利用熔盐法制备了Ba0.6-y La y K0.4Bi O3和Ba0.6-z Pr z K0.4Bi O32个系列的样品,其中La和Pr的掺杂量y和z分别为0,0.025,0.05,0.1,0.2,0.3,0.4。X射线粉末衍射结果显示,Pr掺杂使得BKBO晶体结构由最初的立方晶系转变成为正交晶系,但是La掺杂样品却没有发生此种晶体结构的变化。La掺杂样品Ba0.6-y La y K0.4Bi O3的准晶格参数a p随掺杂量的增大而线性减小,其变化遵循a p=4.28257–0.02469y(0.025≤y≤0.4)的规律。样品磁性测量结果表明,掺杂样品的超导转变温度T c均随着掺杂量的增大而系统性地减小,并且当掺杂量达到0.2时,2个系统中的超导转变均消失。认为掺杂引起的晶体结构扭曲及铋化合价的不均衡导致了BKBO掺杂系统超导电性的变化。
Two compositional series based on Ba0.6-y La y K0.4Bi O3 and Ba0.6-z Pr z K0.4Bi O3, with y and z being 0, 0.025, 0.05, 0.1, 0.2, 0.3, 0.4, were synthesized using a molten salt method. X-ray powder diffraction data reveal that the initially undoped cubic crystal symmetry expands slightly to orthorhombic with Pr substitution but not with La substitution. A linearly reduction of the pseudo-lattice parameter following a p=4.28257–0.02469y(0.025≤y≤0.4) can be observed in Ba0.6-y La y K0.4Bi O3. A systematic decrease of the transition temperature, T c, is clarified by magnetic measurements and the superconductivity is finally vanished at y, z = 0.2 owing to the distortion of the crystal structure and the disproportionations of bismuth valence.