Structure and dielectric properties of highly (100)-oriented PST thin films deposited on MgO substrates

High-quality Pb_0.4Sr_0.6TiO₃ (PST) thin films have been epitaxially grown on MgO (100) substrates at various substrate temperatures by the pulsed laser deposition (PLD) technique. Their crystalline phase structures and surface morphology were measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their in-plane orientation was observed by the Phi scans on the (111) plane. Their dielectric properties were measured by a precision impedance analyzer. Results show that the perovskite phase was stable in PST thin film. The crystalline phase formation of the thin film depended on the deposition temperature. The phase formation ability and (100)-orientation of these films were increased with increasing deposition temperature. Both of the high tunabilities and low dielectric loss of the thin films show that the (100)-oriented PST is a potential material that can be used for tunable applications.     

机载小型化星敏感器遮光罩设计

针对机载小型化星敏感器的消杂光系统进行了研究。以点源透射比(PST)为标准,根据机载小型化星敏感器成像系统自身的特性与遮光罩设计原则,在尽量不增加系统长度的前提下,对消杂光结构进行了设计。利用Matlab计算出遮光罩的尺寸,确定挡光环的位置,结合CAD作图软件进行建模,并使用光学软件TracePro对遮光罩的消杂光效果进行了仿真和分析,在太阳规避角30°时的点源透射比达到了5.536×10-10,达到系统要求的性能指标。设计的遮光罩能够成功地抑制杂散光,可以满足机载小型化星敏感器的使用要求。     

1-丙烯-1,3-磺酸内酯对高电压锂离子电池的影响

用循环伏安和交流阻抗谱测试研究1-丙烯-1,3-磺酸内酯(PST)用作电解液添加剂的电化学行为,用X射线能谱对电极表面元素进行分析,考察添加剂PST对4.4 V高电压钴酸锂锂离子电池的影响。PST能在电池电极表面形成固体电解质相界面膜,抑制溶剂分子在负极的共嵌和还原分解,改善锂离子电池的循环性能和高温性能,但使低温性能劣化。     

移相变压器在特高压直流双极闭锁故障中的应用

特高压直流输电系统双极闭锁故障时会导致输电断面上大量功率的瞬间缺失,从而使部分联络线严重过负荷。针对该问题,提出了在特定线路装设移相变压器来将过载联络线的部分潮流转移到其他轻载联络线上,从而减少了直流线路故障时所需切除的负荷量,提高了电网的供电可靠性。通过讨论移相器的数量和选址问题,总结出了不同情况下的决策方法,并以一个总负荷约为22 000 MW的大系统为例,确定了移相器的类型和具体模型,并推导和计算了移相器的相关参数,利用PSASP平台仿真出了不同移相角时各联络线的潮流。研究结果表明,移相器能够实现联络线之间输送功率的转移,充分利用了输电断面上联络线的输电能力,从而能够改善特高压直流闭锁故障带来的输电断面联络线过载问题。     

Ti－48at％合金PST晶体的生长与显微组织的研究

采用磁悬浮区域熔炼的方法制取Ｔｉ－４８ａｔ％Ａｌ合金的ＰＳＴ晶体。并对其显微组织进行了金相及ＴＥＭ的观察与分析。结果表明，ＰＳＴ晶体的生长取决于生长速率。当生长速率小于５ｍｍ／ｈ时可获得ＰＳＴ晶体，而当生长速率增至１００ｍｍ／ｈ时，得到柱状晶晶体。ＴＥＭ观察的结果表明，在ＰＳＴ晶体的片层组织中存在三种类型的ＴｉＡｌ／ＴｉＡｌ有序畴界，即真孪晶型，伪孪晶型，１２０°旋转孪晶型界面。     

