锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)O2电极过程动力学研究

采用共沉淀法制备锂离子电池正极材料Li(Ni1/3Co1/3Mn1/3)O2,通过循环伏安法和电化学交流阻抗分析,探讨了锂离子在LiNi1/3Co1/3Mn1/3O2中嵌入和脱出的机制。循环伏安测试结果表明,LiNi1/3Co1/3Mn1/3O2材料结构中不存在John-teller效应,从而抑制了电极材料和电解液之间的副反应。电化学交流阻抗测试结果表明,随着电压的升高Rct(电荷转移电阻)值逐渐减小,而随着循环次数的增加Rct值逐渐增大。     

(Na1/2Bi1/2)TiO3-(Na1/2Bi1/2)(Zn1/3Nb2/3)O3无铅压电陶瓷的介电特性研究

采用固相合成法制备了(1-x)(Na1/2Bi1/2)TiO3-x(Na1/2Bi1/2)(Zn/23Nb2/3)O3(简写为(1-x)NBT-xNBZN)无铅压电陶瓷.研究了该体系陶瓷晶体结构、弥散相变特征与介电弛豫行为.X射线衍射分析表明,所研究的组成均能够形成纯钙钛矿(ABO3)型固溶体.当x≥0.5%摩尔分数时,该体系陶瓷具有三方、四方共存的晶体结构.材料的介电常数-温度曲线显示陶瓷具有两个介电反常峰Tf和Tm.修正的居里-外斯公式较好的描述了陶瓷弥散相变特征,弥散指数随x的增加而增加.x≤0.5%摩尔分数的陶瓷仅在低温介电反常峰Tf附近表现出明显的频率依赖性,随x的增加,陶瓷材料在室温和低温介电反常峰Tf之间都表现出明显的频率依赖性.根据有序-无序转变和宏畴.微畴转变理论探讨了该体系陶瓷介电弛豫特性的机理.     

乙醇共沉淀法制备纳米Li[Ni1/3CO1/3Mn1/3]O2

采用乙醇共沉淀法制备纳米Li[ Ni1/3 Co1/3 Mn1/3] O2材料.采用XRD和SEM对合成材料进行了表征.结果表明:合成材料的粒径为纳米级,平均粒径可达60 nm,此种方法合成材料具有较好的层状结构和较低的阳离子混排程度.在2.8 ～4.3 V(vs Li/Li+)条件下进行充放电测试,结果表明材料具有较好的电化学性能,尤其在高倍率下(10 C),材料的放电性能可以达到大功率用电设备的要求.     

The electrical and structural properties of InyGa1 ? yAs/InxAl1 ? xAs/InP quantum wells with different InAs content

In _x Al_{1 − x} As/In _y Ga_{1 − y} As/In _x Al_{1 − x} As/InP HEMT structures has been investigated with a change in the InAs molar fraction both in the quantum well and the buffer layer. The electrical parameters of the samples are measured at different temperatures. The structural parameters of the layers and the characteristics of the interfaces between them are determined by double-crystal X-ray diffraction. An increase in the Hall mobility and electron concentration, as well as in the structural quality of the samples, is observed alongside an increase in the InAs molar fraction in the quantum well. It is established that high electron mobility is retained at small (to 5%) mismatches between the buffer layer and substrate.     

焙烧温度对Li[Mn1/3Ni1/3CO1/3]O2结构及电化学性能影响

采用碳酸盐共沉淀法制备了Li[Mn1/3Ni1/3Co1/3]O2,研究了前驱体的焙烧温度对材料结构和电化学性能的影响.XRD测试结果表明,800℃下焙烧得到的样品具有较好的层状结构和较低的阳离子混排程度.SEM测试表明合成材料具有球状形貌,平均粒径可达5μm,组成它的一次颗粒粒径平均为200nm.在2.8～4.3V(vs.Li/Li+)0.2C条件下进行充放电测试,800℃下合成的样品的首次放电比容量最高(159.06mAh·g-1),容量损失最小,循环50次后能保持初始放电比容量的95.7;.EIS分析结果表明,800℃焙烧的样品的电化学活性最好.     

Crystal and magnetic structures of the Bi1 ? xSrxFeO3 ? δ and Bi1 ? xAxFe1 ? xMnxO3 (A = Sr, Ca) solid solutions

Bi_{1 − x} Sr _x FeO_{3 − x/2} (I), Bi_{1 − x} Sr _x Fe_{1 − x} MnxO₃ (II), and Bi_{1 − x} Ca _x Fe_{1 − x} Mn _x O₃ (III) solid solutions have been obtained. Their magnetization has been measured by X-ray and neutron diffraction and M?ssbauer spectroscopy. According to the M?ssbauer spectroscopy data, iron ions are in the trivalent state in system I. Near the concentration x ≈ 0.2, rhombohedral distortions (sp. gr. R3c) are transformed into tetragonal (P4/mmm). The symmetry of system II changes at x > 0.2 (R3c → R3c), whereas orthorhombic distortions (R3c → Pbnm) arise in system III at x > 0.2. The magnetic structure is antiferromagnetic (of G type). The samples of systems II and III exhibit weak ferromagnetism at x > 0.2 due to the Dzyaloshinski-Moriya interaction.     

