固相-熔盐法非平衡骤热骤冷工艺制备高纯BiFeO<sub>3</sub>及性能

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吴星, 栗海峰, 周金玲, 霍敏锋, 程呈, 沈绪根, 严春杰. 固相-熔盐法非平衡骤热骤冷工艺制备高纯BiFeO₃及性能 . 无机材料学报, 2014, 29(11): 1151-1155
WU Xing, LI Hai-Feng, ZHOU Jin-Ling, HUO Min-Feng, CHENG Cheng, SHEN Xu-Gen, YAN Chun-Jie. Fabrication and Properties of Highly Pure BiFeO₃ Using A Method of Solid State Reaction-molten Salt Synthesis with Non-equilibrium Process . Journal of Inorganic Materials, 2014, 29(11): 1151-1155 复制到剪切板

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固相-熔盐法非平衡骤热骤冷工艺制备高纯BiFeO₃及性能

吴星, 栗海峰, 周金玲, 霍敏锋, 程呈, 沈绪根, 严春杰

纳米矿物材料及应用教育部工程研究中心(中国地质大学), 中国地质大学(武汉) 材料与化学学院, 武汉430074

通讯作者: 栗海峰, 副教授. E-mail:254510369@qq.com

作者简介: 吴星(1990-), 男, 硕士研究生. E-mail:1214927579@qq.com

基金:纳米矿物材料及应用教育部工程研究中心基金(CUGNGM20135); 全国大学生创新训练项目(201210491018);

摘要

采用固相-熔盐法非平衡骤热骤冷工艺(SSR-MSS-SHCN)制得粒径分布均匀、高纯度的BiFeO₃粉体。通过XRD、FT-IR、TG-DSC、VSM及SEM等对样品物相结构、性能及形貌进行表征。结果表明, 骤热骤冷的非平衡工艺更有利于提高BiFeO₃纯度。单一的固相法或熔盐法采用骤热骤冷非平衡工艺合成的产物均含有Bi₂₅FeO₃₉和/或Bi₂Fe₄O₉杂相。固相-熔盐法骤热骤冷非平衡工艺制得了几近单相的高纯度BiFeO₃粉体。高纯度BiFeO₃粉体磁性能室温呈反铁磁性, 而低温呈弱铁磁性和/或超顺磁性, 而非自旋玻璃态。

关键词: 铁酸铋; 非平衡骤热骤冷工艺; 固相-熔盐法

中图分类号:TB34 文献标志码:A 文章编号:1000-324X(2014)11-1151-05

Fabrication and Properties of Highly Pure BiFeO₃ Using A Method of Solid State Reaction-molten Salt Synthesis with Non-equilibrium Process

WU Xing, LI Hai-Feng, ZHOU Jin-Ling, HUO Min-Feng, CHENG Cheng, SHEN Xu-Gen, YAN Chun-Jie

Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Wuhan 430074, China Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan 430074, China

Abstract

High pure Bismuth ferrite (BiFeO₃) powders were prepared by a solid state reaction-molten salt synthesis method (SSR-MSS method) using shock heating and chilling non-equilibrium process (SHCN process). The structure, morphology and electromagnetic properties were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscope (FTIR), Thermogravimetry-Differential Scanning Calorimetry (TG-DSC) and Vibrating Sample Magnetometer (VSM). The results indicated that SHCN process was better to get higher purity of BiFeO₃ powders than conventional equilibrium process (C process), but still has a certain number of impurity phases like Bi₂₅FeO₃₉ and/or Bi₂Fe₄O₉ as found in the products prepared by either SSR-SHCN process or MSS-SHCN process. In contrast, single-phase BiFeO₃ powders could be obtained by SSR-MSS-SHCN process. The micro-nanoscale BiFeO₃ powders presented antiferromagnetism, superparamagnetism, and/or weak ferromagnetism behavior at room temperature, but not spin-glass state at low temperature (5 K).

