磁场对(C4H9NH3)2(CH3NH3)Pb2I7钙钛矿发光特性调控的研究

(C₄H₉NH₃)₂(CH₃NH₃)Pb₂I₇是一种Ruddlesden-Popper相钙钛矿材料,具有层状结构,层间通过van der Waals力结合,因此可以通过机械剥离的方法,获得其二维薄层。二维(C₄H₉NH₃)₂(CH₃NH₃)Pb₂I₇内束缚激子会自发复合从而表现出强的荧光,其圆极化率、峰位均受磁场调控。在外磁场中,荧光圆极化率与磁场呈线性关系,激子中电子和空穴之间的朗德因子差Δg约为0.43。束缚激子在磁场中受抗磁效应影响,致使其发光峰随磁场增加而红移。     

铁基钙钛矿化合物AFeO3(A=Ca,Sr,Ba)的光催化性能

通过柠檬酸-硝酸盐燃烧法合成了钙钛矿(ABO3)及类钙钛矿(A2B2O5)型化合物BaFeO3,Sr2Fe2O5,Ca2Fe2O5,BaCoO2 93,Sr2Co2O5.用X射线衍射,紫外-可见光分光光度计,红外光谱分析和扫描电镜检测了合成样品.样品经过450℃烧结2 h并在800℃烧结4 h而获得.实验表明:在B位元素相同的情况下,A位元素离子半径越大越容易形成钙钛矿结构.实验中合成的具有钙钛矿或类钙钛矿结构的氧化物具有不同程度的光催化性能.     

面向应用的(K,Na)NbO3基无铅压电陶瓷研究进展

高性能环境友好型（K,Na）NbO₃（KNN）基无铅压电陶瓷是国际上功能陶瓷的重要科学前沿和技术竞争焦点之一。优异的压电性能及其温度稳定性、抗疲劳特性、力学性能以及制备工艺重复性等综合性能是KNN基陶瓷有望得以广泛应用的重要前提,而这些性能与KNN基陶瓷的多层次结构紧密相关。本工作从多层次结构调控的角度出发,总结了KNN基陶瓷压电性能与其温度稳定性、抗疲劳特性、力学性能、制备工艺重复性研究等方面的研究进展以及KNN基陶瓷的应用技术研究进展。最后,就KNN基无铅压电陶瓷的未来发展进行展望。     

(Na,K)NbO_3基无铅压电陶瓷的研究进展

本文主要综述近几年来国内外有关(Na,K)NbO3基无铅压电陶瓷体系的加压固相烧结技术、液相助烧致密化技术、掺杂改性、相结构调控以及相关机理研究方面的研究进展和动向,并展望该陶瓷体系在医疗超声换能器技术方面的应用前景。     

非等摩尔比Sr(Ti,Zr,Y,Sn,Hf)O3-σ高熵钙钛矿氧化物的制备及电学性能研究

本研究采用非等摩尔混料结合两步法烧结制备了一系列非等摩尔比高熵钙钛矿氧化物Sr(Ti,Zr,Y,Sn,Hf)O3-σ。通过XRD、TG-DSC、SEM及TEM分析了其物相转变、表面形貌及晶体结构,并且采用电化学交流阻抗谱(EIS)对其电导率进行分析。研究结果表明Sr(Ti,Zr,Y,Sn,Hf)O3-σ在1480℃左右形成了单相钙钛矿结构,并且各元素分布均匀。在测试温度范围为300~750℃的条件下,Sr(Ti,Zr,Y,Sn,Hf)O3-σ单相钙钛矿结构稳定,其电导率符合阿伦尼乌斯方程,电导机理保持稳定。相较于其他三种高熵钙钛矿氧化物,Sr(Ti0.20Zr0.20Y0.20 Sn0.20Hf0.20)O3-σ(HEOY1)表现出最高的电导率,其750℃的电导率为3.55×10-3S/cm,与文献报道中的高熵钙钛矿氧化物的电导率(2.41×10-3S/cm)相比有较大提升。     

