BiI3修饰Cs3Bi2I9自供能光电化学型探测器制备及其性能

在溶液法合成Cs₃Bi₂I₉前驱体溶液的基础上，采用添加BiI₃修饰Cs₃Bi₂I₉溶液的方法后得到Cs₃Bi₂I₉/BiI₃薄膜并制备出具有自供能特性的Cs₃Bi₂I₉/BiI₃薄膜光电化学型探测器。结果表明，添加的BiI₃以第二相形式存在于Cs₃Bi₂I₉薄膜中，形成两相混合结构。在紫外光(365nm)单色光照射下，Cs₃Bi₂I₉/BiI₃探测器的开关比达到3198，响应度和探测率分别为2.85×10^-3A/W和3.77×10¹⁰Jones...     

铯掺杂提升反梯度结构二维(CMA)2MA8Pb9I28钙钛矿薄膜及太阳电池的性能

相对于3D钙钛矿材料,二维(2D)有机-无机杂化钙钛矿材料具有更好的稳定性.然而由于载流子输运性差, 2D钙钛矿太阳电池效率较低.为了提高2D钙钛矿太阳电池的效率,制备了铯掺杂的具有反梯度结构的二维(CMA)₂MA₈Pb₉I₂₈薄膜.研究结果发现:CsI掺杂能够改善(CMA)₂MA₈Pb₉I₂₈薄膜的形貌、增加晶粒尺寸、降低缺陷态密度,并且提高了(CMA)₂MA₈Pb₉I₂₈钙钛矿薄膜的热稳定性.最后, CsI掺杂浓度为10%时制备(CMA)₂MA₈Pb₉I₂₈钙钛矿太阳电池效率最高,达到了14.67%,相对于未掺杂的电池效率(10.06%)提高了45.8%.     

四方和正交以及单斜相K0.5Na0.5NbO3的结构稳定性和电子结构的第一性原理研究

采用基于密度泛函理论框架下的第一性原理超原胞方法和虚晶近似方法, 在局域密度近似和广义梯度近似下, 对四方和正交以及单斜相K_0.5Na_0.5NbO₃的能量和原子结 构以及电子结构进行了系统的研究. 计算结果表明三种K_0.5Na_0.5NbO₃相的能量差别较小, 这与实验上它们之间容易发生相转化是一致的. 进一步发现单斜相的能量比四方相和正交相低, 说明单斜相结构更加稳定, 并且理论计算的结构参数与实验值符合得很好. 电子结构结果也表明单斜相的键合作用比四方相和正交相键合作用更强, 进一步说明单斜相结构更加稳定. 关键词： 铌酸钾钠 四方相 单斜相 密度泛函理论     

K0.5Bi0.5TiO3—Na0.5Bi0.5TiO3系统铁电陶瓷相界的X射线研究

用X射线衍射方法测定了K_0.5Bi_0.5TiO₃—Na_0.5Bi_0.5TiO₃系统不同组分试样的点阵常数和相变温度,确定了四方-三方相界组成。给出了K_0.5Bi_0.5TiO₃和Na_0.5Bi_0.5TiO₃的多晶X射线衍射数据。 关键词：     

压力诱导CsCu2I3不可逆非晶化和金属化

近年来，压力作用下卤化物钙钛矿的结构和性质引起了科学家们的极大兴趣。然而，对于高压下钙钛矿非晶相的潜在性质和应用仍缺乏深入系统的研究。利用金刚石对顶砧，结合原位高压同步辐射X射线衍射、原位高压拉曼光谱、高压变温电学测量技术，对准一维卤化物钙钛矿CsCu₂I₃在高压下的非晶化行为进行了系统的研究。结果表明：CsCu₂I₃在35.9 GPa以上开始出现可逆的压致非晶化，形成低密度的非晶态Ⅰ相；在更高压力下，发生由低密度到高密度的非晶转变，形成非晶态Ⅱ相，并可以截获至常压条件。进一步的电学实验表明，136.0 GPa时，CsCu₂I₃发生了由绝缘体向金属相的转变，对高压下金属相的非晶态进行卸压电阻测试，发现其金属特性至少可稳定至90.0 GPa。这些结果为进一步探索非晶钙钛矿的潜在性质和应用提供了重要的科学依据。     