Keyword: BiFeO3; solid state reaction-molten salt synthesis method; shock heating &; chilling non-equilibrium process

Show Figures

多铁性材料因同时具有铁磁有序和铁电有序而在一定温度范围内存在磁电耦合特性, 在信息存储、自旋电子学及传感器等领域颇具潜在应用^{[ 1]}。具有铁电性和反铁磁性的BiFeO₃因具有高的居里温度( T_C~1103 K)^{[ 2]}、高的尼尔温度( T_N~643 K)^{[ 3]}和比较高的自发极化值( P_S~100 μC/cm²)^{[ 4]}而成为可在室温应用的首选磁电材料。

有文献对BiFeO₃晶体结构和磁结构等进行了较为详细的报道, 合成单相BiFeO₃仍然比较困难。然而, 合成单相BiFeO₃对其本征性质研究尤为重要。合成BiFeO₃的方法主要有固相法^{[ 5]}、微乳液法^{[ 6]}、熔盐法^{[ 7]}、水热法^{[ 8]}、共沉淀法^{[ 9]}、自燃烧法^{[ 10]}和溶胶-凝胶法^{[ 11]}等。研究表明, BiFeO₃合成过程极易产生Bi₂₅FeO₃₉或/和Bi₂Fe₄O₉等杂质相, 使用一种方法合成单相BiFeO₃均较困难且工艺不易控制, 通常需采用1~5 mol/L硝酸溶液洗除杂相, 导致产物密度降低, 漏电电流增大, 铁电性能减弱^{[ 12]}。另外, 煅烧温度、保温时间、合成方法和工艺制度都是合成单相BiFeO₃的重要影响因素。

本文报道合成高纯BiFeO₃的新方法新工艺, 即先采用固相法煅烧反应物得前驱物, 再以此前驱物为反应物与一定比例(0.5NaCl+0.5KCl)盐混匀, 经磨细、煅烧、洗涤等步骤熔盐法制备BiFeO₃, 且所有加热及冷却过程均分别采用骤热、骤冷工艺, 该新工艺被称为固相-熔盐法非平衡骤热骤冷工艺。通过对产物表征及性能测试, 证明产物为高纯几近单相BiFeO₃粉体。

1 实验方法

原料为Fe₂O₃ (99.9%, Aladdin)、Bi₂O₃ (99.9%, Aladdin)、NaCl (99.5%, Aladdin)、KCl (99.5%, Aladdin)。

1.1 铁酸铋(BiFeO₃)的制备

BiFeO₃粉体采用4种工艺方法制备。

方法(1)固相法骤热骤冷工艺(SSR-SHCN)。称取等摩尔Bi₂O₃、Fe₂O₃混合、磨细磨匀, 加入一定量8wt%的PVA 溶液造粒,240 MPa 压制成 10 mm× 5 mm圆片, 经110℃×24 h烘干, 将其直接置于700℃电炉骤热并保温15~120 min, 待保温结束后直接将样品从电炉取出并骤冷(风冷)至室温, 破碎、磨细后所得即为产物粉体。

方法(2)熔盐法骤热骤冷工艺(MSS-SHCN)。以等摩尔Fe₂O₃及Bi₂O₃为反应物, 配入等摩尔量(0.5NaCl+0.5KCl)混合盐, 待磨细、磨匀后转入带盖刚玉坩埚中, 将其直接置于700℃电炉骤热并保温20~240 min, 待保温结束直接将其从电炉中取出并骤冷(风冷)至室温, 反应物经水煮、磨细、洗涤、干燥得产物粉体。

方法(3)固相-熔盐法非平衡骤热骤冷工艺(SSR-MSS-SHCN)。以方法(1)所得产物为反应物, 重复方法(2)得产物粉体。

方法(4)固相-熔盐法平衡工艺(SSR-MSS-C)。除采用匀速升温、自然冷却外, 重复方法(3)得产物粉体。

1.2 表征及测试

采用X射线衍射仪(Bruker AXS D8-Foucs, 德国Bruker公司)对样品进行物相分析。采用Nicolet 6700傅里叶红外光谱仪测定样品红外光谱图。采用德国NETZSCH STA449 F3同步综合热分析仪测定BiFeO₃粉体TG-DSC曲线。采用精密阻抗分析仪(Agilent 4294A, 美国Agilent公司)测试样品介电性能。采用综合物性测量系统(Physics Property Measurement System, PPMS-9, 美国Quantum Design公司)测量样品磁性能。采用日立SU8010高分辨场发射扫描电镜观察样品颗粒形貌。

2 结果与讨论

2.1 物相分析

图1为固相法骤热骤冷工艺不同保温时间煅烧产物的XRD图谱, 由图可知, 保温15 min时, 产物以BiFeO₃(PDF 82-1254)及Bi₂₅FeO₃₉(PDF 79-0767)相为主, 存少量Bi₂Fe₄O₉(PDF 20-0836)相。随着保温时间延长, Bi₂₅FeO₃₉逐渐减少; 当保温时间延长至120 min时, 产物以BiFeO₃为主相, 仅存少量Bi₂₅FeO₃₉相。图2为熔盐法骤热骤冷工艺不同保温时间煅烧产物XRD图谱, 由图可知, 保温15 min时, 产物除BiFeO₃外, 还存在大量Bi₂₅FeO₃₉相及少量Bi₂Fe₄O₉相。随着保温时间逐渐延长, Bi₂₅FeO₃₉逐渐减少而Bi₂Fe₄O₉逐渐增加。当保温时间延长至240 min时, 产物仍然是BiFeO₃、Bi₂₅FeO₃₉和Bi₂Fe₄O₉三相共存。图1和图2的结果表明, 单一固相法或熔盐法即使采用非平衡骤热骤冷工艺也难以制备高纯度BiFeO₃粉体。