新型硫卤玻璃GeS2-Ga2S3-AgX(X=Cl,Br,I)中的K+-Ag+离子交换

以油酸钾为熔盐,GeS2-Ga2S3-AgX(X=Cl,Br,I)玻璃为基玻璃,在270℃的环境温度下,以氮气作为保护气氛,成功地进行了K -Ag 离子交换。在50GeS2-25Ga2S3-25AgI玻璃中,K 离子的交换深度可达256μm,并对交换深度、离子扩散系数以及离子浓度之间的规律进行了初步研究。通过离子交换研究,为制备硫卤玻璃光波导奠定了基础,并可以进一步拓宽硫卤玻璃的应用前景。     

Ho~(3+)/Yb~(3+)共掺TeO_2-ZnO-ZnX_2(X=F,Cl,Br)玻璃的结构和红外发光特性(英文)

采用熔融法制备TeO2-ZnO-ZnX2(X=F,Cl,Br)系统氧卤玻璃块体,并测定了玻璃的各项特征温度。通过Raman光谱和X射线光电子能谱分析了卤化物的引入对玻璃网络结构稳定性的影响。结果表明,加入ZnF2比加入ZnCl2或ZnBr2对Ho3+/Yb3+共掺的碲酸盐玻璃的近红外荧光输出有更明显的效果和规律性。与加入ZnCl2和ZnBr2相比,加入ZnF2对Ho3+/Yb3+共掺的碲酸盐玻璃近中红外的荧光输出影响更加明显和规律。ZnF2虽会抑制1μm处发光但能增强1.2和2μm的发光,同时2μm处荧光输出的量子效率也得到大幅提升。比起使用ZnBr2,使用ZnF2和ZnCl2替代ZnO能更好地提高玻璃的光学性能和热稳定性。在这3种卤化锌中,氟化锌对稀土发光的增强起着更为重要的作用。     

层状LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(1.95)Y_(0.05)(Y=O,F,Cl,Br)正极材料的合成及高温电化学性能研究

采用溶胶-凝胶法合成层状LiNi1/3Co1/3Mn1/3O1.95Y0.05(Y=O,F,Cl,Br)正极材料,在850℃空气氛围下煅烧20h得到晶型较好的正极材料。以XRD、SEM和充放电测试等手段对材料的晶体结构、表观形貌和电化学性能进行表征。XRD显示F-和Cl-掺杂材料具有高度有序的二维层状结构;充放电测试表明,掺杂F-和Cl-的材料放电比容量、循环性能和倍率性能均优于未掺杂材料,特别是掺杂F-材料在55℃,电压范围为2.0～4.6V,0.15mA电流下首次放电比容量高达207.5mAh/g,且0.9mA电流下第60次循环的容量仍达到165.1mAh/g。掺杂Br-的材料结构稳定性、循环性能和放电比容量均比未掺杂材料差。     

Systematic study of optoelectronic and transport properties of cesium lead halide (Cs2PbX6; X=Cl,Br, I) double perovskites for solar cell applications

A systematic density functional theory investigation of Cs₂PbX₆ (X = Cl, Br, I) double perovskites is presented. The lattice constants are computed after structure optimization and using Birch-Murnaghan equations, which agree to the experimental literature. The mechanical stability conditions satisfy Born criteria, and the ductile nature is evidenced by the calculated Poisson's (v) and Pugh's ratios (B₀/G) because all three double perovskites exhibit values higher than the respective critical values v = 0.26 and B₀/G = 1.75. A detailed study of the optoelectronic properties reveals these double perovskites as promising candidates for future optical devices due to their direct band gaps (within 0.45–2.54 eV) and large absorption coefficients 5.95 × 10⁵ cm⁻¹, which are suitable for solar cell applications. ZT calculations demonstrate minute variations within 200–800 K and computed parameter values are quite favorable for thermoelectric applications of these materials in the future. A p-type semiconducting nature is predicted by the computed thermoelectric properties. Additionally, computed refractive indices show Cs₂PbBr₆ and Cs₂PbI₆ exhibiting super-luminescent properties in the UV range. Therefore, the studied double perovskites provide further interest for future energy conversion and photonic based technologies.     

