本文采用快速液相烧结法制备了Gd2O3掺杂BiFeO3陶瓷, 并对陶瓷样品进行了物相、形貌、漏电流特性和磁性能研究。XRD分析结果表明, Gd2O3的加入促进了富铋相(Bi25FeO40)的形成且使晶胞体积减小, 同时陶瓷的物相由三方相向正交相转变; SEM分析结果表明, Gd2O3掺杂能起到细化陶瓷晶粒的作用; 电学性能分析表明, 陶瓷样品漏电流较大, 但Gd2O3的掺杂可显著降低陶瓷的漏电流; 漏电流特性分析结果表明, 陶瓷在低电场下的漏电流特性是欧姆传导机制, 在高电场下纯BiFeO3陶瓷的漏电流特性为肖特基发射机制, 但随着Gd2O3掺杂量的增加而逐渐变为空间电荷限制电流传导(SCLC)机制; 磁性研究结果表明, 掺杂引入的磁性Gd2O3颗粒均匀分布在陶瓷的晶界处从而显著提高陶瓷磁性能。

采用溶胶-凝胶法在Pt/Ti/SiO2/Si衬底上成功制备了BiFe1-xZnxO3(BFZO)(x=0、2%、4%、6%)(摩尔分数)薄膜, 并系统研究了Zn掺杂对BiFeO3(BFO)薄膜结构、表面形貌、漏电流密度、铁电及铁磁性能的影响。XRD图谱显示, 所有样品均为钙钛矿结构, 无其他杂质相引入。扫描电子显微镜(SEM)测试表明, 当Zn掺杂量(x)为4%时, BFZO薄膜表现出均匀的细晶粒和更高的密度, 有助于改善漏电流密度。漏电流密度曲线表明, 在300 kV/cm的电场下, BiFe0.96Zn0.04O3薄膜的漏电流密度(J)最低为1.56×10-6 A/cm2, 比纯BFO薄膜的低3个数量级。同时, BiFe0.96Zn0.04O3薄膜在室温下表现出较大的剩余极化(2Pr=20.91 μC/cm2), 是BFO(2Pr=4.96 μC/cm2)的4倍多。此外, Zn掺杂也增强了BFO薄膜的铁磁性能, 随着Zn掺杂浓度的提高, BFZO薄膜的饱和磁化强度显著增强, 使BiFeO3薄膜在信息存储方面存在潜在的应用价值。

In this work, Li₂CO₃ was added into 0.7BiFeO3?0.3BaZr0.02Ti0.98O3?0.01molMnO₂ (70BFBTMn) piezoelectric ceramics to reduce their sintering temperatures. 70BFBTMn ceramics were sintered by a conventional solid reaction method, and their structural, dielectric, piezoelectric and ferroelectric properties were studied. These results indicate that 0.5% (mole) Li₂CO₃ is the optimized content and it can reduce the sintering temperature by 100°C, making the possibility of the piezoelectric ceramics cofiring with Ag electrodes at low temperatures to manufacture multilayer piezoelectric actuators.In this work, Li₂CO₃ was added into 0.7BiFeO3?0.3BaZr0.02Ti0.98O3?0.01molMnO₂ (70BFBTMn) piezoelectric ceramics to reduce their sintering temperatures. 70BFBTMn ceramics were sintered by a conventional solid reaction method, and their structural, dielectric, piezoelectric and ferroelectric properties were studied. These results indicate that 0.5% (mole) Li₂CO₃ is the optimized content and it can reduce the sintering temperature by 100°C, making the possibility of the piezoelectric ceramics cofiring with Ag electrodes at low temperatures to manufacture multilayer piezoelectric actuators.