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	图1 固相法骤热骤冷工艺不同保温时间煅烧产物的XRD图谱Fig. 1 XRD patterns of samples prepared by of SSR-SHCN method after being calcinated at 700℃ for different soaking time(1)15 min; (b) 30 min; (c) 60 min; (d) 90 min; (e) 120 min

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	图2 熔盐法骤热骤冷工艺不同保温时间煅烧产物的XRD图谱Fig. 2 XRD patterns of samples prepared by MSS-SHCN method after being calcinated at 700℃ for different soaking time(a) 15 min; (b) 30 min; (c) 60 min; (d) 120 min; (e) 240 min

图3为固相-熔盐法骤热骤冷工艺(SSR-MSS- SHCN)不同保温时间煅烧产物的XRD图谱。由图3可知, 保温15 min时, 产物以BiFeO₃为主晶相, 仅存少量Bi₂Fe₄O₉和Bi₂₅FeO₃₉相。当延长保温时间分别至30、60、90 min, 产物仍以BiFeO₃为主相, 少量Bi₂₅FeO₃₉、Bi₂Fe₄O₉相共存, 且各相相对数量基本保持不变。这是由于体系中BiFeO₃、Bi₂₅FeO₃₉和Bi₂Fe₄O₉三者化学反应平衡所致, 与文献[13]报道一致。当保温时间延长至120 min时, Bi₂Fe₄O₉相和Bi₂₅FeO₃₉相消失, 得到几近单相的高纯BiFeO₃。

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	图3 固相-熔盐法骤热骤冷工艺不同保温时间煅烧产物XRD图谱Fig. 3 XRD patterns of SSR-MSS-SHCN method calcinated samples for different soaking time(a) 15 min; (b) 30 min; (c) 60 min; (d) 90 min; (e) 120 min

图4为固相-熔盐法两种不同工艺煅烧产物的XRD图谱, 对比可知, 温度制度对BiFeO₃合成具有重要影响。由图4 (a)可知, 固相-熔盐法平衡工艺所得粉体除BiFeO₃外, 还含较多Bi₂₅FeO₃₉、Bi₂Fe₄O₉杂相; 而固相-熔盐法非平衡骤热骤冷工艺所得粉体是高纯度BiFeO₃粉体, 不含Bi₂₅FeO₃₉和Bi₂Fe₄O₉杂相。

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	图4 固相-熔盐法平衡(a)与非平衡(b)工艺煅烧产物XRD图谱Fig. 4 XRD patterns of the samples prepared by (a) SSR- MSS-C method; (b) SSR-MSS-SHCN method

2.2 红外光谱分析

图5为固相-熔盐法非平衡骤热骤冷工艺制备高纯BiFeO₃红外光谱图。波数1655.59和1633.18 cm^-1吸收峰对应OH和HOH的伸缩振动和弯曲振动。 548.25和439.72 cm^-1两处吸收峰分别对应于Fe-O伸缩振动和Fe-O弯曲振动, 这是钙钛矿型化合物FeO₆八面体的特征峰^{[ 14, 15, 16]}。由于晶体三方对称性致使Fe-O弯曲振动峰劈裂在409.67 cm^-1出现振动峰。除此之外, 样品没有其他吸收峰。

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	图5 固相-熔盐法骤热骤冷工艺合成BiFeO₃粉体FTIR图谱Fig. 5 FT-IR spectrum of as-synthetized BiFeO₃ by using SSR-MSS-SHCN method

2.3 热分析

图6为空气气氛中以30 K/min升温速度测得的BiFeO₃粉体TG-DSC曲线。由图6可见, 301.58℃始出现一个放热峰并宽化至400℃左右, 这可归属于反铁磁尼尔转变温度( T_N~370℃)加宽现象^{[ 17, 18]}。829.05℃、923.6℃、941.6℃吸热峰分别归因于BiFeO₃的α-β相转变、β-γ相转变、γ-BiFeO₃包晶转变生成Bi₂Fe₄O₉和熔体L。DSC曲线各峰、谷对应温度与文献[18-20]报道的BiFeO₃热分析参数一致, 证实固相-熔盐法非平衡骤热骤冷工艺所制为高纯度BiFeO₃粉体。

