Luminescence properties of Sn2P2Se6 crystals

A large family of Sn_2yPb_2(1−y)P₂S_6xSe_6(1−x) semiconductor-ferroelectric crystals were obtained by the Bridgman technique. The photoluminescence properties of the Sn_2yPb_2(1−y)P₂S_6xSe_6(1−x) family crystals strongly depend on their chemical composition, excitation energy and temperature. The influence of the Pb → Sn and S → Se isovalent substitutions on the luminescence properties of a crystal with the Sn₂P₂Se₆ basic composition was investigated. A broad emission band observed in the Sn₂P₂Se₆ crystal with a maximum roughly at 600 nm (at T = 8.6 K) was assigned to a band-to-band electron-hole recombination, whereas broad emission bands, peaked near 785 nm (at T = 8.6 K) and 1025 nm (at T = 44 K) were assigned to an electron-hole recombination from defect levels localised within the bandgap. Possible types of recombination defect centres and specific mechanisms of luminescence in the Sn₂P₂Se₆ semiconductor-ferroelectric crystals were considered and discussed on the basis of the obtained results and the referenced data.     

Highly efficient acousto-optic diffraction in Sn2P2S6 crystals

We have studied the acousto-optic (AO) diffraction in Sn2P2S6 crystals and found that they manifest high values of an AO figure of merit. The above crystals may therefore be used as highly efficient materials in different AO applications.     

In掺杂对CdMnTe晶体性能的影响

采用垂直Bridgman法生长了In掺杂Cd0.3Mn0.2Te晶体（CdMnTe：In）和本征的Cd0.8Mn0.2Te晶体（CdMnTe）。X射线粉末衍射、X射线双晶摇摆曲线和位错密度测试表明，所生长晶体均为立方闪锌矿结构，半峰宽为40～80arc Sec，位错密度为100～100cm^-2，结晶质量良好．In掺杂不影响晶体的结构和结晶质量。电流．电压（I-V）测试表明，CdMnTe：In晶体的电阻率为1～3×10^9Ω·cm，与CdMnTe晶体相比上升了3个数量级．近红外光透过光谱（IR transmission）研究发现In掺杂后CdMnTe晶体红外透过率降低，在波数范围4000～1000cm^-1，CdMnTe晶体红外透过率为51．2％～56．4％，而CdMnTe：In的红外透光率为15．4％～6％。     

Effect of Sn doping on the growth and optical properties of AgI nanoparticles

Controlled iodization and Sn doping of vacuum-evaporated Ag films has helped understand the initial-stage kinetics of AgI nanoparticle growth under ambient conditions. Use of XRD, optical spectroscopy, and AFM has unravelled systematic correlation between Sn-induced disorder in Ag crystal structure, nanoparticle size, and exciton growth dynamics. Sn doping of Ag leads to three specific effects: removal of UV absorption minimum in Ag, introduction of a plasmon-type absorption in the red region, and a reduction in particle size in thicker (than 10 nm) films (but an increase in particle size in 10 nm films) relative to that in undoped Ag films.     

Pseudocapacitive Sodium Storage by Ferroelectric Sn2P2S6 with Layered Nanostructure

Sodium ion batteries (SIB) are considered promising alternative candidates for lithium ion batteries (LIB) because of the wide availability and low cost of sodium, therefore the development of alternative sodium storage materials with comparable performance to LIB is urgently desired. The sodium ions with larger sizes resist intercalation or alloying because of slow reaction kinetics. Most pseudocapacitive sodium storage materials are based on subtle nanomaterial engineering, which is difficult for large‐scale production. Here, ferroelectric Sn₂P₂S₆ with layered nanostructure is developed as sodium ion storage material. The ferroelectricity‐enhanced pseudocapacitance of sodium ion in the interlayer spacing makes the electrochemical reaction easier and faster, endowing the Sn₂P₂S₆ electrode with excellent rate capability and cycle stability. Furthermore, the facile solid state reaction synthesis and common electrode fabrication make the Sn₂P₂S₆ that becomes a promising anode material of SIB.     

Growth and some properties of Zn5In2S8 single crystal

Zn₅In₂S₈ has been synthesized in the form of single hexagonal platelets. This compound is the fifth member of the layered semiconductor family Zn_xIn₂S_3+x. Optical measurements are used for the evaluation of the energy gap at room temperature. This was found equal to 2.84 eV. The presence of extended composition faults was indicated by the a²-hv diagrams and proved by electron microscopy techniques. Some electrical properties have been studied and an electron trap at E_x=E_c−0.4 eV, with a concentration of about 10¹² cm⁻³ was found to exist. An anisotropy of about 10⁶ was measured in the two directions: Parallel to the layers and vertically to them.     

