Preparation Of The YBCO-BST Heterostructure By Sol-gel Method

YBa2Cu3O7-? high Tc superconducting thin film exhibit a splendid performance in both critical current density and surface microwave resistance.Since similar crystal structure with BaxSr1-xTiO3(BST)and other perovskite structure ferroelectric materials,the composed of a multilayer heterostructure derived the more efficient turnable microwave devices than conventional devices.In this paper,we present a study of using Sol-gel technique fabricating good quality and performance YBCO and BST thin films on LaAlO3(LAO)substrate,and prepare BST/YBCO multilayer and take dielectric properties tests.The main conclusions are as follows.(1)YBCO and BST simple layers fabricating by various heating processing have been analyzed by SEM,XRD testing methods.The results shows that BST thin films commence crystallization at 600 ? and crystallized at 700?-800?;while YBCO films commence crystallization at 760? and crystallized at 780?-850?.(2)Based on the previous research,BST/YBCO bilayer films on LaAl03(LAO)substrate have been produced.YBCO and BST thin films respectively fabricated at 850? and 750?.The(005)rocking curve measurements and(220)phi scans of YBCO films reveal that the FWHM are 1.99° and 2.78° respectively;the FWHM of(200)? scans and(211)? scans are 3.82° and 4.53° for BST films respectively.The multi-layers present an obvious epitaxial character and superconducting transition temperature of YBCO films is 88K.(3)BST thin films have been fabricated on Pt,LNO and YBCO bottom electrode respectively.The dielectric constant on different bottom electrode are 205.2,205 0,158 3:tunability are 28.3%,22.8%,72.4%respectively at 300K.The dielectric constant and tunnability increased while the dielectric loss reduced with temperature felling.The dielectric constant on different bottom electrode are 266.4,275.2,280.5;tunability are 42.9%,44.7%,83.1%respectively at 80K.BST films on YBCO bottom electrode has the maximum tunnability.