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	图6 固相-熔盐法骤热骤冷工艺合成BiFeO₃ TG-DSC曲线Fig. 6 TG-DSC curves of as-synthetized BiFeO₃ by using SSR-MSS-SHCN method

2.4 介电性能

图7为室温下BiFeO₃粉体的介电频谱图, 在1000 Hz到10 MHz频率范围, 介电常数几乎呈线性下降, 在低频和中频范围内出现异常高的介电常数, 此为偶极子的弛豫现象。3 MHz左右出现的一个谐振峰可以归因于外部磁场下离子跳跃, 离子在两个相同势能位置跳跃存在一个固有频率。外部交变电场相当于该固有频率, 所产生的电能转移到振荡离子, 从而使介电损耗值显著增大^{[ 21]}。

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	图7 固相-熔盐法骤热骤冷工艺合成BiFeO₃介电频谱Fig. 7 Dielectric spectra of as-prepared BiFeO₃ by using SSR-MSS-SHCN method

2.5 磁性能

图8为固相-熔盐法非平衡骤热骤冷工艺合成的BiFeO₃粉体磁滞回线。室温300 K下, BiFeO₃粉体具有与BiFeO₃陶瓷相似的 M- H线性依赖关系。由图8(a)显示, Fe³⁺磁矩排列呈反铁磁性。因为BiFeO₃磁结构为长周期(62±2) nm自旋摆线螺旋调制结构^{[ 20]}, 只有BiFeO₃粉体粒径小于此周期才呈现弱铁磁性行为, 而本工作所制BiFeO₃粒径大于此值, 如图9(b)所示。当温度降低至5 K时, BiFeO₃粉体 M- H关系呈明显弯曲S形回线特征(如图8(a)所示)。在318.1 kA/m外场下, BiFeO₃磁化强度 M_s由0.2640 A·m²/kg(300 K)增强至0.4342 A·m²/kg(5 K)(如图8(b)所示)。这可归因于低温下摆线结构变得不可调制, 及对磁序的有害作用被抑制导致弱铁磁性及磁化强度提高^{[ 21]}。另外, 5 K下矫顽力 H_c及剩余磁化强度 M_r均变小, 接近零(如图8(c)所示), 证实BiFeO₃粉体低温下具超顺磁性(SPM)和/或弱铁磁性(WFM)。这与BiFeO₃低温弱铁磁性归因于存在的顺磁Fe^{3+[ 22]}及BiFeO₃低温存在Fe³⁺顺磁性, 且顺磁Fe³⁺可能存于颗粒表面^{[ 8]}的研究结果一致。但是, BiFeO₃低温磁性能与大量文献报道的BiFeO₃低温存在自旋玻璃态(SG)不一致,这可能由于所制BiFeO₃颗粒粒径较大(~5 μm)的缘故。

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	图8 固相-熔盐法骤热骤冷工艺合成BiFeO₃磁滞回线Fig. 8 M-H hysteresis loops of as-synthetized BiFeO₃ by using SSR-MSS-SHCN at 5 K and 300 K (a), and insets are the partially enlarged curves at 300 K (b) and 5 K (c), respectively

2.6 扫描电镜(SEM)分析

图9(a)为固相法骤热骤冷工艺制备产物形貌, 粒子呈不规则状, 其粒径大小约5 μm, 少量细小颗粒与较大颗粒有团聚。图9(b)为固相-熔盐法非平衡骤热骤冷工艺合成的BiFeO₃粉体形貌。类球状BiFeO₃颗粒尺寸约5 μm以下且粒径分布均匀、粉体分散性较好。与图9(a)相比, 颗粒表面明显有(0.5NaCl+ 0.5KCl)熔盐溶解修饰的痕迹。

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	图9 SSR-SHCN (a)及SSR-MSS-SHCN (b)煅烧产物SEM照片Fig. 9 SEM images of BiFeO₃ powder prepared by SSR- SHCN method (a) and SSR-MSS-SHCN method (b)