Morphology and orientation evolution of Cu6Sn5 grains on (001)Cu and (011)Cu single crystal substrates under temperature gradient

The morphology and orientation evolution of Cu6Sn5 grains formed on (001)Cu and (011)Cu single crystal substrates under temperature gradient (TG) were investigated.The initial orientated prism-type Cu6Sn5 grains transformed to non-orintated scallop-type after isothermal reflow.However,the Cu6Sn5 grains with strong texture were revealed on cold end single crystal Cu substrates by imposing TG.The Cu6Sn5 grains on (001)Cu grew along their c-axis parallel to the substrate and finally merged into one grain to form a fully IMC joint,while those on (011)Cu presented a strong texture and merged into a few dominant Cu6Sn5 grains showing about 30° angle with the substrate.The merging between neighboring Cu6Sn5 grain pair was attributed to the rapid grain growth and grain boundary migration.Accordingly,a model was put forward to describe the merging process.The different morphology and orientation evolutions of the Cu6Sn5 grains on single crystal and polycrystal Cu substrates were revealed based on crystallographic relationship and Cu flux.The method for controlling the morphology and orientation of Cu6Sns grains is really benefitial to solve the reliability problems caused by anisotropy in 3D packaging.     

Face shear piezoelectric properties of relaxor-PbTiO(3) single crystals

Poling relaxor-PbTiO(3) single crystals along pseudocubic [011] results in a macroscopic symmetry of mm2, enabling a large face shear d(36) in Zt±45° cut crystals. In order to allow the determination of electrical properties by the resonance method, square samples are required. Using Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1∕3)Nb(2∕3))O(3)-PbTiO(3) crystals, piezoelectric d(36) coefficients were determined to be in the range of 2000-2500 pC∕N, with electromechanical coupling factor k(36)～0.80-0.83. Mechanical quality factor Q～180 and ultralow frequency constant of ～500 Hz m were obtained. Together with the wide temperature usage range (up to ～110 °C) and high ac driving field stability (～5 kV∕cm), such face shear crystals have a promising potential for ultralow-frequency-transducer applications.     

Reflection of light by domain walls in the uniaxial ferroelectric Sn2P2S6

The occurrence of light scattering during light transmission is described for some orientations of an incident laser beam in polydomain crystals of the uniaxial ferroelectric tin thiohypodiphosphate. This scattering is probably caused by the presence of a reflecting layer near the 180° domain walls. A reflecting layer may be formed as a result of the appearance of charged nonparallel domain walls. Pis’ma Zh. Tekh. Fiz. 23, 45–50 (August 26, 1997)     

长期时效对DD6单晶高温合金组织和力学性能的影响

采用螺旋选晶法制备DD6合金单晶试棒,标准热处理后在980℃长期时效2000 h,研究980℃长期时效对DD6单晶高温合金的组织演化及力学性能的影响.结果表明:随着长期时效时间的延长,合金中γ'相的尺寸增大,2000 h后γ'相尺寸约为1μm,没有TCP相析出,合金具有较好的组织稳定性.2000 h长期时效试样在980℃/243 MPa下持久寿命为180.16 h,为热处理态的56.3％;在1070℃/130 MPa下持久寿命为144.42 h,为热处理态的35.31％,断裂模式均为微孔聚集型断裂;相比热处理态的合金,2000 h长期时效态试样760℃的抗拉强度和屈服强度分别降低5.55％和5.88％;980℃的抗拉强度和屈服强度分别下降11％和10.59％.     

再结晶对DD6单晶高温合金轴向高周疲劳性能的影响

为了研究再结晶对二代单晶高温合金DD6高周疲劳性能的影响,对标准热处理的DD6合金进行表面吹砂处理,然后分别在1120℃和1315℃保温4h,以获得不同类型的再结晶组织。在疲劳试验机上分别测试了光滑和含再结晶的DD6合金试样在1070℃的轴向高周疲劳寿命。采用SEM观察DD6合金再结晶组织及疲劳断口。结果表明:胞状再结晶和等轴再结晶降低了DD6合金的轴向高周疲劳性能,胞状再结晶作用小于等轴再结晶;含再结晶的DD6合金试样的轴向高周疲劳断裂机制为类解理断裂和枝晶间的局部韧窝断裂共存的混合断裂;再结晶使DD6合金试样变为多源疲劳断裂。高温条件下,再结晶晶界的存在加快合金试样的氧化损伤,显著缩短早期疲劳裂纹的萌生和扩展时间,降低合金的轴向高周疲劳性能。     