多步旋涂过程中CsPbBr3无机钙钛矿成膜机理

在无机钙钛矿太阳能电池的研究中,薄膜制备工艺是影响钙钛矿太阳能电池光电转换效率(PCE)的重要因素之一. CsPbBr₃钙钛矿作为稳定性极好的无机钙钛矿之一,因其前驱体盐(PbBr₂, CsBr)溶解度差异过大,通常采用多步法进行制备.而由于对成膜机理的认识不充分,导致制备的薄膜存在薄膜形貌差、前驱体反应不完全等问题.本文通过旋涂不同次数的CsBr溶液,探究了CsPbBr₃钙钛矿的成膜机理.成膜过程中CsBr扩散进入预先沉积的PbBr₂薄膜完成反应,短暂反应时间使薄膜深层反应不充分而薄膜表面过度反应,CsPb₂Br₅和Cs₄PbBr₆等相伴随CsPbBr₃钙钛矿出现,反复退火形成的薄膜阻挡CsBr扩散加剧了这一现象.适当地延长前驱体的反应时间,能为CsBr扩散及反应提供更充分的空间.基于优化反应时间, CsPbBr₃钙钛矿薄膜形貌得到改善、其晶粒尺寸得到提升,钙钛矿薄膜...     

Ba(Mg1/3Nb2/3)O3电子结构第一性原理计算及光学性能研究

Ba(Mg_1/3Nb_2/3)O₃ (BMN)复合钙钛矿陶瓷具有高介电常数和高品质因子等介电性能, 预示了其在光学领域的应用前景. 本文采用第一性原理方法计算了BMN的电子结构, 对其本征光学性能进行分析和预测. 对固相合成六方相BMN的XRD 测试结果进行Rietveld精修(加权方差因子R_wp=6.73%, 方差因子R_p=5.05%), 在此基础上建立晶体结构模型并对其进行几何优化. 运用基于密度泛函理论(DFT)的平面波赝势方法, 对六方相BMN晶体模型的能带、态密度和光学性质进行理论计算. 结果表明BMN的能带结构为间接带隙, 禁带宽度E_g=2.728 eV. Mg-O和Ba-O以离子键结合为主, Nb-O以共价键结合为主, 费米面附近的能带主要由O-2p和Nb-4d 态电子占据, 形成了d-p轨道杂化. 修正带隙后, 计算了BMN沿[100]和[001]方向上的复介电函数、吸收系数和反射率等光学性质. 结果表明, BMN近乎光学各向同性, 在可见光区, 其本征透过率为77%< T <83%, 折射率为1.91< n <2.14, 并伴随一定的色散现象. 实验测试结果与理论计算结果相吻合.     

新型混合离子-电子导体Sm0.9Ca0.1Al1-xMnxO3-δ的制备及其电性能研究

采用有机凝胶法结合固相烧结技术制备了单相的Sm_0.9Ca_0.1Al_1-xMn_xO_3-δ（SCAM, x=0.1—0.5）新型混合离子-电子导体.通过TG-DTA,XRD和直流四引线法研究了凝胶前驱体的热分解和相转化过程、烧结体的结构、相稳定性、导电性能及其电输运机理.结果表明,凝胶前驱体在900℃焙烧5h可以形成完全晶化的四方钙钛矿相纳米粉体 关键词： 混合离子-电子导体 3')" href="#">SmAlO₃ 有机凝胶法 电导率     

溶胶-凝胶法制备Sr2Bi4Ti5O18薄膜及其铁电性能研究

采用溶胶-凝胶法,在氧气氛中和层层晶化的工艺条件下,成功地制备了沉积在Pt/Ti/SiO₂/Si(100)衬底上的铁电性能优良的Sr₂Bi₄Ti₅O₁₈ (SBTi)薄膜,并研究了SBTi薄膜的微结构、表面形貌、铁电性能和疲劳特性.研究表明：薄膜具有单一的层状钙钛矿结构，且为随机取向；薄膜表面光滑，无裂纹，厚度约为725nm；铁电性能测试显示较饱和、方形的电滞回线，当外电场强度为275kV/cm时 关键词： 溶胶-凝胶法 铁电薄膜 2Bi₄Ti₅O₁₈')" href="#">Sr₂Bi₄Ti₅O₁₈     

Zr4+掺杂对Er3+/Yb3+共掺NaYF4微晶晶相和发光性能的影响

采用油酸辅助的水热法制备了Er³⁺/Yb³⁺共掺NaYF₄微晶,通过在反应体系中引入Zr⁴⁺离子,实现了NaYF₄微晶的晶相控制和上转换发光增强。X-射线衍射和扫描电镜结果表明：Zr⁴⁺离子的引入能够明显加快立方相α-NaYF₄向六方相β-NaYF₄的相转变过程。当Zr⁴⁺离子的引入摩尔分数为5%时,获得了纯的六方相β-NaYF₄微晶。Er³⁺/Yb³⁺共掺NaYF₄微晶在980 nm激光泵浦下,观察到强的上转换绿光和红光发射,且上转换发光强度随着Zr⁴⁺离子添加量的增加逐渐增大。     

