Dielectric and piezoelectric properties of(110) oriented Pb(Zr_(1-x)Ti_x)O_3 thin films

A phenomenological Landau–Devonshire theory is developed to investigate the ferroelectric, dielectric, and piezoelectric properties of(110) oriented Pb(Zr_(1-x)Ti_x)O_3(x = 0.4, 0.5, 0.6, and 0.7) thin films. At room temperature, the tetragonal a_1 phase, the orthorhombic a_2c phase, the triclinic γ_1 phase, and the triclinic γ_2 phase are stable. The appearance of the negative polarization component P_2 in the a_2c phase and the γ_1 phase is attributed to the nonlinear coupling terms in the thermodynamic potential. The γ phase of the Pb(Zr_(1-x)Ti_x)O_3 thin films has better dielectric and piezoelectric properties than the a_2c phase and the a_1 phase. The largest dielectric and piezoelectric coefficients are obtained in the Pb(Zr_(0.5)Ti_(0.5))O_3 thin film. The piezoelectric coefficient of 110–150 pm/V is obtained in the(110) oriented Pb(Zr_(0.5)Ti_(0.5))O_3 thin film, and the Pb(Zr_(0.3)Ti_(0.7))O_3 thin film has the remnant polarization and relative dielectric constant of 50 μC/cm~2 and 100, respectively,which are in agreement with the experimental measurements reported in the literature.     

GaAs在光通讯波段的超快非线性光学研究

采用Z-扫描和泵浦-探测技术,在光通讯波段对砷化镓(GaAs)单晶进行了非线性动力学以及非线性光学的实验研究.飞秒泵浦-探测实验结果表明,三阶非线性光学效应源于砷化镓单晶对飞秒激光的瞬态双光子吸收,而五阶非线性光学效应源于砷化镓单晶双光子吸收诱导的自由载流子吸收效应.通过Z扫描实验,得到了关于GaAs单晶所有的非线性光学参数,包括双光子吸收系数、三阶非线性折射系数、双光子吸收诱导的自由载流子吸收截面以及双光子吸收诱导的自由载流子折射截面.结果表明,砷化镓单晶在制造光限幅器件和光电探测器方面具有良好的发展前景.     

新疆产业结构趋同及其合理性分析

区域产业结构是否合理与区域经济能否健康发展有着密切联系.区域产业结构趋同是在经济发展过程中区域间产业结构的相似表现.利用2010年至2017年数据,通过计算区位熵和产业结构相似系数对新疆14个地州的产业集聚水平和产业结构趋同化进行测度.结果表明:新疆14个地州一、二、三产产业结构趋同化,随时间呈现产业相似的演变特征,南北疆产业结构差异逐渐减弱.为此提出发挥区域优势、延伸产业链、加强区域合作、提高配置效率的对策建议.     

1995-2017年新疆区域经济差异的时空特征分析

以新疆为研究区域,计算14个地州的变异系数和泰尔指数,利用ESDA方法对82个县市单元进行空间自相关分析,分析1995-2017年新疆区域经济发展时间和空间总体差异水平变化,并识别经济发展空间格局中的热点区域,探讨新疆区域经济差异,最后从区域机制、产业转移、重点领域、开放战略等方面提出策略建议.