YBCO高温超导体与氧化物衬底的化学反应性

THE CHEMICAL INTERACTION OF YBCO HIGH-Tc SUPERCONDUCTOR WITH OXIDE SUBSTRATE MATERIALS

在高温超导膜的制备过程中,膜与衬底的化学反应能导致超导体的化学组成,晶体结构和输运性质发生改变,因而是影响膜质量的重要因素。这种化学反应与衬底材料的性质密切相关。但是,至今尚缺乏一种比较令人满意的、普遍适用的超导体与衬底相互作用理论和用于估计这种反应性的参数。本文首次提出YBa_2Cu_3O_7(YBCO)高温超导体与氧化物衬底的化学反应本质上是固态酸碱反应,其反应性可用衬底氧化物的酸碱参数来估计,主要反应产物为含鋇的衬底氧化物盐类。本文提出的这一规律也与实验结果符合。

Chemical experiments and XPS analysis indicate that YBCO superconductor is a relatively strong base, and Ba-O components in YBCO is primarily responsible for its hasicity. Based on the basic property of YBCO, it is suggested that the chemical interactions between YBCO and oxide substrate materials is primarily solid acid-base reactions. The acid-base parameters for substrate materials (MgO, ZrO_2, Al_2O_3 and SiO_2) are calculated and used as a scale for measuring the acidity or basicity of the oxide substrates and for evaluating the YBCO-substrates chemical reactivity. It is found that the chemical reactivity increases with increasing acid-base parameter (or increases with increasing acidity) of the substrate materials. Therefore the chemical reactivity with YBCO increases in the order of MgO<ZrO_2<Al_2O_3<SiO_2. The above rule is also suitable for chemical reaction of BSCCO superconductor with oxide substrate materials.