Optical spectroscopy of Ca3Sc2Si3O12, Ca3Y2Si3O12 and Ca3Lu2Si3O12 doped with Pr

The silicates Ca₃Sc₂Si₃O₁₂, Ca₃Y₂Si₃O₁₂ and Ca₃Lu₂Si₃O₁₂, both undoped and doped with Pr³⁺ ions, have been synthesized by solid-state reaction at high temperature. The luminescence spectroscopy and the excited state dynamics of the materials have been studied upon VUV and X-ray excitation using synchrotron radiation. All doped samples have shown efficient 5d-4f emission upon direct VUV excitation of 5d levels, but only Ca₃Sc₂Si₃O₁₂:Pr³⁺ shows luminescence upon interband VUV or X-ray excitation. The VUV excited emission spectra of Ca₃Y₂Si₃O₁₂:Pr³⁺ and Ca₃Lu₂Si₃O₁₂:Pr³⁺ show features attributed to emission from two distinct sites accommodating the Pr³⁺ dopant. The decay kinetics of the Pr³⁺ 5d-4f emission in Ca₃Sc₂Si₃O₁₂:Pr³⁺ upon VUV excitation across the band gap are characterized by decay times in the range 25-28 ns with no significant rise after the excitation pulse. They appear to be faster upon X-ray irradiation than for VUV excitation. Weak afterglow components are attributed to defect luminescence.     

Multilayer Bi1.5Zn1.0Nb1.5O7/Ba0.6Sr0.4TiO3/Bi1.5Zn1.0Nb1.5O7 thin films for tunable microwave applications

Bi_1.5Zn_1.0Nb_1.5O₇/Ba_0.6Sr_0.4TiO₃/Bi_1.5Zn_1.0Nb_1.5O₇ tunable multilayer thin film has been fabricated by pulsed laser ablation and characterized. Phase composition and microstructure of multilayer films were characterized by X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The film has very smooth surface with RMS roughness of 1.5-2 nm and grain size of 100-150 nm. Total film thickness has been measure to be 375 nm. The BZN thin films at 300 K, on Pt(1 1 1)/SiO₂/Si substrate showed zero-field dielectric constant of 105 and dielectric loss tangent of 0.002 at frequency of 0.1 MHz. Thin films annealed at 700 °C shows the dielectric tunability of 18% with biasing field 500 kV/cm at 0.1 MHz. The multilayer thin film shows nonferroelectric behavior at room temperature. The good physical and electrical properties of multilayer thin films make them promising candidate for tunable microwave device applications.     

La0.67Ca0.33MnO3薄膜皮秒光电效应

在1064 nm波长脉冲激光（脉宽25 ps）的照射下，钙钛矿氧化物薄膜La0.67Ca0.33MnO3/SrTiO3具有超快光电效应，对激光脉冲显示ps量级的响应时间，上升沿响应时间300 ps，半高宽700 ps，同时，对激光能量的响应灵敏度为500 mV/mJ。     

Structure and magnetic order in La0.7Ca0.3Mn0.5Co0.5O3 and La0.8Sr0.2Mn0.5Co0.5O3 perovskites

In this paper we report the study of the perovskites La_0.7Ca_0.3Mn_0.5Co_0.5O₃ and La_0.8Sr_0.2Mn_0.5Co_0.5O₃ by neutron powder diffraction at various temperatures and magnetization measurements in zero applied field and at low cooling regimes. The replacement of half Mn by Co in La_0.7Ca_0.3MnO₃ and La_0.8Sr_0.2MnO₃ destroys their long-range ferromagnetism exhibiting a cluster glass ferromagnetic order similar to the one observed in many cobaltites.     

