在Ag基体上用MOCVD法连续制备YBCO超导带

CONTINUOUS PREPARATION OF YBCO SUPERCONDUCTING TAPE ON Ag SUBSTRATE BY MOCVD

用ＭＯＣＶＤ法在Ａｇ基体上以～１５ｃｍ／ｈ的带速连续制备ＹＢＣＯ超导带．在８００—８５０℃之间沉积的样品均呈强烈ｃ－轴取向；而在７５０－８００℃间，ｃ－轴取向明显减弱．前者为不规则排列的大片状晶结构，而后者为不规则排列的小棒状晶和发育不良的片状晶，或者为小粒状晶堆集．所制样品的Ｊｃ（７８Ｋ，０Ｔ）一般在０．５—１×１０４Ａ／ｃｍ２之间，最好的达到１．４×１０４Ａ／ｃｍ２．

A new hot-wall quartz MOCVD reacter has been developed, which overcomes the drawback of foregoing decomposition of metalorganic source gases and suits for continuous preparation of YBCO superconducting tape on metal substrate. Experiments on preparation of YBCO / Ag superconducting tape has been carried out in this reacter. The experimental results indicate the facts as following: 1. the statically deposited sample consists of homogenous microstructure with a high degree of c-axis orientation and few impurity phases although the average cationic ratio of y: Ba: Cu (l: 2.4 : 3.6)deviates from 1: 2 : 3 evidently. The surface microstructure of this sample is made up of uniformly distributing granular grains. 2. For the dynamically deposited sample. the major phase is YBCO123 phase with a high degree of c- axis orientation, and the surface microstructure consists of large flaky grains (10-20μ m) with some small granular grains between them when the deposition temperature is above 800℃; the impurity phases such as Ba2CuO3, BaCuO2 and CuO arise when sample contains more Ba and Cu while the impurity phases such as 211 and CuO when sample contains more Y and Cu. When the deposition temperature is below 800℃, the c-axis orientation of YBCO layer becomes weak and the impurity phases increase obviously, and the surface microstructure consists of some small granular grains and a large number of oxide particles. 3. The dynamically deposited samples usually have Jc values from 0.5×104A / cm2 to 1 .0×104A / cm2(78K, 0T),and the best one with 0.68μm thickness has a Ic value of 140mA and a Jc value of 1.4×104A / cm2 (78K,0T).