Ag/AgX（X=Cl,Br,I）等离子共振光催化剂的研究进展

银/卤化银[Ag/AgX（X=Cl,Br,I）]光催化剂作为一种新型光催化剂,由于在可见光区域具有明显的等离子共振效应从而显示了优异的可见光催化降解有机污染物的活性,引起了人们的极大重视。本文主要对Ag/AgX（X=Cl,Br,I）等离子体光催化剂的结构、光催化降解有机物机理、催化剂制备等进行了综述。Ag/AgX（X=Cl,Br,I）的活性普遍较高,通过半导体复合及形貌尺寸的控制,光催化性能得到进一步改善。进而论述了Ag/AgX体系等离子体共振光催化剂在工业染料废水处理上的应用现状,并对Ag/AgX（X=Cl,Br,I）等离子体光催化剂在高浓度、成分复杂污水体系处理中的应用进行了展望。     

Intrinsic point defects and charge carrier trapping in monolayer BiOX (X = I,Br, and Cl)

Two-dimensional (2D) layered bismuth oxyhalides, BiOX (X = I, Br, and Cl), have great potential in optoelectronics and photocatalysis applications. The intrinsic point defects are crucial for carrier conductivity and transport. However, the understanding for defect physics of 2D atomic-scale BiOX are still unclear. Herein, through the first-principles calculations, we investigate the formation of intrinsic point defects and their effect on charge carrier trapping in 2D monolayer BiOX. Under a O-poor condition, the donor defects, such as the Bi_ad, Bi_X, V_O, and V_X, can form spontaneously and induce a high n-type conductivity. The V_X shows a shallow transition level and has no defect states. In contrast, the Bi_ad, Bi_X, and V_O display deep transition levels and obvious localized defect states that are responsible for the charge carrier trapping. As O becomes richer, the concentration of acceptor defects increases. Nevertheless, the donor and the acceptor defects can strongly compensate each other, pinning the Fermi energy in the band gap. The dominant acceptor defects, such as the Br_Bi, O_Br, and O_Cl, show the deep transition levels and serve as carrier traps due to the charge localized around the defect sites. Our work gives an insight into the defect physics of atomic-scale 2D BiOX and provides a guidance for their optoelectronics and photocatalysis applications.     

Spectral Investigation and Color Properties of Copper(I) Halides CuX (X=F,Cl, Br,I) in Pyrotechnic Combustion Flames

Four pyrotechnic compositions containing copper or its compounds and different halogens were tailored to produce the emitters copper(I) fluoride, CuF, copper(I) chloride, CuCl, copper(I) bromide, CuBr, and copper(I) iodide, CuI. The UV/Vis emission spectra of these compositions were measured and allow for the identification and assignment of the above species CuF, CuCl, CuBr, and CuI. Copper(I) fluoride is a poor emitter with a very narrow green band centered at λ=493 nm only. In contrast all the other copper(I) monohalides have extended band systems with boundaries ranging from about λ=400 to 540 nm. CuCl yields a blue chemiluminescence, whereas CuBr surprisingly gives a highly saturated (Σ=95 %) intense blue violet (λ_d=459 nm) emission. CuI displays an overall bluish green emission only due to more intense band systems λ>500 nm. The spectral properties of all the emitters and the color values of the emitters in the 1931‐CIE color diagram are presented.     

Synthesis, structure, and photovoltaic property of a nanocrystalline 2H perovskite-type novel sensitizer (CH3CH2NH3)PbI3

A new nanocrystalline sensitizer with the chemical formula (CH₃CH₂NH₃)PbI₃ is synthesized by reacting ethylammonium iodide with lead iodide, and its crystal structure and photovoltaic property are investigated. X-ray diffraction analysis confirms orthorhombic crystal phase with a = 8.7419(2) Å, b = 8.14745(10) Å, and c = 30.3096(6) Å, which can be described as 2 H perovskite structure. Ultraviolet photoelectron spectroscopy and UV-visible spectroscopy determine the valence band position at 5.6 eV versus vacuum and the optical bandgap of ca. 2.2 eV. A spin coating of the CH₃CH₂NH₃I and PbI₂ mixed solution on a TiO₂ film yields ca. 1.8-nm-diameter (CH₃CH₂NH₃)PbI₃ dots on the TiO₂ surface. The (CH₃CH₂NH₃)PbI₃-sensitized solar cell with iodide-based redox electrolyte demonstrates the conversion efficiency of 2.4% under AM 1.5 G one sun (100 mW/cm²) illumination.     

