铁磁电材料BiFeO_3低温拉曼谱的研究

BiFeO3是少数的在室温时具有磁电耦合效应的铁磁电材料之一,在信息存储、传感器和自旋电子器件等方面都有潜在的应用前景。在4-1100K,通过拉曼散射研究了BiFeO3单晶的性质,讨论了与结构相变相联系的磁有序。     

钙钛矿型纳米BaFeO3的制备、结构表征及铁磁性研究

采用溶胶-凝胶法制备出钙钛矿型纳米BaFeO3粉末,利用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)分析研究了其微观结构及形貌,结果表明:胶体试样经800℃退火处理后,形成了20nm左右的钙钛矿型BaFeO3粉末,其(110)面晶面间距为0.280nm左右,(100)面晶面间距为0.401nm左右.利用振动样品磁强计(VSM)研究了纳米BaFeO3粉末的室温铁磁性能,测量结果表明:在室温条件下,纳米BaFeO3粉末具有完整闭合的磁滞回线,具有较小的矫顽力和较低的饱和磁化强度,呈现出明显的弱铁磁性,且铁磁性随退火温度的变化明显.钙钛矿型纳米BaFeO3的铁磁性主要归因于Fe3 _O_Fe4 之间的氧空位.     

掺铁TiO2纳米薄膜的制备及光催化性能研究

采用溶胶-凝胶提拉法制备了掺铁改性TiO2纳米材料镀膜玻璃,研究了掺铁、PEG用量、镀膜层数等因素对TiO2纳米膜透光率和光催化降解性的影响,并对相关机理进行了探讨。研究发现,掺铁能提升TiO2纳米膜的光催化活性,催化降解速率为不掺铁时的1．38倍;溶胶前驱体中PEG用量为0．1g（0．13wt％）时制取的薄膜具有最佳的光催化活性和较好的透光率,低于或超过这个值,催化降解效果都不理想;镀膜层数为2～5层时,均有较高的透光率,光催化活性依次递增,其中综合效果最佳的为2层镀膜。纳米TiO2镀膜玻璃是一种性能优异的新型自净节能环保材料,在高楼建筑、灯具制造、城市照明系统等领域具有潜在的广泛用途。     

钙钛矿型纳米BaFeO3的制备、结构表征及铁磁性研究

采用溶胶-凝胶法制备出钙钛矿型纳米BaFeO₃粉末,利用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)分析研究了其微观结构及形貌,结果表明：胶体试样经800℃退火处理后,形成了20nm左右的钙钛矿型BaFeO₃粉末,其(110)面晶面间距为0.280nm左右,(100)面晶面间距为0.401nm左右.利用振动样品磁强计(VSM)研究了纳米BaFeO₃粉末的室温铁磁性能,测量结果表明：在室温条件下,纳米BaFeO关键词： 溶胶-凝胶法 3')" href="#">钙钛矿型纳米BaFeO₃ 铁磁性 氧空位     

BiFeO3纳米粉的制备、结构表征及铁磁特性

采用溶胶-凝胶法成功地制备出BiFeO₃纳米粉,利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）测量分析了其结构与形貌,结果发现：胶体经700℃烧结2—25 h后,形成了30 nm左右的较纯相BiFeO₃粉末,该样品为六角晶系,R3-m［166］空间群,晶胞参数为a=b=05580 nm,c=06939 nm,其（101）面晶面间距为0396 nm左右,（ 关键词： 溶胶-凝胶法 3纳米粉')" href="#">BiFeO₃纳米粉 结构表征 铁磁特性     

掺纳米锗氧化硅的发光性能研究

由溶胶/凝胶法制备得到的GeO₂/SiO₂玻璃在700 ℃的条件下经H₂还原,得到具有奇特光致发光性质的Ge/SiO₂玻璃,该玻璃在室温条件下用246 nm（5.01 eV）的光激发时,能发射出很强的 392 nm（3.12 eV）、较强的 600 nm（2.05 eV）和次强的770 nm（1.60 eV） 的荧光.利用X射线衍射（XRD）、X射线光电子能谱（XPS）及透射电镜（TEM）实验证明,该玻璃能够发射3种不 关键词： 2')" href="#">Ge/SiO₂ Ge纳米晶粒 溶胶/凝胶法 光致发光     

