溶胶-凝胶法制备BiFeO3粉体及其表征

以硝酸铁和硝酸铋为原料,冰醋酸和乙二醇单甲醚为溶剂制备BiFeO3粉体。采用XRD,SEM,EDS,TG-DSC以及FT-IR等手段对产物的物相、形貌、结构等进行分析,研究煅烧温度和保温时间对BiFeO3粉体的影响。结果表明:BiFeO3的最佳煅烧温度为550~600℃,保温时间为0.5~1.5h。另外,在BiFeO3制备过程中对Bi含量进行过量添加处理,发现当Bi过量3%~6%时,制备出的BiFeO3粉体杂相最少。     

BiFeO_3的水热合成、表征及光催化性能研究

以Bi(NO3)3.5H2O和Fe(NO3)3.9H2O为原料,KOH为矿化剂,聚乙二醇6000为分散剂,水热合成了单相BiFeO3粉体,利用X射线衍射、扫描电镜优化了水热合成条件,利用振动样品磁强计测定了BiFeO3的磁滞回线,并对产物进行了光催化降解甲基橙性能的研究。结果表明,200℃条件下反应6h制备的BiFeO3粉体显顺磁性,紫外光照射4h对甲基橙的降解率可达90%。     

水热可控合成多面体BiFeO3颗粒

以Bi(NO)3·5H2O和Fe(NO)3·9H2O为水热反应原料,选择KOH作为矿化剂合成单相BiFeO3.通过调节KOH浓度和升降温速率可控合成了规则的大尺度多面体BiFeO3颗粒.发现高碱浓度有利于合成规则多面体BiFeO3颗粒,合适的水热降温速率是影响高结晶度BiFeO3颗粒合成的重要因素之一.当KOH浓度为6和8 mol/L,降温速率为0.2℃/min时,产物为高结晶度准立方和截角立方颗粒,当降温速率调节为0.1℃/min时,产物为表面粗糙的立方八面体和截角八面体颗粒.当KOH浓度为8 mol/L,降温速率约为2℃/min时,产物为表面粗糙且有孔洞的截角立方颗粒.通过扫描电镜图片观察到其形貌演变过程并解释了大尺度多面体BiFeO3颗粒的形成机制.     

铌酸钠粉体的水热法合成研究

以Nb2O5和NaOH为原料，KOH为矿化剂，在200℃，浓度为1mol／L或2．5mol／L的碱性溶液中用水热法制备了具有正交晶系结构的NaNbO3粉体．采用XRD和FTIR对产物结构进行了表征，用SEM观察了粉体的结晶形貌，用EPMA方法估算了产物的主要化学成分．研究了KOH、表面活性剂以及反应时间等工艺条件对产物形貌和晶体结构的影响．结果表明，在相同温度下，OH^-的摩尔浓度及反应时间是影响产物结构和形貌的关键因素．利用透射电镜（TEM）和电子衍射（EDS）发现合成的NaNbO3晶粒中存在超结构．     

聚丙烯酰胺凝胶法合成BiFeO_3纳米颗粒

采用一种新的聚丙烯酰胺凝胶法制备了BiFeO3纳米颗粒.以无机盐溶液为原料,通过加入丙烯酰胺使溶液成胶;在溶液成胶过程中,丙烯酰胺聚合形成高分子网络骨架,为粒子提供生长的空间.实验表明,以EDTA作为络合剂可以获得高纯BiFeO3粉体.同时发现,在前驱体溶液中添加适量的葡萄糖,可有效抑制凝胶体在干燥过程中发生剧烈塌缩,对提高粉体的质量起到重要作用.SEM观察显示,制得的BiFeO3粉体的粒度分布均匀,颗粒近似呈球形,颗粒间无粘连团聚现象.DSC分析表明,样品的反铁磁和铁电相变温度分别为370和830℃.电滞回线和磁滞回线测量结果表明,样品在室温下具有明显的铁电性和弱铁磁性.     

溶剂热合成纳米锡酸铅粉体的研究

采用溶剂热法合成出锡酸铅(PbSnO3)粉体。并用XRD和SEM对粉体的晶体结构和微观形貌进行分析和表征。结果表明:当矿化剂浓度KOH为1~3mol/L,反应时间为8h,温度为160℃时,获得粒度均一的锡酸铅粉体。     

溶胶-共沉淀法制备PbSnO_3超细粉末

以Pb(NO3)2和SnCl4·5H2O为原料,采用溶胶一共沉淀法制备超细铅锡复合氧化物PbSnO3.并通过TG/DSC、XRD、SEM和EDS等技术对粉体的形成过程、粒度、形貌等方面进行了表征.结果表明:以NaOH为沉淀剂,并加入一定量的聚乙二醇为分散剂时,所得产物的粒度小,分散性好;PbSnO3的形成过程为:当pH值在8～9范围内,锡离子的水解产物和铅离子发生沉淀反应生成锡酸铅.     

