VB族元素掺杂对YBa_2Cu_3O_(7-y)电子结构的影响

EFFECT OF DOPED V B ELEMENTS ON ELECTRONIC STRUCTURE OF YBa_2Cu_3O_(7-y)

合成了YBa_2Cu_(3-x)M_xO_(7-y)(M=V,Nb,Ta;x-0.0～0.7)高温超导体。X-射线粉末衍射分析表明,x≤0.6时,体系仍然是正交结构,没有发生正交到四方的相变。体系的晶胞参数随x的不同而异。体系的电阻率和Hall系数随x的增加而逐渐增加,它们的载流子浓度和载流子迁移率却随x的增加而下降。这说明VB族元素的置換影响了YBa_2Cu_3O_(7-y)的电子结构。用晶体场理论对体系的电子结构作了解释。

Superconductors of type YBa_2Cu_(3-x)M_xO_(7-y)(M_y=V,Nb,Ta;x=0. 0～0. 7) have been prepared. No phase-transition from orthorhombie to tetragonal for x≤0. 6 were found by X-ray diffractometry. The lattice parameters of the system vary with the number of x. The D.C. resistivities and the values of Hall effect measured at room temperature showed a progressive increase, but the concentration and the mobility of the carrier decreased gradually with the increase of x. This reveals that the partial substitution by the element of the V B group affects the electronic structure of the superconductor. The change of the electronic structure has been discussed in terms of the crystal field theory.