Devitrification characteristics of GexSe1−x glasses

Amorphous Ge_xSe_1?x compounds have been prepared and carefully characterized in the range 0 ? x ? 0.43 (density and micro-hardness measurements and DTA experiments). By heating samples from the amorphous phase, the crystallization process has been investigated for 0.15 ? x ? 0.30. An immiscibility gap in the vitreous region is determined by optical microscopy, from phase-separation observations; moreover, a new metastable crystalline phase appearing as an intermediate step between phase separation and stable GeSe₂ is described.     

On the structure of amorphous GexTe1−x systems

Calculations have been made for the quadrupole splitting of a $\text{3}\text{2}$ spin state of Te¹²⁵ in an amorphous Ge_xTe_1?x system. The results favour the existence of a threefold coordinated black phosphorus structure with an excess of TeTe chains for x-values between o and 0.5; beyond 0.5, threefold coordinated GeTe and an excess of amorphous Ge coexist.     

Composition dependence of the refractive index and its photo-induced variation in the binary glass systems: Ge1−xSex and As1−xSex

The composition dependence of the refractive index and its photo-induced variation have been calculated for the Ge_1?xSe_x and As_1?xSe_x binary glass systems, using the random network model. It is found that the refractive index has a minimum in Ge_1?xSe_x at x = 0.8, while it shows a monotomic increase with increasing As content in As_1?xSe_x glasses. The refractive index of the Ge_1?xSe_x system decreases with illumination and the variation Δn of GeSe₂ is ?0.0316, while the refractive index of the As_1?xSe_x system increases with illumination and the variation of As₂Se₃ is 0.01. These results are in agreement with the experimental results reported by several workers.     

Sb2O3掺杂对Pr6O11压敏电阻微结构和电学性能的影响

采用传统陶瓷工艺制备了Sb2O3掺杂的Pr6O11压敏电阻,并利用现代分析测试技术对其微结构和电学性能进行了研究。样品的相结构比较简单,除了Pr6O11主相外,未发现明显的第二相。样品的相对密度及晶粒尺寸随着Sb2O3掺杂量的提高而降低。非线性系数、压敏电压和晶界电阻都呈现出先降低后增加的趋势,非线性系数最高可达134。分析表明,Sb掺杂不与Pr6O11发生固相反应,其高温分解所产生的蒸汽压会降低Pr6O11压敏电阻的相对密度、晶粒尺寸及势垒高度,电学性能的变化要归结于相对密度、晶粒尺寸及势垒高度的共同作用。     

Structure and photosensitive homojunctions based on Pb1?xSnxSe epitaxial films

The growth of epitaxial films of Pb_{1 − x} Sn _x Se solid solutions of different chemical compositions (x = 0.02–0.05) on freshly cleaved BaF₂(111) faces and the structure of these films have been investigated. Photosensitive p-n homojunctions have been prepared on their basis. The homojunctions are fabricated in a unified technological cycle without breaking vacuum based on n- and p-type films of high structural quality (W _1/2 = 90–100″) that were grown using an additional selenium vapor source. The photosensitivity peak is found to shift to longer wavelengths with an increase in the Sn content in the films grown; this effect is explained by narrowing the band gap with a change in the composition.     

三元铁电单晶Pb(Yb1/2Nb1/2)O3-Pb(Zn1/3Nb2/3)O3-PbTiO3生长及性能表征

采用高温助熔剂法首次成功生长出了Pb(Yb1/2Nb1/2) O3-Pb(Zn1/3Nb2/3) O3-PbTiO3 (PYZNT)三元铁电单晶,并对晶体组分、介电、铁电和压电性能进行了研究.结果表明,晶体为纯三方钙钛矿相,实际组分为0.68PYN-0.22PZN-0.1PT.分别对晶体的介电,铁电和压电性能进行研究.介电常数ε'和介电损耗tanδ对温度和频率表现出典型的弛豫行为.晶体的居里温度TC为80℃.由于反铁电体PYN含量较高,晶体具有非常大的矫顽场,在100kV/cm的外电场条件下极化还不能反转,因而无法得到饱和的电滞回线.在未极化条件下,测得晶体的压电常数d33为78 pC/N.     