3 结论

1) 非平衡的骤热骤冷工艺比匀速升温、自然冷却的平衡工艺更有效地提高了产物BiFeO₃纯度。

2) 以固相-熔盐法非平衡骤热骤冷工艺制得几近单相的高纯BiFeO₃粉体, 工艺简单、易控。

3) 高纯度BiFeO₃粉体常温呈反铁磁性, 而低温呈弱铁磁性和/或(类)超顺磁性, 而非自旋玻璃态。

参考文献

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[12]	KUMAR M M, PALKAR V R, SRINIVAS K, et al. Ferroelectricity in a pure BiFeO₃ ceramic. Applied Physics Letters, 2000, 76(19): 2764-2766. [本文引用:1] [JCR: 3.794]
[13]	SELBACH S M, EINARSRUD M A, GRANDE T. On the thermodynamic stability of BiFeO₃. Chemistry of Materials, 2008, 21(1): 169-173. [本文引用:1] [JCR: 8.238]
[14]	LUO W, ZHU L, WANG N, et al. Efficient removal of organic pollutants with magnetic nanoscaled BiFeO₃ as a reusable heterogeneous Fenton-like catalyst. Environmental Science & Technology, 2010, 44(5): 1786-1791. [本文引用:1]
[15]	ZHENG X H, CHEN P J, MA N, et al. Synthesis and dielectric properties of BiFeO₃ derived from molten salt method. Journal of Materials Science: Materials in Electronics, 2012, 23(5): 990-994. [本文引用:1] [JCR: 1.486]
[16]	FARHADI S, ZAIDI M. Bismuth ferrite (BiFeO₃) nanopowder prepared by sucrose-assisted combustion method: a novel and reusable heterogeneous catalyst for acetylation of amines, alcohols and phenols under solvent-free conditions. Journal of Molecular Catalysis A: Chemical, 2009, 299(1): 18-25. [本文引用:1] [JCR: 3.187]
[17]	MAZUMDER R, GHOSH S, MONDAL P, et al. Particle size dependence of magnetization and phase transition near TN in multiferroic BiFeO₃. Journal of Applied Physics, 2006, 100(3): 033908-1-9. [本文引用:1] [JCR: 2.21]
[18]	MI J L, JENSEN T N, CHRISTENSEN M, et al. High-temperature and high-pressure aqueous solution formation, growth, crystal structure, and magnetic properties of BiFeO₃ nanocrystals. Chemistry of Materials, 2011, 23(5): 1158-1165. [本文引用:1] [JCR: 8.238]
[19]	CATALAN G, SCOTT J F. Physics and applications of bismuth ferrite. Advanced Materials, 2009, 21(24): 2463-2485. [本文引用:1] [JCR: 14.829]
[20]	SOSNOWSKA I, NEUMAIER T P, STEICHELE E. Spiral magnetic ordering in bismuth ferrite. Journal of Physics C: Solid State Physics, 1982, 15(23): 4835. [本文引用:1]
[21]	GAO F, YUAN Y, WANG K F, et al. Preparation and photoabsorption characterization of BiFeO₃ nanowires. Applied Physics Letters, 2006, 89(10): 102506-1-3. [本文引用:2] [JCR: 3.794]
[22]	LI S, LIN Y H, ZHANG B P, et al. Controlled fabrication of BiFeO₃ uniform microcrystals and their magnetic and photocatalytic behaviors. The Journal of Physical Chemistry C, 2010, 114(7): 2903-2908. [本文引用:1]

2007

14.829

0.0

Advanced Materials. 2007, 19(19):2889-2892

Visible-Light Photocatalytic Properties of Weak Magnetic BiFeO₃ Nanoparticles

F. Gao 1 ,X. Y. Chen 1,3 ,K. B. Yin 1 ,S. Dong 1 ,Z. F. Ren 4 ,F. Yuan 1 ,T. Yu 1,3 ,Z. G. Zou 1,3 andJ.-M. Liu 1,2

1 Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (P.R. China) 2 International Center for Materials Physics, Chinese Academy of Sciences, Shenyang 110015 (P.R. China) 3 Eco-Materials and Renewable Energy Research Center, Nanjing University, Nanjing 210093 (P.R. China) 4 Department of Physics, Boston College, Chestnut Hill, MA 02467 (USA)

... 多铁性材料因同时具有铁磁有序和铁电有序而在一定温度范围内存在磁电耦合特性, 在信息存储、自旋电子学及传感器等领域颇具潜在应用^[1] ...

2004

0.0

... 具有铁电性和反铁磁性的BiFeO₃因具有高的居里温度(T_C~1103 K)^[2]、高的尼尔温度(T_N~643 K)^[3]和比较高的自发极化值(P_S~100 #cod#x003bc ...

