氧空位对SrBi4Ti4015铁电陶瓷电性能的影响

用高温固相烧结法制备了SrBi4Ti4O15（SBTi）铁电陶瓷,用双氧水浸泡72h进行氧处理的样品与未经过氧处理的样品进行对比研究。样品的介电损耗谱表明：氧处理使SBTi在20℃～300℃温度范围内的介质损耗明显降低,这主要是由于氧处理使样品中氧空位浓度降低引起的。在温度高于300℃时,经过氧处理的样品的介质损耗迅速增大,这是因为氧处理使空穴载流子浓度增大。通过对材料的直流电导与温度关系的Arrhenius拟合,分析了SBTi的导电机理。结果表明,氧处理并未明显改变样品在300℃。650℃温度区域的栽流子激活能,却使其在20℃一300℃范围内的激活能从0．52eV变化到0．71eV。     

氧空位对Fe掺杂ZnO的铁磁性的影响

利用反应磁控溅射法在S i基地生长Zn1-xFexO(x=0.04,0.06,0.08,0.10,0.12)薄膜.X射线衍射结果表明所有样品都具有纤锌矿结构,且C轴择优取向.X射线光电子能谱显示薄膜中的Fe离子为 2价态.磁力显微镜结果表明薄膜具有明显的磁畴花样.磁性测量表明所有在真空下退火的样品都具有室温铁磁性而空气下退火样品具有顺磁性.薄膜中的铁磁性与氧空位有关.     

含氧空位斜钨矿结构PbWO4晶体的第一性原理研究

采用第一性原理模拟计算了完整斜钨矿结构PbWO4晶体的电子结构和含有氧空位斜钨矿结构PbWO4晶体的电子结构．通过对两者进行对比,发现晶体中的氧空位陷获电子形成EF＋心,在禁带中引入一个附加能级,导致在620nm处有一定吸收．提出PbWO4晶体600—800nm吸收带与晶体中的氧空位有关,当晶体中同时含有白钨矿和斜钨矿这两种结构的套构时,由氧空位引起的吸收仍在黄光区．     

Co1-xCrxFe2O4的制备及其析氧性能研究

利用高温固相反应法,使用Fe_3O_4、Co_2O_3和Cr_2O_3为原料,制备了Cr掺杂的Co_(1-x)Cr_xFe_2O_4(x=0.10,0.15,0.20,0.25)粉末,对不同掺杂量的样品使用X射线衍射仪和扫描电子显微镜进行结构和形貌的表征,同时对样品进行了电催化析氧活性测试.结果表明,随着Cr掺杂量的增加,样品的晶格常数逐渐减小.当掺杂量为x=0.1时,样品具有最高的电催化析氧活性,在电流密度为10 mA/cm~2时,其析氧过电位为338 m V,塔费尔斜率为47 mV/dec.     

Bi5TiNbWO15共生铁电陶瓷的介电特性

利用HP4192A低频阻抗分析仪研究了BisTiNbWO15共生铁电陶瓷的介电特性.从介电常数随温度变化谱上(5kHz≤f≤500kHz)观察到,600℃附近的相变峰具有明显的弥散特性,运用修正后的Curie-Weiss定律对该相变峰进行拟合,得到弥散因子γ接近于2,表明弥散程度很高.在200-400.C之间,介电损耗谱出现一个明显的弛豫型过程,通过Arrhenius关系拟合得到弛豫激活能为0.76eV,弛豫时间为5.80x1-13s,通过氧气氛处理和A位Nd掺杂证实了该弛豫行为与氧空位有关.氧气氛烧结和Nd掺杂能有效减少氧空位的浓度,随着氧空位浓度的减少,弛豫激活能增大.     

掺碳氧化锌薄膜的铁磁性

采用磁控溅射方法在Al2O3（0001）和Si（100）衬底上制备掺碳氧化锌薄膜,溅射薄膜时衬底温度为550°C.实验结果显示,制备的掺碳氧化锌薄膜样品在Al2O3（0001）单晶衬底上结晶质量更好.在室温下,所制备的薄膜皆出现铁磁性,且在Si（100）衬底上制备的样品具有更大的饱和磁化值.实验结果表明氧空位缺陷对掺碳氧化锌薄膜的铁磁性起源有很重要的影响.     