Pb(Sc1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3-PbZrO3弛豫铁电晶体的生长及表征

采用高温溶液法生长了准同型相界(MPB)四元弛豫铁电单晶Pb(Sc1/2Nb1/2) O3-Pb(Mg1/3 Nb2/3)O3-PbTiO3-PbZrO3,得到较大尺寸且具有规则外形的立方单晶.研究结果表明所生长的晶体为钙钛矿结构,立方晶粒平整的暴露面均为(001)面;晶体以层状方式生长,生长机制为搭桥生长;所生长晶体的矫顽场Ec～3.52kV/cm,三方四方相变温度Tr-t～104℃,居里温度Tc～149.5℃,压电常数d33～1089 pC/N,剩余极化强度Pr～25.4 μC/cm2;随着频率增加,晶体的相变弥散度减小.     

Pb(In1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3压电陶瓷的介电、铁电和压电性能

采用两步法制备了0.30Pb(In1/2 Nb1/2)O3-(0.70-x)Pb(Ni1/3Nb2/3)O3-xPbTiO3(PIN-PNN-PT,x=0.33,0.35,0.37,0.39)压电陶瓷.研究了PIN-PNN-PT压电陶瓷的相结构、介电、铁电和压电性能.研究表明位于准同型相界(MPB)的组分0.30PIN-0.33PNN-0.37PT具有最佳电学性能,其居里温度TC、压电系数d33、平面机电耦合系数kp、自由介电常数ε二介电损耗tanδ、剩余极化Pr、矫顽场EC分别为200℃、386 pC/N、50;、2692、0.045、34 μC/cm2、18 kV/cm.结果 显示PIN-PNN-PT三元系相比于PNN-PT有更高的居里温度,同时保持了优异的压电性能.     

<001>-取向（1-x）PbMg1/3Nb2/3O3-xPbTiO3单晶电卡效应的组分依赖性

以<001>取向的PMN-0.14PT,PMN-0.17PT,PMN-0.28PT为代表,研究了PT含量对PMN-x PT单晶电卡效应的影响。通过测试单晶的变温电滞回线,计算了PMN-0.14PT,PMN-0.17PT,PMN-0.28PT的电卡效应。计算结果显示PMN-0.14PT,PMN-0.17PT,PMN-0.28PT单晶的电卡效应最大值随着PT含量的增加而增加,在较小的4 k V/mm电场情况下,分别达到1 K,1.17 K,1.96 K。此外,电卡效应峰发生在居里温度介电峰附近,随着PT含量的增加,电卡效应峰越来越尖锐并移向高温方向。     

Study of the relationship between the crystal structure of nanolayers and electrical properties in Al x Ga1? x As/In y Ga1? y As pseudobinary heterostructures by double-crystal X-ray diffraction

The structural parameters of individual layers of samples of a Al _x Ga_1−x As/In _y Ga_1−y As/GaAs pseudomorphic heterostructure have been determined by double-crystal X-ray diffraction. A relationship of the technological parameters of fabrication of heterostructures with their structural and electrical properties is established. The increase in the mobility of the 2D electron gas in the samples under study, caused by the increase in the growth temperature of the Al _x Ga_1−x As spacer layer and the decrease in the time of silicon δ doping from the two sides of the quantum well, correlates well with the degree of the sample structural quality. Original Russian Text ? R.M. Imamov, I.A. Subbotin, G.B. Galiev, 2008, published in Kristallografiya, 2008, Vol. 53, No. 2, pp. 210–213.     

CZTSe/Cd1-xZnxS界面能带结构研究

严重的开路电压损耗是限制铜锌锡硫(硒)薄膜太阳电池性能提升的关键问题,其吸收层和缓冲层界面的能带结构有待进一步优化.针对此问题,本文对CZTSe/Cd1-xZnxS界面的能带结构进行了研究.首先,模拟计算了化学水浴法制备Cd1-xZnxS薄膜所需的溶液体系条件,通过椭偏仪和SEM测试结果分析了不同Cd/Zn比例的Cd1-xZnxS缓冲层形貌、光学特性以及禁带宽度.然后,对CZTSe/Cd1-xZnxS界面进行了XPS测试分析,发现CZTSe/Cd0.9Zn01S界面最为匹配,其导带失调值约为0.3 eV.最后对电池器件进行了制备与测试,得到的CZTSe/Cd0.9Zn0.1S结构的太阳电池比CZTSe/CdS结构具有更高的开路电压,达到了394 mV,转换效率达到了5.78;.     

Effect of annealing on an amorphous GexTe1−x matrix with Te cristallites

Annealing shows very different behaviour for Te crystallites in an amorphous Ge_xTe_1?x matrix as a function of x (x = 0.1 … 0.5). For x ? 0.2, annealing at increasing temperatures increases the number (size) of the Te crystallites with subsequent GeTe + Te crystallization. However for x ? 0.3 there is first a disappearance of Te crystallites, then an appearance of GeTe crystallites, and subsequently GeTe + Te crystallization. Crystallites of either Te or GeTe act as extrinsic defects which add to the intrinsic ones. Activatioon energy decreases (increases) and conductance increases (decreases) as the number of defects increases (decreases). In all cases the final metallic state is obtained only when both GeTe and Te crystallites are present.