2005

0.0

... 具有铁电性和反铁磁性的BiFeO₃因具有高的居里温度(T_C~1103 K)^[2]、高的尼尔温度(T_N~643 K)^[3]和比较高的自发极化值(P_S~100 #cod#x003bc ...

2011

6.378

0.0

... C/cm²)^[4]而成为可在室温应用的首选磁电材料 ...

2007

8.238

0.0

Chemistry of Materials. 2007, 19(22):5431–5436-null

Peculiarities of a Solid-State Synthesis of Multiferroic Polycrystalline BiFeO₃

Matjaz Valant ,* † Anna-Karin Axelsson , and Neil Alford

Department of Materials, Imperial College London, Exhibition Road, SW7 2AZ, London, United Kingdom

Studies of a BiFeO 3 synthesis were performed to identify reasons for the appearance of secondary phases, the Bi 25 FeO 39 - and Bi 2 Fe 4 O 9 -type phases, in the reaction product. X-ray diffraction and microstructural analyses, performed on samples with different concentrations of impurities, showed that the impurities in the starting material crucially influence the phase composition of the reaction product. A fraction of the generated secondary phases strongly depends on the nature and concentration of the impurities. The experimental results can be explained by the theoretical consideration of ternary phase relations between Bi 2 O 3 , Fe 2 O 3 , and an impurity oxide. Single-phase polycrystalline BiFeO 3 was synthesized from ultrapure starting oxides. To avoid using the expensive ultrapure oxides, techniques for reducing the fraction of the secondary phases in the reaction products were developed.

... 合成BiFeO₃的方法主要有固相法^[5]、微乳液法^[6]、熔盐法^[7]、水热法^[8]、共沉淀法^[9]、自燃烧法^[10]和溶胶-凝胶法^[11]等 ...

2007

2.21

0.0

... 合成BiFeO₃的方法主要有固相法^[5]、微乳液法^[6]、熔盐法^[7]、水热法^[8]、共沉淀法^[9]、自燃烧法^[10]和溶胶-凝胶法^[11]等 ...

2007

8.238

0.0

Chemistry of Materials. 2007, 19(15):3598–3600-null

Rapid Synthesis of Multiferroic BiFeO₃ Single-Crystalline Nanostructures

Jun Chen , † Xianran Xing ,* † ‡ Andrew Watson , § Wei Wang , ‖ Ranbo Yu , † Jinxia Deng , † Lai Yan , † Ce Sun , † and Xiaobing Chen ‖

Department of Physical Chemistry and State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China, Institute for Materials Research, School of Process, Environmental and Materials Engineering, The University of Leeds, Leeds, United Kingdom, and College of Physics Science and Technology, Yangzhou University, Yangzhou, China

... 合成BiFeO₃的方法主要有固相法^[5]、微乳液法^[6]、熔盐法^[7]、水热法^[8]、共沉淀法^[9]、自燃烧法^[10]和溶胶-凝胶法^[11]等 ...

2006

14.829

0.0

Advanced Materials. 2006, 18(16):2145-2148

Tunable Synthesis of Bismuth Ferrites with Various Morphologies

J.-T. Han 1 ,Y.-H. Huang 1,2 ,X.-J. Wu 3 ,C.-L. Wu 3 ,W. Wei 1 ,B. Peng 1 ,W. Huang 1 andJ. B. Goodenough 2

1 Institute of Advanced Materials, Fudan University, Shanghai 200433, P.R. China 2 Texas Materials Institute, ETC 9.102, The University of Texas at Austin, Austin, TX 78712, USA 3 Department of Materials Science, Fudan University, Shanghai 200433, P.R. China

... 合成BiFeO₃的方法主要有固相法^[5]、微乳液法^[6]、熔盐法^[7]、水热法^[8]、共沉淀法^[9]、自燃烧法^[10]和溶胶-凝胶法^[11]等 ...

... 这与BiFeO₃低温弱铁磁性归因于存在的顺磁Fe^3+[22]及BiFeO₃低温存在Fe³⁺顺磁性, 且顺磁Fe³⁺可能存于颗粒表面^[8]的研究结果一致 ...

2007

7.429

0.0

Progress in Solid State Chemistry. 2007, 35(2):null-null

Preparation and characterization of BiFeO₃ ceramic

... 合成BiFeO₃的方法主要有固相法^[5]、微乳液法^[6]、熔盐法^[7]、水热法^[8]、共沉淀法^[9]、自燃烧法^[10]和溶胶-凝胶法^[11]等 ...