Preparation and Crystal Structures of Some Compounds of the A3 BX5 Type (A = Cs,Tl, NH4, B = Mn,Fe, Co,X = Cl,Br)

The compounds Cs₃ FeBr₅, Cs₃MnBr₅,Tl₃FeCl₅, Tl₃CoCl₅, (NH₄)₃FeCl₅ and (NH₄)₃CoCl₅ were prepared and their crystal structures determined. Cs₃FeBr₅, Cs₃MnBr₅, Tl₃FeCl₅ and Tl₃CoCl₅ belong to the tetragonal system, space group 14/mcm, isostructural with Cs₃CoCl₅ [1]. (NH₄)₃FeCl₅ and (NH₄)₃CoCl₅ belong to the orthorhombic system, space group Pnma, isostructural with (NH₄)₃ZnCl₅ [2].     

The metal-chain complexes (X)[Os(CO)3(CNBu)]3Mn(CO)5 (X=Cl, Br, I)

In what is a new metal-chain forming reaction, (X)[Os(CO)₃(CNBu^t)]₃Mn(CO)₅ (X=Cl, Br, I) complexes have been prepared by the successive addition of Os(CO)₄(CNBu^t) to Mn(CO)₅(X) in hexane. The crystal structure of the iodo derivative reveals it to contain an approximately linear Os₃ Mn chain of metal atoms.     

A promising optical limiting material: Tunable third-order nonlinear optical properties of robust CsPbX3 (X=Cl/Br,Br) nanocrystals glasses

As laser technology advances, the importance of laser protection puts an urgent demand for robust and high-efficient optical limiting materials. In this work, CsPbX₃ (X = Cl/Br, Br) NCs were synthesized by precisely controlling the ratio of Cl⁻ to Br⁻ and the heat treatment temperature, and the third-order nonlinear (TONL) optical properties of them were investigated systematically and deeply based on a nonlinear optical imaging technique with the phase-object (NIT-PO) at 532 nm for the first time. All of them demonstrate strong reverse saturation absorption (∼10^-12–10^-11 m/W), and the sign of TONL refraction index (γ) relates to the component (CsPb(Cl/Br)₃ NCs glasses: ∼10^-20 m²/W, CsPbBr₃ NCs glasses: ∼−10^-20 to 10^-19 m²/W). In addition, they have excellent characteristics of thermal stability and water stability, as well as photostability under 455 nm laser irradiation, indicating that it is a promising optical limiting material.     

A general synthesis of titanocene(III) complexes Cp2TiX(PMe3) (X=F,Cl, Br,I, Me,SMe) by comproportionation of Cp2TiX2 and Cp2Ti(PMe3)

The titanocene(III) complexes Cp₂TiX(PMe₃) (X=F, Cl, Br, I, Me, SMe) are readily synthesized by comproportionation reactions of Cp₂Ti(PMe₃)₂ and Cp₂TiX₂. The products are characterized by EPR spectroscopy.     

Structural,optical, electrical and dielectric properties of (Sr1-xMgx)(Sn0.5Ti0.5)O3 (X=0.00, 0.25, 0.50, 0.75) ceramics via solid state route

We have prepared (Sr_1-xMg_x)(Sn_0.5Ti_0.5)O₃, (X = 0.00, 0.25, 0.50, 0.75) samples by the solid state reaction method and studied the structural, optical, electrical modulus and the other dielectric properties of the samples with respect to variation in frequencies (1 × 10⁹ to 2 × 10⁹ Hz) using Impedance Analyzer. This study suggests that the XRD patterns of the samples have shown that this possesses cubic perovskite structure in space group Pm-3m and scanning electron microscope was used to analyze the grain size distribution and porosity of the ceramic. The dielectric properties of these materials were strongly dependent upon on concentration X as well as amount of frequencies. The existence of metal oxygen bonds of Sr–Ti–O was verified by Fourier Transform Infra Red (FTIR) spectrum at 540 cm⁻¹. The highest PL intensity of 716.38 that exhibits the green emission (508.5 nm) was obtained for the composition of (Sr_0.25Mg_0.75)(Sn_0.5Ti_0.5)O₃. AC conductivity slowly decreases with increasing Mg substitution and also the sample (Sr_0.25Mg_0.75)(Sn_0.5Ti_0.5)O₃ having the lowest (constant) value of conductivity at 1 GHz–2GHz.