合成反铁磁Ni81Fe19/Co90Fe10/Ru/Co90Fe10/Ni81Fe19的研究

采用直流磁控溅射方法制备了一系列的合成反铁磁及以其为自由层的自旋阀.研究发现,在Ni₈₁Fe₁₉与Ru层之间插入适当厚度的Co₉₀Fe₁₀层后,可有效地提高合成反铁磁两磁性层间的反铁磁耦合强度,得到具有饱和场H_s更高、饱和磁化强度M_s更低、热稳定性更好的合成反铁磁.另外,以这种合成反铁磁作自旋阀的自由层时,可有效提高自旋阀的稳定性. 关键词： 合成反铁磁 退火 自旋阀     

Depolarization currents in the Na0.5Bi8.5Ti2Nb4O27 and Na0.5Bi8.5Ti2Ta4O27 layered ferroelectrics

The influence of the prehistory on the electrical properties of layered ferroelectrics is investigated. It is established that the heating of short-circuited samples of the nonpolarized ceramic material Na_0.5Bi_8.5Ti₂Nb₄O₂₇ leads to the appearance of maxima of the current at temperatures below the Curie point only in the case of preliminary ageing of the samples. Original Russian Text ? A.I. Burkhanov, Yu.V. Kochergin, K. Bormanis, A. Kalvane, M. Dambekalne, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 7, pp. 1393–1394.     

X-ray study of phase transitions in the system of solid solutions K2Pb4Nb10O30-Na2Pb4Nb10O30-K6W4Nb6O30

Boundaries of morphotropic phase transitions region in the system of solid solutions K₂Pb₄Nb₁₀O₃₀-Na₂Pb₄Nb₁₀O₃₀-K₆W₄Nb₆O₃₀ with the structure of the tetragonal tungsten bronze have been specified. Presence of the second morphotropic phase transition, perpendicular to the first one has been revealed. The temperature dependences of the structural parameters of some compounds have been investigated. The compounds with high values of Curie temperatures and working temperatures have been obtained.     

Appearance of an inhomogeneous superconducting state in La0.67Sr0.33MnO3-YBa2Cu3O7-La0.67Sr0.33MnO3 trilayers

An experimental study of proximity effect in La_0.67Sr_0.33MnO₃-YBa₂CU₃O₇-La_0.67Sr_0.33MnO₃ trilayers is reported. Transport measurements on these samples show clear oscillations in critical current (I _c) as the thickness of La_0.67Sr_0.33MnO₃ layers (d _F) is scanned from ∼50 ? to ∼ 1100 ?. In the light of existing theories of ferromagnet-superconductor (FM-SC) heterostructures, this observation suggests a long range proximity effect in the manganite, modulated by its weak exchange energy (∼2 meV). The observed modulation of the magnetic coupling between the ferromagnetic LSMO layers as a function of d _F, also suggests an oscillatory behavior of the SC order parameter near the FM-SC interface.      

Incommensurate modulations in Ba2TiSi2O8, Sr2TiSi2O8, and Ba2TiGe2O8

Incommensurate modulations in Ba₂TiSi₂O₈, Sr₂TiSi₂O₈, and Ba₂TiGe₂O₈ are compared based on their corresponding electron diffraction patterns. The dependence of the modulations on chemical composition provides a suitable model system for the investigation of incommensurations in framework structures using high-resolution transmission electron microscopy (HRTEM). A widening of quantitative HRTEM utilising the concept of rigid units is proposed allowing for a determination of atomistic displacements responsible for the formation of incommensurately modulated structures.     

Electrical transport and superconductivity in the Al2O3-Bi2Sr1.8Ca1.2Cu2Oy and MgO-Bi2Sr1.8Ca1.2Cu2Oy composites

We have measured the resistivities of Al₂O₃-Bi₂Sr_1.8Ca_1.2Cu₂O_y and MgO-Bi₂Sr_1.8Ca_1.2Cu₂O_y composites with the nominal Bi₂Sr_1.8Ca_1.2Cu₂O_y volume fraction, ₂₂₁₂, ranging from 0.15 to 1.00. For the Al₂O₃-Bi₂Sr_1.8Ca_1.2Cu ₂O_y composites, we find for the samples with ₂₂₁₂≥0.6 that the superconducting transition temperature, T_c, is not disturbed by the addition of Al₂O₃. For ₂₂₁₂<0.3, no zero-resistivity state is observed. For the MgO-Bi₂Sr_1.8Ca_1.2Cu₂O_y composites, T_c is barely disturbed for the samples with ρ₂₂₁₂≥0.7. No superconducting state is observed for the samples with ρ₂₂₁₂<0.35. The variation of (300 K) with ρ₂₂₁₂ indicates a three-dimensional percolating Bi-Sr-Ca-Cu-O matrix occurring at ρ₂₂₁₂≈0.19 and ≈0.15 in Al₂O₃-Bi₂Sr_1.8Ca_1.2 Cu₂O_y and MgO-Bi₂Sr_1.8Ca_1.2Cu₂O_y, respectively. Both resistivity and magnetization measurements suggest that the reactions of Bi₂Sr_1.8Ca_1.2Cu₂O_y with MgO are weaker than with Al₂O₃.