Effect of rare-earth doping on the electrical properties of InSe single crystals

The effect of rare-earth doping (R = Gd, Dy, Ho) to different levels (0, 10^?5, 10^?4, 10^?3, 10^?2, and 10^?1 at %) on threshold switching and low-frequency current oscillations in single crystals of indium selenide, a layered III–VI semiconductor, has been studied in broad ranges of temperatures (77–400 K), wavelengths (0.30–3.50 μm), and illuminances (up to ～10² lx). The results are interpreted in terms of the anisotropic chemical bonding in n-InSe and its response to rare-earth doping.     

锗掺杂二氧化钛薄膜的溶胶凝胶法制备和性能研究

二氧化钛是一种无毒、廉价、稳定的半导体材料,被广泛用作光电化学太阳能电池的电极材料,适当掺杂可以增强其光电性能.以钛酸丁酯和四正丁氧基锗烷为主要原料,采用溶胶-凝胶提拉涂膜法制备了Ge掺杂的TiO_2薄膜.通过X射线衍射、扫描电镜、紫外-可见吸收光谱、电流-电压曲线等测试手段研究了薄膜的结晶性能、微观结构和光电性能随Ge掺杂量的变化规律.结果表明,Ge掺杂量x=0.10时,形成Ti_(1-x)Ge_xO_2固溶体,x=0.15时,形成非晶态.掺锗后薄膜表面颗粒密度增大,薄膜比较致密.随着Ge掺杂量的增加,吸收光谱吸收边蓝移,光电化学性能也得到一定提高.在Ge掺杂量为0.05时,光电流达到最大值17A/m~2.同时,研究了锗掺杂对光电流的影响.     

Low power CW optical limiting properties of bis(2-aminopyridinium)-succinate-succinic acid (2APS) single crystal

The increase in the usage of low power CW lasers in various applications needs for the design of optical limiters with low thresholds. The optical limiting properties and nonlinear refractive index (n₂ = −2.4189 × 10⁻⁸ cm²/W) of transparent organic crystal bis(2-aminopyridinium)-succinate-succinic acid (2APS) single crystal using continuous wave He-Ne laser excitation following Z-scan method have been evaluated. The sample exhibited negative (defocusing) nonlinearity. This thermally induced defocusing nature of 2APS crystal can be used to design the low power optical limiters. As the origin for this nonlinearity is thermal, a complete thermal transport properties such as thermal diffusivity (α_s = 5.97 ± 0.03 × 10⁻³ cm²/s), thermal effusivity (e_s = 1.94 ± 0.02 × 10⁻² J/cm²-K-s^1/2), thermal conductivity (k_s = (4. 66 ± 0.04) × 10⁻³ W/cm-K)) and specific heat capacity (C_ps = (5.61 ± 0.05) × 10⁻¹ J/g-K) of the material were studied following the photopyro electric (PPE) technique.     

Effect of electrical conductivity on poling and the dielectric, pyroelectric and piezoelectric properties of ferroelectric 0-3 composites

We have investigated the effects of electrical conductivity of the constituents on the poling behavior, dielectric, pyroelectric and piezoelectric properties of ferroelectric 0-3 composites. Modeling of polarization behavior is explored for both dc and ac poling procedures. Simulated results show that, in addition to the poling schedule, conductivity plays an important role in the poling process. Calculations are carried out for the time dependent internal electric fields induced by an ac field in dielectric measurements, by modulated temperature in pyroelectric measurement or by stress in piezoelectric measurement. Our previously developed models for dielectricity, pyroelectricity and piezoelectricity have been extended to include the additional contribution from the electrical conductivities. These can be significant for ceramic/polymer composites possessing high conductivity in the matrix phase. Calculated values based on the new model are discussed and compared with the previous models, and in particular the pyroelectric activities reported in the literature for a graphite doped lead zirconate titanate/polyurethane composite. Explicit expressions for the transient and steady state responses are given and the effective permittivity, pyroelectric and piezoelectric coefficients are derived in this paper. Remarkable enhancement in these coefficients is obtained when higher conductivity is introduced in the matrix phase.