relaxation, and the relaxation time τ is calculated and it shown to be directly proportional to the strain. It is found that the dielectric properties, including low dielectric loss, can be improved by controlling the BSFCO layer thickness. The ferroelectric properties improve with the decreasing strain, the 12-BSFCO/CFO thin film possesses a large P_r ~ 102.9?μC/cm² at 660?kV/cm. The observed resistive switching (RS) behavior is attributed to the interfacial conduction mechanism, it is found that strain-dependent the ferroelectric polarization switching modulates the width of depletion layer and the height of potential barrier at the interface, resulting in the different resistance states.     

Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3–BaTiO3–SrTiO3陶瓷的准同型相界与电性能

采用固相法制备了 Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3–BaTiO3–SrTiO3（NBT–KBT–BT–ST）陶瓷,该体系是按（1–2x）（0.8NBT–0.2KBT）–x（0.94NBT–0.06BT）–x（0.74NBT–0.26ST） （x = 0.10、0.20、0.25、0.30、0.35、0.40、0.45）组合而成的,研究了该系陶瓷的结构与电性能。结果表明：所有样品都处于三方–四方准同型相界区域。该系陶瓷在准同型相界附近表现出了优异的压电性能,压电常数 d33、机电耦合系数 kp和剩余极化强度 Pr随 x 的增加先升高后降低,其中 x=0.35 陶瓷的电性能最佳：d33= 210 pC/N,kp= 0.319,Pr= 39.3 μC/cm2,Ec= 20.2 kV/cm,是一种良好的无铅压电陶瓷候选材料。依据准同型相界组成的线性组合规律来寻找具有优异压电性能的 NBT–KBT–BT–ST 陶瓷准同型相界组成是可行的。     

Ni~(2+)-Fe~(3+)-C_7H_7SO_3~--LDHs催化剂的制备

以尿素为沉淀剂,柠檬酸钠为络合剂,采用均相沉淀法制备Ni~(2+)-Fe~(3+)-CO_3~(2-)-LDHs。以制备的Ni~(2+)-Fe~(3+)-CO_3~(2-)-LDHs为前驱体,分别与Na Cl和对甲苯磺酸钠进行离子交换反应得到Ni~(2+)-Fe~(3+)-C_7H_7SO_3~--LDHs新型催化剂,成功实现对甲苯磺酸根负载Ni~(2+)-Fe~(3+)-LDHs。研究表明,Ni~(2+)-Fe~(3+)-C_7H_7SO_3~--LDHs为介孔材料,比表面积为165.6 m~2·g~(-1),平均孔径为14.7 nm,较大比表面积和空隙结构增强了其吸附性能和催化活性。     

ZrO2/SiO2- and La2O3/Al2O3-supported platinum catalysts for CH4/CO2 reforming

Surface-phase ZrO₂ on SiO₂ (SZrOs) and surface-phase La₂O₃ on Al₂O₃ (SLaOs) were prepared with various loadings of ZrO₂ and La₂O₃, characterized and used as supports for preparing Pt/SZrOs and Pt/SLaOs catalysts. CH₄/CO₂ reforming over the Pt/SZrOs and Pt/SLaOs catalysts was examined and compared with Pt/Al₂O₃ and Pt/SiO₂ catalysts. CO₂ or CH₄ pulse reaction/adsorption analysis was employed to elucidate the effects of these surface-phase oxides.

The zirconia can be homogeneously dispersed on SiO₂ to form a stable surface-phase oxide. The lanthana cannot be spread well on Al₂O₃, but it forms a stable amorphous oxide with Al₂O₃. The Pt/SZrOs and Pt/SLaOs catalysts showed higher steady activity than did Pt/SiO₂ and Pt/Al₂O₃ by a factor of three to four. The Pt/SZrOs and Pt/SLaOs catalysts were also much more stable than the Pt/SiO₂ and Pt/Al₂O₃ catalysts for long stream time and for reforming temperatures above 700 °C. These findings were attributed to the activation of CO₂ adsorbed on the basic sites of SZrOs and SLaOs.     

Photocatalytic activity of Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions

Cu₂O/TiO₂, Bi₂O₃/TiO₂ and ZnMn₂O₄/TiO₂ heterojunctions were studied for potential applications in water decontamination technology and their capacity to induce an oxidation process under VIS light. UV–vis spectroscopy analysis showed that the junctions-based Cu₂O, Bi₂O₃ and ZnMn₂O₄ are able to absorb a large part of visible light (respectively, up to 650, 460 and 1000 nm). This fact was confirmed in the case of Cu₂O/TiO₂ and Bi₂O₃/TiO₂ by photocatalytic experiments performed under visible light. A part of the charge recombination that can take place when both semiconductors are excited was observed when a photocatalytic experiment was performed under UV–vis illumination. Orange II, 4-hydroxybenzoic and benzamide were used as pollutants in the experiment. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena that were observed in each case are discussed.     

A bi-layered composite cathode of La0.8Sr0.2MnO3-YSZ and La0.8Sr0.2MnO3-La0.4Ce0.6O1.8 for IT-SOFCs

A bi-layered composite cathode of La_0.8Sr_0.2MnO₃ (LSM)-YSZ and LSM-La_0.4Ce_0.6O_1.8 (LDC) was fabricated for anode-supported solid oxide fuel cells with a thin YSZ electrolyte film. The cell with the bi-layered composite cathode displayed better performance than the cell with the corresponding single-layered composite cathode of LSM-LDC or LSM-YSZ. At 650 °C, the cell with the bi-layered composite cathode gave a higher maximum power density than the cells with the single-layered LSM-LDC and LSM-YSZ composite cathodes, by 52% and 175%, respectively. The impedance spectra results show that the thin LSM-YSZ interlayer not only improves the cathode/electrolyte interface but also reduces the polarization resistance of the cathode. The activation energy for oxygen reduction on the bi-layered composite cathode is much smaller than that on LSM-YSZ composite cathode, and it is suggested that the special redox property of Ce⁴⁺/Ce³⁺ in LDC facilitates the oxygen reduction process on the bi-layered composite cathode. The cell with the bi-layered composite cathode operated quite stably during a 100 h run.     

Preparation and characterization of Cr2O3-TiO2-Al2O3-V2O5 green pigment

Green pigments with high near infrared reflectance based on a Cr₂O₃-TiO₂-Al₂O₃-V₂O₅ composition have been synthesized. Cr₂O₃ was used as the host component and mixtures of TiO₂, Al₂O₃ and V₂O₅ were used as the guest components. TiO₂, Al₂O₃, and V₂O₅ were mixed into 39 different compositions. The spectral reflectance and the distribution of pigment powder were determined using a spectrophotometer and a scanning electron microscope, respectively. It was found that a pigment powder sample S9 with a Cr₂O₃-TiO₂-Al₂O₃-V₂O₅ composition of 80, 4, 14 and 2 wt%, respectively, gives a maximum near infrared solar reflectance of 82.8% compared with 49.0% for pure Cr₂O₃. The dispersion of pigment powders in a ceramic glaze was also studied. The results show that the pigment powder sample S9 is suitable for use as a coating material for ceramic-based roofs.