热处理工艺对无氟PA-MOD法制备YBCO超导薄膜的影响

Influence of Heat Treatment on YBCO Superconducting Films Prepared by a Fluorine-Free PA-MOD Method

摘要:

采用无氟的高分子辅助金属有机物沉积（PA-MOD）法在（00l）LaAlO3单晶基底上制备了超导转变温度Tc = 90 K的YBCO超导薄膜。研究了高温热处理过程中不同成相温度和气氛湿度对制备高性能YBCO薄膜的影响。通过X射线衍射（XRD）θ-2θ扫描、ω扫描和φ扫描分析了不同热处理工艺制备的YBCO薄膜的双轴织构程度；通过扫描电镜（SEM）测试研究了不同薄膜样品的表面形貌；采用超导量子干涉仪测量了薄膜的超导转变温度曲线和磁化曲线。结果表明，770 ℃干燥气氛中成相的样品具有优异的双轴织构及平整、致密的表面形貌。采用该优化工艺制备的YBCO薄膜在77 K零场下的临界电流密度（Jc）达到2 MA/cm2，是其它工艺制备薄膜Jc的1.7~6.7倍。

Abstract:

YBCO superconducting films with Tc of 90 K were prepared via fluorine-free polymer-assisted metal organic deposition (PA-MOD) on (001) LaAlO3 single crystal substrate. The influence of different firing temperatures and gas humidities during high-temperature heat treatment was investigated to fabricate high performance YBCO films. The degree of biaxial texture for the films by different heat treatments was analyzed by X-ray diffraction θ-2θ scan, ω scan and φ scan. Surface morphologies were studied by scanning electron microscopy (SEM). Magnetic moment versus temperature curves and magnetic hysteresis loops were measured by Quantum-Design SQUID XL (7 T). The results show that the YBCO film fired at 770 oC in dry gas has excellent biaxial texture as well as smooth and dense surface morphology. The YBCO film prepared by this optimized treatment has critical current density Jc of 2 MA/cm2 (77 K, self-field) which is 1.7 to 6.7 times of that for YBCO films by other heat treatments.