普朗克常量h的物理学意义

普朗克常量h是能量量子化概念的基石, 更是理解量子力学诸多内容的关键, 本文从4个方面介绍了普 朗克常量的意义和应用, 包括其在量子力学两种形式中的基础作用、 对量子化概念发展的帮助、 改变对物质世界连 续性认识的启发以及质量新标准建立中的作用     

Effects of(La,Sr) co-doping on electrical conduction and magnetic properties of BiFeO_3 nanoparticles

Multiferroic material as a photovoltaic material has gained considerable attention in recent years.Nanoparticles(NPs)La_(0.1)Bi_(0.9-x)Sr_xFeO_y(LBSF,x = 0,0.2,0.4) with dopant Sr~(2+)ions were synthesized by the sol–gel method.A systematic change in the crystal structure from rhombohedral to tetragonal upon increasing Sr doping was observed.There is an obvious change in the particle size from 180 nm to 50 nm with increasing Sr substitution into LBFO.It was found that Sr doping effectively narrows the band gap from～2.08 e V to～1.94 e V,while it leads to an apparent enhancement in the electrical conductivity of LBSF NPs,making a transition from insulator to semiconductor.This suggests an effective way to modulate the conductivity of BiFeO_(3-)based multiferroic materials with pure phase by co-doping with La and Sr at the A sites of BiFeO_3.