Ceramic samples of BiFeO₃-based perovskite solid solutions with the highly ordered complex perovskites PbFe1/2Sb1/2O₃(PFS) and SrFe1/2Sb1/2O₃ (SFS) were obtained using high-pressure synthesis at 4–6 GPa. Mössbauer studies revealed that BiFeO₃-SFS compositions are characterized by a larger compositional inhomogeneity as compared to BiFeO₃-PFS ones. In line with this result, concentration dependence of the magnetic phase transition temperature TN for BiFeO₃-SFS compositions is close to the TN(x) dependence for BiFeO₃solid solution with disordered perovskite PbFe1/2Nb1/2O₃(PFN). In contrast to this TN(x) dependence for BiFeO₃-PFS compositions nicely follows the theoretical TN(x) dependence calculated for the case of the ordered distribution of Fe3+ and non-magnetic Sb5+ ions in the lattice (chemical ordering).Ceramic samples of BiFeO₃-based perovskite solid solutions with the highly ordered complex perovskites PbFe1/2Sb1/2O₃(PFS) and SrFe1/2Sb1/2O₃ (SFS) were obtained using high-pressure synthesis at 4–6 GPa. Mössbauer studies revealed that BiFeO₃-SFS compositions are characterized by a larger compositional inhomogeneity as compared to BiFeO₃-PFS ones. In line with this result, concentration dependence of the magnetic phase transition temperature TN for BiFeO₃-SFS compositions is close to the TN(x) dependence for BiFeO₃solid solution with disordered perovskite PbFe1/2Nb1/2O₃(PFN). In contrast to this TN(x) dependence for BiFeO₃-PFS compositions nicely follows the theoretical TN(x) dependence calculated for the case of the ordered distribution of Fe3+ and non-magnetic Sb5+ ions in the lattice (chemical ordering).

BiFeO3基无铅压电陶瓷常因漏电流较大而压电性能欠佳, 然而, 改善其绝缘性和电性能的方法都较为复杂, 限制了其产业化生产与应用。本工作在不针对0.7BiFeO3-0.3BaTiO3陶瓷进行组分掺杂以及气氛烧结的条件下, 仅通过简单的原料预处理(改变Fe2O3原料的干燥时间)即实现了其高绝缘性与高压电性能。研究结果表明,0.7BiFeO3-0.3BaTiO3陶瓷的晶粒尺寸和绝缘性随Fe2O3原料干燥时间的增加而增大, 同时其电性能及温度稳定性也随之增强。当原料干燥时间为192 h时, 样品晶粒尺寸最大, 绝缘性最好, 同时其压电性能(d33=203 pC/N,kp=0.33)和居里温度(Tc=460 ℃)也达到最佳。这为今后BiFeO3基陶瓷压电性能的研究提供了一个新思路。

BiFeO₃ thin films were prepared using the chemical solution route on Pt/TiO₂/SiO₂/Si(100) substrates under different crystallization kinetics. The crystallization kinetic effects on the dielectric and electrical properties have been investigated. These properties included dielectric permittivity, electric modulus, electrical conductivity measurements as a function of the temperature (300–525 K) and frequency (10²–10⁶ Hz), and leakage current measurements electric field range ± 30 kV/cm at room temperature. The differences observed in conductivity and current density of the BiFeO₃ films were discussed in terms of possible defects induced by the crystallization kinetic. An anomalous relaxor-like dielectric behavior characterized by a broad maximum in the real dielectric permittivity as a function of temperature and the low-frequency dielectric dispersion has been observed. The nonexpected peaks in the real permittivity were accompanied by increasing at least four orders in the conductivity’s magnitude at high temperatures. The origin of the relaxor-like dielectric anomalies is discussed, suggesting that the dielectric permittivity peaks are artifacts due to carrier migration correlated to the onset of the Maxwell–Wagner effect.BiFeO₃ thin films were prepared using the chemical solution route on Pt/TiO₂/SiO₂/Si(100) substrates under different crystallization kinetics. The crystallization kinetic effects on the dielectric and electrical properties have been investigated. These properties included dielectric permittivity, electric modulus, electrical conductivity measurements as a function of the temperature (300–525 K) and frequency (10²–10⁶ Hz), and leakage current measurements electric field range ± 30 kV/cm at room temperature. The differences observed in conductivity and current density of the BiFeO₃ films were discussed in terms of possible defects induced by the crystallization kinetic. An anomalous relaxor-like dielectric behavior characterized by a broad maximum in the real dielectric permittivity as a function of temperature and the low-frequency dielectric dispersion has been observed. The nonexpected peaks in the real permittivity were accompanied by increasing at least four orders in the conductivity’s magnitude at high temperatures. The origin of the relaxor-like dielectric anomalies is discussed, suggesting that the dielectric permittivity peaks are artifacts due to carrier migration correlated to the onset of the Maxwell–Wagner effect.