2013

1.913

0.0

Materials Research Bulletin. 2013, 48(2):null-null

synthesis of BiFeO₃ nanoparticles by a low-heating temperature solid-state precursor method

... 合成BiFeO₃的方法主要有固相法^[5]、微乳液法^[6]、熔盐法^[7]、水热法^[8]、共沉淀法^[9]、自燃烧法^[10]和溶胶-凝胶法^[11]等 ...

2008

0.0

... 合成BiFeO₃的方法主要有固相法^[5]、微乳液法^[6]、熔盐法^[7]、水热法^[8]、共沉淀法^[9]、自燃烧法^[10]和溶胶-凝胶法^[11]等 ...

2000

3.794

0.0

... 研究表明, BiFeO₃合成过程极易产生Bi₂₅FeO₃₉或/和Bi₂Fe₄O₉等杂质相, 使用一种方法合成单相BiFeO₃均较困难且工艺不易控制, 通常需采用1~5 mol/L硝酸溶液洗除杂相, 导致产物密度降低, 漏电电流增大, 铁电性能减弱^[12] ...

2008

8.238

0.0

2010

0.0

... 72 cm^-1两处吸收峰分别对应于Fe-O伸缩振动和Fe-O弯曲振动, 这是钙钛矿型化合物FeO₆八面体的特征峰^[14,15,16] ...

2012

1.486

0.0

Journal of Materials Science: Materials in Electronics. 2012, 23(5):990-994 DOI:10.1007/s10854-011-0533-4

Synthesis and dielectric properties of BiFeO₃ derived from molten salt method

1. College of Materials Science and Engineering, Fuzhou University, 2 Xueyuan Road, University Town, Fuzhou, 350108, People’s Republic of China 2. State Key Laboratory Breeding Base of Photocatalysis, Fuzhou University, 2 Xueyuan Road, University Town, Fuzhou, 350108, People’s Republic of China

Abstract BiFeO 3 powder was synthesized in NaCl media at temperature range from 700 to 800 °C, using Bi 2 O 3 and Fe 2 O 3 as raw materials. Effects of calcining temperature and salt ratios on the synthesis of BiFeO 3 powder had been investigated. It was found that NaCl effectively promoted the formation of BiFeO 3 . Almost pure BiFeO 3 phase with a very small amount of Bi 2 Fe 4 O 9 phase was synthesized at 750 °C with salt weight ratios of 1:1. A large amount of BiFeO 3 phase decomposed to Bi 2 Fe 4 O 9 and Bi 25 FeO 39 phase when the temperature was up to 800 °C. In the present method, the calcining temperature played an important role in the formation of BiFeO 3 phase. BiFeO 3 ceramics derived from molten salt method were prepared and exhibited the higher dielectric constant.

... 72 cm^-1两处吸收峰分别对应于Fe-O伸缩振动和Fe-O弯曲振动, 这是钙钛矿型化合物FeO₆八面体的特征峰^[14,15,16] ...

2009

3.187

0.0

Journal of Molecular Catalysis A: Chemical. 2009, 299(1):null-null

Bismuth ferrite (BiFeO₃) nanopowder prepared by sucrose-assisted combustion method: a novel and reusable heterogeneous catalyst for acetylation of amines, alcohols and phenols under solvent-free conditions

... 72 cm^-1两处吸收峰分别对应于Fe-O伸缩振动和Fe-O弯曲振动, 这是钙钛矿型化合物FeO₆八面体的特征峰^[14,15,16] ...

2006

2.21

0.0

... 58℃始出现一个放热峰并宽化至400℃左右, 这可归属于反铁磁尼尔转变温度(T_N~370℃)加宽现象^[17,18] ...

2011

8.238

0.0

Chemistry of Materials. 2011, 23(5):1158–1165-null

High-Temperature and High-Pressure Aqueous Solution Formation, Growth, Crystal Structure, and Magnetic Properties of BiFeO₃ Nanocrystals

Jian-Li Mi , Thomas N. Jensen , Mogens Christensen , Christoffer Tyrsted , Jens E. Jørgensen , and Bo B. Iversen *

Centre for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University , Langelandsgade 140, DK-8000, Aarhus, Denmark *E-mail: bo@chem.au.dk .

In situ synchrotron radiation powder X-ray diffraction (SR-PXRD) was applied to study the formation and growth of BiFeO 3 nanocrystals, revealing that phase pure BiFeO 3 can be obtained in high-temperature, high-pressure aqueous solution using Bi(NO 3 ) 3 and Fe(NO 3 ) 3 ·9H 2 O as precursors and KOH as mineralizer. The method gives a rapid way for preparation of nanomaterials, and the formation of BiFeO 3 can be finished within seconds after its initial nucleation in near-critical aqueous solution. As proof of concept BiFeO 3 nanocrystals were subsequently synthesized in a continuous flow supercritical system and for reference also in autoclaves. High resolution multitemperature SR-PXRD data were measured between 100 and 1000 K with a step size of 100 K. The magnetic properties of both the autoclave and the continuous flow samples are studied.