Ba掺杂及工艺对BiFeO_3体系结构和磁特性的影响

用溶胶-凝胶+快速热处理方法制备Bi_1-xBa_xFeO_3(BBFO-x,x=0,0.05,0.15)陶瓷材料,研究不同工艺条件和元素掺杂对样品的结构和磁特性的影响,实验结果表明,BBFO-x纯相样品制备工艺要求较高,在工艺条件为800℃下退火450s时,样品具有最好的结构及磁性能;X射线衍射测试表明,Ba元素替代会引起晶格畸变,但没有改变样品的宏观晶格结构;Raman光谱测试进一步证实了样品的纯相结构及Ba元素掺杂对样品结构的影响;此外,Ba元素替代有助于增强样品的磁性,其原因在于掺杂使得原有的长程反铁磁螺旋磁结构受到破坏,同时可能出现Fe离子价态变化,产生自旋耦合,从而在样品中表现出更大的宏观净磁矩,本工作可对开展这一单相多铁材料体系的微观结构以及磁电耦合效应的研究提供很好的实验基础。     

不同前驱体溶液制备BiFeO3薄膜的晶体结构及电学性质研究

BiFeO3 是技术上广泛应用的极为重要的一类多铁性材料.本文采用sol-gel法,在ITO基底上分别采用乙酸和硝酸为溶剂制备纯相BiFeO3薄膜.XRD、电滞回线与介电性分析表明,在退火温度为600℃时,两种溶液均能制备出BiFeO3晶体,相比之下,利用乙酸制备BiFeO3比较容易,且铁电性好.     

纳米复合氧化物LaMnO3的制备及表征

采用溶胶-凝胶法、共沉淀法、非晶态配位法三种不同的方法制备了纳米级的钙钛矿型复合氧化物LaMnO3,并通过XRD、FT-IR、ICP实验技术对所制备的系列纳米催化剂进行了表征。结果表明:3种不同的方法所制备的复合氧化物均形成了ABO3型钙钛矿型结构,都属于纳米颗粒,初步考察了制备条件对复合氧化微粒的形成结构的影响,非晶态配位法制备的LaMnO3平均粒度最小,溶胶-凝胶法制备的样品浓度最高。     

BiFeO3晶体价键电子结构与铁电性质的关系

通过价键电子理论工具,计算得到了钙钛矿型单相多铁材料BiFcO₃"赝立方"顺电相和斜方铁电相价键电子结构,分析了价键电子结构变化时其铁电性的影响.计算结果表明,从顺电相到铁电相,BiFeO₃晶胞中各类化学键的键长和价键电子数变化各异,其中Bi-O键键长变短,价键电子数增多,共价性显著增强,对铁电相的稳定起到至关重要的作用;Fe-O键长呈现变大和变小两种结果,价键电子数都减小,共价性减弱.计算结果与第一性原理计算进行了比较.     

Multiferroic properties of Tb-doped BiFeO3 nanowires

The aim of this study was to investigate the protective role of quercetin and/or l-arginine against the cardiotoxic potency of zinc oxide nanoparticle (ZnO-NP)-induced cardiac infarction. ZnO-NPs (50 nm) were administered orally at either 600 mg or 1 g/kg body weight for 5 consecutive days. The results revealed that co-administration of quercetin and/or l-arginine (each 200 mg/kg body weight) daily for 3 weeks to rats intoxicated by either of the two doses markedly ameliorated increases in serum markers of cardiac infarction, including troponin T, creatine kinase-MB, and myoglobin, as well as increases in proinflammatory biomarkers, including tumor necrosis factor-α, interleukin-6, and C-reactive protein, compared with intoxicated, untreated rats. Each agent alone or in combination also successfully modulated the alterations in serum vascular endothelial growth factor, cardiac calcium concentration, and oxidative DNA damage as well as the increase in the apoptosis marker caspase 3 of cardiac tissue in response to ZnO-NP toxicity. In conclusion, early treatment with quercetin and l-arginine may protect cardiac tissue from infarction induced by the toxic effects of ZnO-NPs.     

铬、钕双掺钆镓石榴石(Cr4+,Nd3+):Gd3 Ga5 O12激光晶体光学性能的研究

用提拉法生长了掺铬、钕的钆镓石榴石(Cr^4 ,Nd^3 ：GGG)自调Q激光品体。报道了室温下的吸收光谱和荧光光谱特性。分析了Cr离子浓度对光谱性质的影响。比较了Cr^4 ：GGG,Nd^3 ：GGG和(Cr^4 ,Nd^3 )：GGG晶体吸收光谱的关系。测量了(Cr^4 ,Nd^3 )：GGG晶体和Nd^3 ：GGG晶体的荧光寿命,它们分别是33μs和250μs。实验表明,(Cr^4 ,Nd^3 )：GGG晶体是一种非常有潜力的自调Q激光晶体,可以实现大功率激光器的小型化和全固态化。     

Investigation of BiFeO3 Multiferroic thin films prepared by metalloorganic chemical vapor deposition