快中子辐照直拉硅中V2的退火研究

利用傅立叶红外吸收光谱（FTIR）和正电子湮没技术（PAS）对快中子辐照直拉硅中的双空位（V2）的退火行为进行了研究。实验表明,双空位主要通过捕获VO而消失,因V30与V2有相同的正电子寿命,因此,正电子湮没谱中V2成分比IR吸收谱中V2的消除温度提高大约100℃。     

改性硫氧镁复合墙板抗翘曲变形试验研究

为了改善硫氧镁水泥条板翘曲变形的问题,向硫氧镁水泥掺入改性剂及掺合料,研究了改性剂和掺合料对硫氧镁水泥的影响。试验表明:硫氧镁水泥掺入15%粉煤灰、0.5%柠檬酸和0.5%磷酸,硫氧镁水泥条板并未翘曲变形。     

La空位(La(1-x-y)Yy)2/3Ca1/3MnO3的结构和输运性质研究

用固相反应法制备La（1-x）2／3Ca1／3MnO3（V-LCMO）和（La（0.7-x）Y0.3）2／3Ca1/3MnO3）（V-LY-CMO）（x〈0．15）系列的La空位锰氧化物样品。X射线衍射（XRD）测量分析表明所有的样品均为单相,具有正交对称性（Prima）。体系的晶构参数以及Mn-O键长和Mn-O-Mn键角随空位浓度不同而改变,表明局域Jahn-Teller效应的存在。输运测量表明,不同的空位及空位浓度影响磁电阻效应,在X=0．04时磁电阻值在转变温度‰处达到最大值约为220％,我们认为很大的磁电阻效应与Y部分替代La有关,是双交换作用与Jahn-Teller效应竞争的结果。     

铁离子表面掺杂锐钛矿TiO_2(001)面的第一性原理研究

基于周期性密度泛函理论,本文研究了Fe吸附于锐钛矿TiO2(001)面、替位掺杂表面Ti位,以及在横向晶隙和纵向晶隙内部掺杂的晶体结构变化及形成能,讨论了对应的能带结构及态密度的变化。为与表面氧空位进行对比,计算了氧空位存在条件下的能带结构及态密度。通过形成能的比较发现:Fe在吸附于晶体表面并向体内迁移时,倾向于掺杂在晶体表面晶隙位置。通过对电子结构及态密度的分析发现:Fe在晶体表面晶隙掺杂较表面氧空位掺杂更有利于TiO2光催化氧化效率的提高。     

Structural and dielectric properties of Y2O3-doped Ba0.92Sr0.08Ti0.95Sn0.05O3 ceramics

The structural and dielectric properties of Ba0.92Sr0.08Ti0.95Sn0.05O3 (BSTS) +x (molar ratio, %) Y3+ ceramics are investigated. Combining the lattice parameters and the distortion of crystal lattice, an alternation of substitution preference of Y3+ ion for the host cations in perovskite lattice is found. Owing to Y3+ ion entering the A site, the maximum dielectric constant is 5 627 for 1.25% Y3+-doped samples; when Y3+ ion is more than 1.25%, it tends to occupy the B site in perovskite lattice, causing a drop in the dielectric constant. Owing to the appearance of oxygen vacancy, the optimized dielectric loss is 0.004 for 1.25% Y3+-doped samples. The thermal stability of BSTS ceramics is significantly improved and the Curie temperature shifts to lower value with the amount of Y2O3 increased, making it a superior candidate for capacitor applications.     

Programmed cell death features in apple suspension cells under low oxygen culture

INTRODUCTION A number of abiotic stresses have been shown to induce programmed cell death (PCD) responses in plant cells. High temperatures (e.g. 55 篊) induce nuclear condensation and DNA fragmentation in cultured carrot, cucumber and Arabidopsis cells (McCabe et al., 1997; McCabe and Leaver, 2000), and also mitochondrial cytochrome c release in cucumber cotyledons (Balk et al., 1999). The PCD pathway also appears to be activated by ozone. Ozone induces an oxidative burst with acc…     

Programmed cell death features in apple suspension cells under low oxygen culture