退火工艺对液相自组装法制备BiFeO3薄膜的影响

以Bi(NO3)3·5H2O,Fe(NO3)3·9H2O和柠檬酸为主要原料,采用液相自组装法,以OTS单分子层为模板,在ITO玻璃基片上成功制备了BiFeO3晶态薄膜.研究了退火温度以及保温时间对BiFeO3薄膜的影响.利用DSC/TG对铁酸铋前驱物结晶行为进行了表征,利用XRD和FE-SEM等测试手段对不同退火工艺下...     

BiFeO3粉体样品的制备及其光催化性能的研究

BiFeO3因其具有良好的磁学和电学性质近几年在国内外引起许多科学家的关注。近几年的研究表明，BiFeO3具有合适的禁带宽度（～2，2eV）和良好的化学稳定性，是一种对可见光反应良好的光催化剂，在降解水的有机污染等方面有着极大的用途。与此同时，科学研究者们也发现在太阳能电池和其它光电设备的可见光研究领域里BiFeO3有着极大的用途。理论上讲，如果半导体吸收的光能大于其禁带宽度，能激发产生光生电子和空穴，该半导体就有可能用作催化剂。BiFeO3禁带宽度为2．2eV，对应的吸收阈值约为590nm，从而在可见光FBiFeO3很可能是一种良好的光催化剂。后来许多针对BiFeO3光吸收和光催化性能的实验证明了这种晶体优越的光催化性能，随即，研究者们就如何改变BiFeO3的形貌来提升它的光催化性能展开了讨论。目前来讲，具有特殊形貌的BiFeO3粉体的制备方法成为目前研究的热题。     

微波水热法制备KNbO3粉体及其性能研究（英文）

以氢氧化钾(KOH)和五氧化二铌(Nb2O5)为原料,通过微波水热法在200℃下合成出具有不同晶相、形貌的铌酸钾粉体(KNbO3).当KOH浓度在10~14mol/L时,可以制备出纯相的KNbO3粉体.X射线衍射(XRD)、场发射扫描电镜(FESEM)和透射电镜(TEM)分析可知,KOH浓度由10mol/L增大到15mol/L时,KNbO3粉体由斜方六面体变为正交相,再转变为四方相,对应的形貌也由金字塔状变为棒状,再转变为立方状.当KOH浓度增大到15mol/L时,出现了Nb2O5杂相.常压烧结制备了KNbO3陶瓷,其介电常数达到302,介电损耗为0.023,压电常数达到80 pC/N,平面机电耦合系数为0.17,机械品质因数为70,居里温度为420℃,正交?四方相变温度为223℃.     

Hydrothermal synthesized bismuth ferrites particles: thermodynamic, structural, and magnetic properties

A family of bismuth ferrites (BFO), including Bi2Fe4O9, BiFeO3, and Bi25FeO39 with different morphologies, has been prepared by the hydrothermal method assisted by different alkaline mineralizers. X-ray diffraction refinement calculations are carried out to study the crystal structures of bismuth ferrites. A thermodynamic calculation based on the dissolution-precipitation model was carried out to analyze the hydrothermal synthesis of BFO powders. Magnetic measurements of the obtained bismuth ferrites show different magnetic properties from 5 K to 350 K.     

Hydrothermal synthesis of perovskite bismuth ferrite crystallites with the help of NH4Cl

Bismuth ferrite nanopowders were hydrothermally synthesized with and without NH4Cl for comparison. The effects of NaOH concentration, reaction temperature and reaction time on the product phases and morphologies were studied in detail. Pure BiFeO3 was synthesized in a wide hydrothermal condition with the help of NH4Cl. Especially, it can be synthesized at low temperature of 140 degrees C. X-ray diffraction and Fourier transform infrared spectra revealed the BiFeO3 products had a perovskite structure. Scanning electron microscopy images showed that different BiFeO3 morphologies were formed under different hydrothermal conditions. NH4Cl played a key role in the BiFeO3 formation and BiFeO3 morphologies. Part BiFeO3 samples exhibited weak magnetic properties.     

