| Superconductor is a special functional material which is very promising in the superconducting state.The study of superconducting physics has always been a hot spot in condensed matter physics.First of all,with the continuous expansion of the family of superconducting materials and the continuous renewal of the critical temperature of superconductivity,how to further improve the critical temperature of superconductivity(Tc)is still an important work.New superconducting materials with higher critical parameters need to be explored.Secondly,at the current superconducting temperature can be arrived,improving superconducting properties of superconductors such as magnetism and electricity will provide more powerful application performance support for the current superconducting technology application,and it is also an important research topic at present.Finally,although many theoretical results have been used to explain superconductivity,the superconducting mechanism of all kinds of superconductors has not yet reached a consensus.The mechanism and process of superconducting conduction still need to be explored continuously.In this paper,we have mainly carried out two parts:the preparation of iron based superconducting thin film FeSe1-xTex(FST)and copper oxide superconducting thin film YBa2Cu3O7-?(YBCO)by pulsed laser deposition(PLD).(1)for the FST superconducting film,the growth conditions are explored,the properties of the materials are optimized,and the influence of the material and the interface microstructures on the superconductivity is studied.(2)for YBCO superconducting thin films,it can be found that the superconductivity can be improved by the double doping of nanoparticles and nanorods to optimize the flux pinning effect.This paper select FeSei-xTex 11-type high temperature iron-based superconducting thin film as the research object,because this kind of iron based superconductors with chemical composition and crystal structure is relatively simple.It is more easily to find the effects on superconductivity factors through the method of experimental comparison and simulation analysis.The current research on iron-based superconducting materials are mostly concentrated in bulk and monolayer,for FST films of the samples is relatively less.and its special two-dimensional plane makes the thin film samples of rich research value.The preparation of FST superconducting thin films with 60 nm thickness is by pulsed laser deposition(PLD)thin film growth process.to control the superconductivity optimization sample in the experiment in details is based on the growth temperature,the target composition,growth rate and substrate lattice parameter.Through interface design,the microstructure of the film interface is changed,and then the FeSe0.5Te0.5 superconducting thin film with critical temperature Tc= 17 K has been prepared,which has reached the advanced level in the world.Study on FST thin films in strong magnetic field show that,the superconducting films have high critical magnetic field,small anisotropy and high critical current density.This advantages show good application prospect.This paper also attempted to explore the magnetic anisotropy of FST superconducting thin films,and the relationship between substrate selection and lattice structure.It also explained the change of FST lattice constant caused by Ce02 buffer layer,which promoted the FST superconductivity and changed the magnetic anisotropy.It is found that the change in the distance of the"FeSe" layer in FST thin film will greatly help to improve the critical temperature of the iron base superconductor.For the YBCO superconducting films,were studied in this paper by using the method of artificial control to prepare the BaZrO3 nanorods(BZO-NRs)and Y2O3 nanoparticles as,artificial pinning centers(APCs)for magnetic flux,thereby improving the flux pinning properties of doped samples.It is also using pulsed laser deposition(PLD)process by doping the YBCO target with certain amounts of BZO,Y2O3 or other impurities.The nanorods and nanoparticles self-assembly growth in the YBCO superconducting films.And by controlling the parameters,and arranging nano defects,we can design the landscape of the APCs.The results show that the double doping can release the BZO/YBCO surface strain,and can make the APCs in more reasonable arrangement,so as to improve the anisotropic of YBCO thin film and in magnetic field,which improves 140%superconducting critical current,and weaken the anisotropy of the magnetic field up to 32%.Its significance lies in the promotion of high temperature superconductor material in current critical temperature range(generally around 77 K).It is of great help to the application of superconducting tape,such as superconducting cable,superconducting motor,superconducting magnetic field and so on.In addition,through the analysis of simulation model of two-dimensional energy,It is explained the effect of double doping,vicinal substrate surface,doping concentration,and the different doping materials with different lattice constant such as BaSnO3,BaZrO3,BaHf03,Y203 for controlling the APCs landscape in the YBCO film.It provides a reference for further improving the magnetic flux pinning ability of the superconducting thin film. |
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