采用传统固相烧结法合成了0.7BiFeO3-0.3BaTiO3+x%Sb2O3(质量分数)陶瓷(BFO-BTO+xSb, x=0.00~0.20), 研究了Sb2O3掺杂对BFO-BTO陶瓷的晶相结构、介电、导电以及压电和铁电性能的影响, 并对影响机理进行探讨。结果表明: Sb掺杂导致陶瓷的晶体结构由伪立方相向菱形相转化。Sb的B位取代增加了BFO-BTO+xSb陶瓷的铁电弛豫性, 降低高温损耗, 并使居里温度Tc有所降低。导电特性的研究表明, Sb掺杂改变了V×O和Fe2+的浓度, 降低了电导率, 但没有改变陶瓷的导电机制, 其主要载流子是氧空位。Sb掺杂量x=0.05时, BFO-BTO+xSb陶瓷表现出最佳的综合电性能: d33=213 pC/N, kp=28.8%, Qm=38, Tc=520 ℃, Pr =24.7 μC/cm2。

通过模板法制备钒酸铋(BiVO₄)薄膜, 用溶胶-凝胶法制备铁电材料铁酸铋(BiFeO₃)并对BiVO₄进行修饰, 以半导体复合的方式提高BiVO₄的光电化学性能。电化学测试结果表明, 经BiFeO₃修饰后, BiVO₄薄膜的光电化学性能有所提高, 其中经BiFeO₃旋涂5次后的BiVO₄薄膜具有最优的光电化学性能, 光电流密度达到0.72 mA·cm^-2, 较未修饰样品提高了67.4%。利用外场极化调节能带弯曲可以显著地提高BiVO₄/nBiFeO₃铁电复合物的光电化学性能, 复合物经正极化20 V电压处理后的光电流密度最高为0.91 mA·cm^-2, 比BiVO₄薄膜提升了1倍以上, 具有良好的光电化学性能。BiFeO₃与BiVO₄复合后有利于形成异质结, 促进光生电子、光生空穴的产生与分离, 并且外场极化调节能带弯曲使光生电荷加速转移, 是铁电复合物光电化学性能提高的主要原因。

本文通过溶胶-凝胶法制备了BiFeO3@TiO2复合纳米颗粒, 利用透射电镜(TEM)、X射线衍射(XRD)、荧光发光光谱等对纳米颗粒进行表征。研究采用Cell Counting Kit-8(CCK-8)法分别检测了在暗室条件、光照条件以及不同强度的弱稳恒磁场作用下, 用终值质量浓度为50 μg/mL纳米颗粒处理HL60细胞活性, 试验结果表明: 在暗室条件下, 药物质量浓度为50 μg/mL,与HL60细胞共同孵育12 h后, BiFeO3@TiO2复合纳米颗粒随着TiO2外壳厚度增加, 细胞的暗室相对存活率从78%增加到85%; 在光照条件下, 有弱稳恒磁场作用的BiFeO3与TiO2质量比为1∶2的BiFeO3@TiO2复合纳米颗粒对HL60细胞的PDT灭活效率最高达到78%, 弱稳恒磁场环境增强了对HL60细胞的PDT灭活效率, 这为对弱稳恒磁场环境下的光动力疗法治疗白血病肿瘤细胞的临床应用提供了参考。

多铁性材料BiFeO3(BFO)由于具有潜在的磁电耦合效应而备受关注, 但纯相陶瓷的制备始终是一个难点, 部分原因在于对其反应烧结相变规律的认识尚不充分。 高温原位拉曼光谱技术(HT-Raman)是表征复杂的固体相变及反应的有力手段。 首次利用HT-Raman, 研究了不同配比(1∶1, 1.03∶1和1.05∶1)的Bi2O3-Fe2O3在不同升降温速率(10和100 ℃·min-1)下的反应烧结相变过程, 以及降温时反应产物的收缩效应。 结果表明: Bi2O3-Fe2O3反应烧结生成BiFeO3的过程中, 会产生中间过渡相Bi2Fe4O9和Bi25FeO39∶Bi2O3-Fe2O3配比为1.03∶1、 升降温速率较快时, 产物中杂相含量最少, 可见Bi过量及较快的升降温速率能有效抑制杂相的生成。 降温过程中, 发现BFO的A1-1峰位随着温度降低发生蓝移, 且二者呈良好的线性关系, 这说明降温过程中BFO仅因温度变化产生晶格收缩, 并没有结构相变。 此外, 还利用二维X射线衍射(2D-XRD)及背散射电子衍射(EBSD), 表征了烧结产物的相组成及形貌。 XRD结果也显示Bi过量时杂相含量较少, 与拉曼结果一致。 结合2D-XRD和EBSD的结果可知, Bi过量时烧结产物晶粒尺寸较大且均一, 可见快速升降温有利于晶粒的成核与生长。 研究结果可帮助进一步认清反应烧结规律, 并指导纯相BiFeO3基陶瓷的制备。