Suspension-cultured apple fruit cells (Malus pumila Mill. cv. Braeburn) were exposed to a low oxygen atmosphere to test whether programmed cell death (PCD) has a role in cell dysfunction and death under hypoxic conditions. Protoplasts were prepared at various times after low oxygen conditions were established, and viability tested by triple staining with fluorescein diacetate (FDA), propidium iodide (PI) and Hoechst33342 (HO342). DNA breakdown and phosphatidylserine exposure on the plasma membrane were observed using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and annexin V binding. About 30% of protoplasts from cells after 48 h under low oxygen showed an increased accumulation of HO342, indicating increased membrane permeability. Positive TUNEL and annexin V results were also only obtained with protoplasts from cells under low oxygen. The results suggest that apple cell death under low oxygen is at least partially PCD mediated, and may explain tissue breakdown under controlled atmosphere (low oxygen) conditions in apple fruit.     

Structure and Dielectric Properties of Sb2O5-Doped ZrO2-SnO2-TiO2 Microwave Ceramics

The microwave frequency band is generally con-sidered in the range of 0.3—3 000 GHz. Its impor-tance is recognizable in the current growth of micro-wave communications systems which make use of thesuperior information density. Many kinds of dielectricmaterials have been developed for microwave applica-tions[1,2]. Among them, solid solution ZrO2-SnO2-TiO2(ZST) has a higher dielectric constant, a highquality factor (Q) value and a lowtemperature coeffi-cient of resonant frequency (TCF). B…     

退火时间对低温烧结AlN陶瓷介电性能的影响

研究了退火时间和碳对低温烧结AlN陶瓷的介电性能,特别是介电常数的影响.结果表明,退火时间通过改变氧在AlN晶格中的扩散过程对介电常数产生极大的影响.随着碳含量的增加介电常数迅速增大,但对介电损耗的几乎不产生影响.     

Ba1-xSrxTiO3（x=0,0.1,0.2,0.3,0.4）陶瓷材料的结构及介电性能的研究

采用传统固相反应方法制备了(Ba1-xSrxTiO3,BST)(x=0,0.1,0.2,0.3,0.4)陶瓷材料,用X射线衍射方法和介电谱方法研究了所制备陶瓷材料的结构和介电性能,结果表明,所制备样品,Sr2+进入BaTiO3后与Ba2+形成了钙钛矿型连续固溶体;随着Sr2+含量的增加,峰位向高衍射角度移动,晶粒尺寸减小,说明Sr2+的掺入抑制了晶粒的生长;BST的系列样品随着温度的升高,介电常数增大,但是随着频率的增大介电常数减小,且峰值随着Sr2+含量的增加都向低温区移动,Sr2+的掺入,有明显的压峰效应,具有弥散相变的特征.     

Synthesis of Ag（Nb0.8Ta0.2）O3 Ceramics Under Different Ambient Conditions

Different ambient conditions for the synthesis of Ag（Nb0.8Ta0.2）O3 ceramics were investi- gated. The Ag（Nb0.8Ta0.2）O3 powder was synthesized at 950 ℃ under different ambient conditions, and then pressed into disks and sintered between 1060 ℃ and 1100 ℃ respectively. Samples were investigated by X-ray diffraction, scanning electron microscopy and dielectric measurement. The results show that perovskite Ag（Nb0.8Ta0.2）O3 powder was easier to be synthesized in air than in vacuum at 950℃. Grain size of ceramic samples sintered in air was uniform （about 1 μm） and its dielectric loss was small for its high density. However, the samples decomposed greatly and ceramics could hardly be densified when sintered in vacuum, Thus,. higher atmospheric pressure and oxygen atmosphere would benifit the synthesis of Ag （Nb0.8Ta0.2）O3, and suppress its decomposition at high temperature.     

Co掺杂ZnO基稀磁半导体材料磁性研究进展

ZnO基稀磁半导体是目前研究的热门课题,其中关于Co掺杂ZnO的磁性研究有很多报道。本文对不同方法及条件制备的Co掺杂ZnO基稀磁半导体的磁性和相应机理进行了归纳总结,分析发现铁磁性可能源于载流子调制、晶格中的氧空位、杂质相、交换作用等。