BiFeO₃ thin oriented films are grown on SrTiO₃(001) and ZrO₂(Y₂O₃)(001) substrates by metalloorganic chemical vapor deposition (MOCVD) in the temperature range T= 500–800°C. Iron dipivaloylmethanate Fe(thd)₃ and triphenylbismuth Bi(C₆H₅)₃ are used as volatile precursors. It is shown that the high thermal stability of Bi(C₆H₅)₃ leads to significant deviations of the Bi: Fe ratio in the film from their ratio in the precursor flow. An increase in the residence time of the precursor flow in the reactor makes this ratio close to unity. The film-substrate epitaxial relations are determined. It is found that the film orientation on the ZrO₂(Y₂O₃)(001) substrate changes with increasing temperature. Optical second harmonic generation (SHG) measurements show the presence of ferroelectric ordering in the films. A significant decrease in the Curie temperature due to epitaxial stress is found. At the same time, the magnetization noticeably increases as compared to a BiFeO₃ single crystal.     

掺钕聚甲基丙烯酸甲酯的光学特性

研究了制备的掺钕螯合物Nd(DBM)3Phen材料的吸收光谱、激发光谱、荧光光谱,应用Judd-Ofelt理论计算了该材料的强度参量．分析了钕离子激发态4F3／2的辐射寿命(631 μs)和4F3／2→4IJ′跃迁的受激发射截面和荧光分支比．     

Influence of the Multiplet Levels of Sm3+ and Eu3+ on the Heat Capacity of Multiferroic BiFeO3

Physics of the Solid State - The temperature dependence of the heat capacity of multiferroics BiFeO3, Bi0.90Sm0.10FeO3, and Bi0.90Eu0.10FeO3 has been investigated. It is found that the substitution...     

Cr3+:GGG(Ca,Mg,Zr)和Nd3+,Cr3+:GGG(Ca,Mg,Zr)激光晶体的光谱特性

本文分析了Cr3+:GGG(Ca,Mg,Zr)的荧光谱和吸收谱,测算到Cr3+离子在4T2g-2Eg的能级间距为ΔE≈70cm-1,晶场强度Dq/B=2.50.说明由于GGGa(Ca,Mg,Zr)晶格扩大减弱了晶场,可望实现Cr3+:GGG(Ca,Mg,Zr)室温下的调谐及Nd3+:Cr3+:GGG(Ca,Mg,Zr)中Cr3+→Nd3+能量的转移.最后从理论上阐明了Cr3+在晶体GGG(Ca,Mg,Zr)中的能级结构.     

Correlation of structure and spin–phonon coupling in (La,Nd) doped BiFeO3 films

We studied the effect of structural change on the spin–phonon coupling in doped BiFeO₃ (BFO) films (Bi_0.8La_0.1Nd_0.1FeO₃) grown on SrTiO₃ (001) substrate. The temperature‐dependent Raman studies show phonon anomalies in the vicinity of magnetic ordering temperature T_N owing to the spin–phonon coupling. Doped films exhibit strong anomalies in the line widths of Raman bands around T_N revealing the presence of strong spin–lattice coupling. The modification in structure as a result of A‐site doping in BFO films plays an important role in controlling the nature of spin–phonon coupling. Copyright © 2014 John Wiley & Sons, Ltd.     

Surface State‐Induced Anomalous Negative Thermal Quenching of Multiferroic BiFeO3 Nanowires

Wide‐bandgap semiconductor nanowires with surface defect emission centers have the potential to be used as sensitive thermometers and optical probes. Here, we show that the green luminescence of multiferroic BiFeO₃ (BFO) nanowires shows an anomalous negative thermal quenching (NTQ) with increasing temperatures. The release of trapped carriers from localized surface defect states is suggested as the possible mechanism for the increased green luminescence which was experimentally observed at elevated temperatures. A reasonable interpretation of the photoluminescence (PL) processes in BFO nanowires is achieved, and the activation energies of the PL quenching and thermal hopping are deduced. Negative thermal quenching of BFO nanowires provides a new strategy for optical thermometry at higher temperatures.     

掺杂金属离子对(Eu,Tb)稀土配合物发光性质的影响

合成了以柠檬酸为第一配体、1,10-菲咯啉为第二配体的单核稀土(Eu、Tb)配合物和Tb/Y、Eu/Y按不同比例混合的掺杂稀土配合物。采用红外光谱、紫外光谱、激发和发射光谱等对合成的配合物结构和荧光性能进行了表征。红外光谱表明稀土离子与第一、第二配体进行了配位,配合物的紫外吸收主要是配体的吸收,保持了π→π^* 电子跃迁的特征。激发和发射光谱表明,不发光稀土离子Y³⁺的掺入能显著增强发光稀土离子的光发射强度。