... 58℃始出现一个放热峰并宽化至400℃左右, 这可归属于反铁磁尼尔转变温度(T_N~370℃)加宽现象^[17,18] ...

2009

14.829

0.0

Advanced Materials. 2009, 21(24):2463-2485

Physics and Applications of Bismuth Ferrite

Gustau Catalan * andJames F. Scott *

Department of Earth Sciences University of Cambridge Downing Street, Cambridge CB2 3EQ (United Kingdom) * Department of Earth Sciences University of Cambridge Downing Street, Cambridge CB2 3EQ (United Kingdom).

> BiFeO 3 is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature. As a result, it has had an impact on the field of multiferroics that is comparable to that of yttrium barium copper oxide (YBCO) on superconductors, with hundreds of publications devoted to it in the past few years. In this Review, we try to summarize both the basic physics and unresolved aspects of BiFeO 3 (which are still being discovered with several new phase transitions reported in the past few months) and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.

1982

0.0

Journal of Physics C: Solid State Physics. 1982, 15(23):4835-null

Spiral magnetic ordering in bismuth ferrite

I Sosnowska, T P Neumaier and E Steichele

Fakultat fur Phys., Tech. Univ. Munchen, Garching, West Germany

New information on the magnetic ordering of the iron ions in bismuth ferrite BiFeO 3 was obtained by a study with a high-resolution time-of-flight neutron diffractometer. The observed splitting of magnetic diffraction maxima could be interpreted in terms of a magnetic cycloidal spiral with a long period of 620+or-20 AA, which is unusual for perovskites.

... 2) nm自旋摆线螺旋调制结构^[20], 只有BiFeO₃粉体粒径小于此周期才呈现弱铁磁性行为, 而本工作所制BiFeO₃粒径大于此值, 如图9(b)所示 ...

2006

3.794

0.0

... 外部交变电场相当于该固有频率, 所产生的电能转移到振荡离子, 从而使介电损耗值显著增大^[21] ...

... 这可归因于低温下摆线结构变得不可调制, 及对磁序的有害作用被抑制导致弱铁磁性及磁化强度提高^[21] ...

2010

0.0

The Journal of Physical Chemistry C. 2010, 114(7):2903–2908-null

Controlled Fabrication of BiFeO₃ Uniform Microcrystals and Their Magnetic and Photocatalytic Behaviors

Shun Li † ‡ , Yuan-Hua Lin * † , Bo-Ping Zhang ‡ , Yao Wang † and Ce-Wen Nan * †

State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, People’s Republic of China, and School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, People’s Republic of China * To whom correspondence should be addressed. E-mail: (Y.-H.L.) linyh@mail.tsinghua.edu.cn ; (C.-W.N.) cwnan@mail.tsinghua.edu.cn .,† Tsinghua University. ,‡ University of Science and Technology Beijing.

Bismuth ferrite (BiFeO 3 ) uniform microcrystals with various morphologies (microspheres and micro/submirocubes) were successfully synthesized by a controlled hydrothermal method. The resulting microstructures were characterized using X-ray diffraction, scanning/transmission electron microscopies and Raman spectroscopy. Possible formation mechanism for BiFeO 3 microcrystals was proposed. UV−vis spectra showed that the optical properties of the microsized BiFeO 3 crystals were strongly related to their shape and size. We further demonstrated the useful photocatalytic activity of these regular-shaped structures as determined by degradation of Congo red under visible-light irradiation (λ > 400 nm). Additionally, magnetic responses were observed to be influenced by the morphology of as-synthesized BiFeO 3 products, and the ferroelectric performance of BiFeO 3 submicrocube was also studied by piezoelectric force microscopy (PFM). Being a multiferroic semiconductor with suitable narrow band gap (∼2.2 eV) and uniform morphologies, these BiFeO 3 microcrystals might be useful for the design of devices combining magnetic, electronic, and optical functionalities.

... 这与BiFeO₃低温弱铁磁性归因于存在的顺磁Fe^3+[22]及BiFeO₃低温存在Fe³⁺顺磁性, 且顺磁Fe³⁺可能存于颗粒表面^[8]的研究结果一致 ...