Improved thermoelectric performance in p-type Bi_(0.48)Sb_(1.52)Te_3 bulk material by adding MnSb_2Se_4

Bismuth telluride(Bi_2Te_3) based alloys, such as p-type Bi_(0.5)Sb_(1.5)Te_3, have been leading candidates for near room temperature thermoelectric applications. In this study, Bi_(0.48)Sb_(1.52)Te_3 bulk materials with MnSb_2Se_4 were prepared using high-energy ball milling and spark plasma sintering(SPS) process. The addition of MnSb_2Se_4 to Bi_(0.48)Sb_(1.52)Te_3 increased the hole concentration while slightly decreasing the Seebeck coefficient, thus optimising the electrical transport properties of the bulk material. In addition, the second phases of MnSb_2Se_4 and Bi_(0.48)Sb_(1.52)Te_3 were observed in the Bi_(0.48)Sb_(1.52)Te_3 matrix. The nanoparticles in the semi-coherent second phase of MnSb_2Se_4 behaved as scattering centres for phonons,yielding a reduction in the lattice thermal conductivity. Substantial enhancement of the figure of merit, ZT, has been achieved for Bi_(0.48)Sb_(1.52)Te_3 by adding an Mn_(0.8)Cu_(0.2)Sb_2Se_4(2mol%) sample, for a wide range of temperatures, with a peak value of 1.43 at 375 K, corresponding to ~40% improvement over its Bi_(0.48)Sb_(1.52)Te_3 counterpart. Such enhancement of the thermoelectric(TE) performance of p-type Bi_2Te_3 based materials is believed to be advantageous for practical applications.     

稀土离子掺杂氟化物激光晶体研究进展

稀土离子掺杂氟化物晶体具有宽透光波段高透过率、低声子能量、长荧光寿命、负热光系数等优良特性,可以产生从紫外到中红外波段激光,是一类重要的激光增益介质。本文综述了本团队在稀土离子掺杂LiLuF₄、LiYF₄、BaY₂F₈、LaF₃、PbF₂、CeF₃等氟化物晶体生长、光学和激光性能等方面的研究进展,总结了稀土离子共掺敏化、退激活、能级耦合调控以及多离子发光等方面的研究工作,展望了稀土离子掺杂氟化物激光晶体的研究发展趋势。     

国产大尺寸钛宝石晶体助力世界最强脉冲激光放大输出

自主研发成功热交换法生长大尺寸钛宝石晶体设备,生长出完整无开裂的钛宝石激光晶体毛坯,经加工获得尺寸达φ235 mm×72 mm的晶体元件.在180 mm口径范围内,晶体光学均匀性达到5.52×10-5,晶体应力双折射为5.0 nm/cm.大尺寸钛宝石晶体应用于上海超强超短激光实验装置,获得339 J激光脉冲能量输出,峰值功率达10.3 PW.     

一道例题的别解与引申

充分发掘空间几何元素(点、线、面)的位置关系,对解决空间直线、平面问题很有帮助.基于此,对一道课本例题给出别解并加以引申.     

函数单调性在证明不等式中的应用

利用函数的某些性质解决不等式的证明问题 ,在高等数学中是经常使用的方法 ,本文结合实例 ,利用函数的单调性来处理不等式的证明问题 .例 1　当 0 f (x) >limx→ π2 - 0f (x) ,而 limx→ 0 f (x) =1 ,limx→ π2 - 0f (x) =2π ,故 1 >sinxx >2π.例 2　当 x>0时 ,证明 :x -x22 相似文献   

中红外氟化物激光晶体的生长和性能优化研究

中红外激光晶体材料作为激光技术核心增益材料之一,在军事光电对抗、激光医疗、卫星遥感、环境监测、基础科学等领域具有非常重要的应用.本文介绍了近年来在中红外氟化物激光晶体材料中,关于晶体生长、光学性能优化以及中红外激光性能等方面的研究工作,特别是在中红外光学性能优化调控方面,主要介绍基于稀土能级耦合的相互作用,有效抑制发光离子的自终止效应,以及为发光离子提供有效泵浦通道.     

符号法判定平面划分空间问题

给出了平面划分空间的符号判定 ,并举例应用