【摘要】 <正> 我国蕴藏着丰富的稀土元素,利用镧代替钇,研究高T_c超导体具有一定的经济意义。但镧和钡的原子半径相近而比钇大得多,这给制备工作带来了困难。国内曾有几个单位制备出了T_c80K的超导相,但都难以重复。日本A.Maeda等人合成了T_c80K的正交LaBa₂Cu₃O_7-δ超导相,测定了晶体结构和相转变温度。最近我们也开展了对这个体系的研究,本文将给出隐定的高T_cLaBa₂Cu₃O_7-δ超导相的制备方法、相变温度、晶体结构以及超导性能与正交性的关系。更多还原

【Abstract】 A stable orthorhombic superconduting phase LaBa₂Cu₃O_7-δ, with T_c 82K and Meissner effect 13.6%, has been prepared by citric acid complexation with nitrates. It is determined to be an orderly three layer Ba-La-Ba, oxygen-deficient perovskite structure by X-ray powder diffraction and atomic valence calculation. Through high temperature XRD and DTA-TG study,the phase transition of orthorhombic into tetragonal structure is found to be reversible, and occurs at 450℃, not the value 350℃ proposed by A.Maeda et al.The superconduting properties are improved as the responsible orthorhombic structure deviates more from tetragonality.更多还原