低碱浓度下水热合成铁酸铋粉体

以硝酸铋为铋源,硝酸铁或氯化铁为铁源,氨水为沉淀剂,在0．06mol／L氢氧化钠的低碱浓度下水热合成了纯相铁酸铋粉体,采用X射线衍射和红外光谱等分析表征,结果表明,所得产物均为钙钛矿结构铁酸铋粉体;SEM观测显示了随温度升高产物形貌的变化过程。以氯化铁为铁源制得粉体的光催化行为利用可见光分光光度计在亚甲基蓝最大吸收波长（664nm）处测试对应染料上清液吸光度值,表征染料脱色程度,结果表明,采用不同的铁源,所得铁酸铋粉体性能基本一致。     

BaMoO4粉体的水热法制备及发光性能研究

利用水热法制备出了不同形貌的白钨矿结构的BaMoO4粉体材料,样品的结构、形貌及光致发光性能利用XRD、Raman、FESEM和PL谱进行了表征,探讨了工艺参数对BaMoO4材料形貌的影响。通过调整反应温度、反应pH值和表面活性剂CTAB浓度可以调控BaMoO4材料的形貌,得到了棱锥状、多面体及树枝状等形貌的BaMoO4材料。BaMoO4样品的室温光致发光谱是由发光中心在约540nm处的单一绿光组成,样品的形貌不同发光强度不同。     

Hydrothermal synthesis and characterization of YVO4-based phosphors doped with Eu3+ ion

Nanocrystalline yttrium orthovanadate (YVO₄): Eu powders with different morphologies were synthesized in basic media by surfactant-assisted hydrothermal process. The structures and optical properties of products were investigated using the X-ray powder diffraction, transmission electron microscopy, and photoluminescence spectroscopy. Results showed that pH value played a key role in the formation of products with different morphologies. The photoluminescence measurement showed that the samples with different morphologies exhibited different properties. The dependence between the fluorescence and the microstructure was discussed.     

Crystal structure and spontaneous magnetism of BiFeO3 powder synthesized by hydrothermal method

Single-phase BiFeO3 powder was successively synthesized by a low-temperature hydrothermal method. Scanning electron microscopy and transmission electron microscopy results showed that BiFeO3 powder had several hundred nanometers to micrometer-sized particles with a broad size distribution. BiFeO3 powder showed weak-ferromagnetic behavior with a small magnetization value (Ms approximately 20 memu/g) at room temperature. Rietveld refinement results for the crystal structure show the displacive disorder of the Fe-site(6a); the Fe-site(6a) splits into two pairs, Fe(1) and Fe(2) displaced by 0.9 angstroms from each other and these sites are partially occupied. Hence the O-site(18b) also splits into the two partially occupied sites forming a distorted FeO6 octahedras. The weak ferromagnetism observed in the hydrothermal BFO powder is ascribed to the displacive disorder of FeO6 octahedras resulting in an incomplete counterbalance between the antiferromagnetic sublattices of the Fe-ions.     

水热法合成Bi25FeO40纳米粉体的研究

本文以Fe(NO3)39H2O和Bi(NO3)35H2O为起始物料,NaOH为沉淀剂和矿化剂,利用水热合成技术制备了Bi25FeO40纳米粉体.利用XRD、SEM和TEM等分析测试手段对所制得Bi25FeO40粉体的物相组成和晶粒形貌等性质进行了研究,并详细讨论了水热反应温度、反应时间和矿化剂浓度等对晶体生长和粉体制备的影响.结果表明,采用这种低温水热技术制备出的产品为纯的Bi25FeO40陶瓷粉体,在微观结构上呈现出三角锥和立方体结构,最佳工艺条件为[Fe]=[Bi]=0.2mol/L,矿化剂[NaOH]=0.5mol/L,在180℃水热反应24h.     

Nonionic surfactant-assisted hydrothermal synthesis of YVO4:Eu3+ powders in a wide pH range and their luminescent properties

YVO₄:Eu³⁺ powders with different morphologies were fabricated by a simple hydrothermal method at 180 °C for 24 h in a wide pH range with the assistance of polyvinylpyrrolidone (PVP) as a nonionic surfactant. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The obtained results showed that the pH value of synthesis solution played a key role in the formation of final products with different morphologies, such as, microspheres, irregular microspheres with grain-like nanoparticles, stone-like structures with regular short nanorods, and smooth rhombohedrons. The PL measurements revealed that the emission intensity of the samples was first decreased, and then increased with increasing the pH value due mainly to the increase in crystallinity and decrease in surface defects.     

柠檬酸自燃烧法制备BiFeO3工艺及性能研究

以柠檬酸做络合剂,硝酸盐做氧化剂,采用柠檬酸-硝酸盐自燃烧法一步合成了具有扭曲菱方钙钛矿结构的BiFeO3粉体.利用X射线衍射(XRD)、差热-热重(DTA -TG)等技术分析了所得BiFeO3粉体,并研究了粉体烧结后BiFeO3陶瓷的相结构和电性能.结果表明,柠檬酸盐溶胶-凝胶法制备的前驱体具有自燃烧特性,自燃烧后B...