Transmission electron microscopy of lead scandium tantalate thin-films

Preliminary results are reported on the examination of lead scandium tantalate (PST) ferroelectric thin-films by transmission electron microscopy (TEM). The samples were grown on sapphire substrates by the solution-gel route and were examined in both plan and transverse section. Scanning electron micrographs of the surface of the samples of PST on sapphire showed that the PST films were invariably cracked. TEM examination of the PST on sapphire in plan section revealed that two distinct distributions of PST grains had grown on the sapphire (100 and 1500 nm diameter) and that nucleation of PST on the sapphire surface was associated with surface flaws and dislocations. TEM samples prepared in transverse section revealed that ordering of the Sc and Ta cations was greater at the PST-sapphire interface than within the interior of the thin-film. Small crystallites of an unidentified second phase were also observed to have formed in the centres of PST grains.     

Correlation between dielectric properties and strain in Pb0.5 Sr0.5TiO3 thin films prepared by using the sol–gel method

Pb_0.5Sr_0.5TiO₃ (PST) thin films were fabricated by the alkoxide-based sol–gel process using spin-coating method on Pt/Ti/SiO₂/Si substrate. The PST films annealed from 500 °C to 650 °C for 1 h show a perovskite phase and dense microstructure with a smooth surface. The grain size and dielectric constant of PST films increase with the increase in annealing temperature, which reduces the SiO₂ equivalent thickness of the PST film. The crystallinity or internal strain in the PST thin films analyzed from the diffraction-peak widths correlates well with the decrease in the dielectric losses. The dielectric constants and dielectric loss (%) of the PST films annealed at 650 °C (t_eq=0.89 nm) were 549 and 0.21%, respectively.     

掺钐钛酸铅铁电薄膜的制备和主要性质

采用金属有机分解法(MOD)在P型Si(111)衬底上制备了Pb0.85Sm0.1TiO3(PST)薄膜。用X-射线衍射技术研究了退火温度对薄膜的结构和结晶性的影响。同时还研究了薄膜的介电、铁电和绝缘性能。结果发现在600°C下退火1h的PST薄膜呈钙钛矿结构;在0～16V范围内,薄膜的漏电流小于1.17×10-7A;在±10V的偏压范围内,电容-电压(C-V)记忆窗口宽度为4.5V;在室温10kHz下,其介电常数为37.25,介电损耗为0.042。     

Fracture in lamellar TiAl simulated with the cohesive model

Fracture behaviour of lamellar TiAl is studied by means of experiments and numerical simulations using a cohesive model. The fracture process can be described by two cohesive parameters: traction, T₀, and separation work, Γ₀. These are identified for polysynthetically twinned crystals (PST) and a polycrystalline TiAl alloy by comparison of the numerical simulations with experimental fracture tests. The appropriate shape of the traction-separation law for quasi-brittle fracture was identified. The simulation of the PST crystal deformation is based on crystal plasticity including the specific lamellar orientation relations. In a PST crystal, fracture occurs by inter- and translamellar fracture. In an extruded polycrystal, the lamellae of the colonies are randomly aligned in radial direction but more uniformly in extrusion direction for which different fracture toughness values are obtained. For the polycrystalline γTiAl conventional J₂ plasticity is applied, which seems appropriate to predict macroscopic effects either for stable crack extension or unstable failure. The cohesive separation, δ₀, can be interpreted as a characteristic length for a representative microstructural volume.     

星载大气主要温室气体监测仪杂光模拟分析

杂散光分析是提高信噪比,保证测量精度的关键手段之一。依据星载大气主要温室气体监测仪光学系统结构及其工作特点,设计了仪器的外遮光罩和前置望远系统的遮光筒。建立仪器的三维实体模型,利用Tracepro软件对仪器氧气通道(758~768 nm)的杂散光进行了分析,给出系统杂散光点源透射比(PST,Point Source Transmittance)曲线, PST在30离轴角小于510-7。依据PST拟合曲线,通过积分计算得到杂散光系数小于4%。结果表明:杂散光抑制措施效果明显,杂散光水平达到了设计指标要求。