Preparation Of (Bi,Pb)-2223 High Temperature Superconducting Thin Films With High Purity

The critical transition temperature of Bi-2223 superconducting thin films can reach up to 110 K,and it exhibits high stability in the air,thus having broad application prospects in the field of modern electronic technology.However,the phase formation temperature range of the Bi-2223 phase is narrow,which leads to the instability of its phase structure at high temperature,so it is difficult to obtain high purity phase.At present,there are many problems in the content of impurity phase and long preparation period of Bi-2223 thin film,which restricts the application of Bi-2223 thin film.This paper mainly discusses the existing problems in the preparation of Bi2223 thin films and explores a process that can obtain a higher phase content,good superconducting performance,and a shorter film-forming cycle.In this study,in order to improve the phase purity of(Bi,Pb)-2223 films,the doping characteristics and heat treatment process of Cu doped Li were studied.The doped(Bi,Pb)-2223 sol with good stability and film forming ability was prepared with metal acetate as raw material,anhydrous methanol as solvent and acrylic acid as additive.Li doped(Bi,Pb)-2223 films were prepared on MgO substrate by sol-gel method.The optimal preparation process parameters were shown as follow:the optimal doping molar ratio of Li element is Cu:Li=2.94:0.08,the optimal heat treatment temperature is 850℃,the optimal heat treatment atmosphere is 4%O2(N2:O2=0.96:0.04),and the optimal heat treatment time is 240 min.Under these conditions,the films were prepared with good c-axis orientation and compact and smooth surface,which the volume fraction of(Bi,Pb)-2223 phase is 85.9%,and Tc=97 K,ΔTc=-12.8 K.In order to further increase the(Bi,Pb)-2223 film phase content,Sb doped(Bi,Pb)-2223 superconducting thin films(Bi cite doped with Sb)were prepared.The optimal doping molar ratio of Sb element is Bi:Sb=1.80:0.10.The effects of heat treatment temperature,heat treatment time and atmosphere on phase purity,superconductivity,growth orientation and surface morphology of the films were investigated.The conclusion is as follows:the(Bi,Pb)-2223 films were prepared with 90.6%phase content when the heat treatment temperature is 865℃,the heat treatment time is 240 min,heat treatment atmosphere is 4%O2(N2:O2=0.96:0.04).And the films have good biaxial texture,which Tc=102 K,ΔTc=18 K.The heat treatment time of the rapid heat treatment method used in this experiment is 5.8h,which is about 60%shorter than that reported in the literature.