Study On The Growth Of Air-processed SmBCO Crystals With High Superconducting Performance

Among numerous amount of functional oxides,?RE?_1+xBa_2-xCu₃O_y?RE123,REBCO,RE=Y,Sm,Nd,etc.?superconductors exhibit remarkable superconducting performance of high critical transition temperature?T_c?,high critical current density?J_c?and high trapped field?B?,which have great potential applications in advanced devices,such as flying wheel,motors and maglev transportation.YBCO superconductors have been easily fabricated with large size and high quality.Compared to YBCO systerm,LREBCO?LRE=Sm,Nd,etc.?systerms are more preferable for their more excellent superconductivity,like higher T_c and J_c.However,it is difficult to prepare LREBCO superconductors with high performance for serious substitution of LRE elements on Ba site,especially in air.In order to prepare LREBCO superconductors with desirable cation stoichiometry and excellent physical properties,many studies have been performed to suppress the substitution of LRE/Ba.The oxygen-controlled melt-growth?OCMG?method has been proved to be a reliable approach to obtaining superconductors with nearly ideal stoichiometry,which requires a low pO2?oxygen partial pressure?atmosphere during growth process.As a cost-saving and convenient method,composition-controlled melt-growth?CCMG?featuring the exploitation of Ba-rich precursors is also an effective way to suppress the substitution of LRE/Ba.However,the improvement for superconducting performance of for NdBCO systerm is not as effective as SmBCO systerm.In general,it is of great significance to prepare LREBCO with excellent superconducting properties in a convenient and effective way.In this work,SmBCO bulks with high superconducting performance are successfully grown in an air atmosphere by cooling-rate-control melt-growth?CRCMG?.The main results are displayed below:1?A novel approach to preparing SmBCO bulks with high T_c values by using Normal?Sm123+Sm211?composition in airBy tuning oxygen vacancy,using Normal starting materials,a new method is applied to prepare high T_c Sm123 samples under an air atmosphere in the view of growth kinetics.Firstly,a series of Sm123 multi-grains by spontaneous nucleation and growth were prepared under various cooling rates in air.Optimal cation stoichiometry Sm_1+xBa_2-xCu₃O_y samples with high T_c were obtained under the optimal cooling rate?0.8K/h?.Following this result,the large Sm123 single-domain grain with remarkable superconducting properties?high T_c value and sharp transition?was also gained under the optimized growth procedure by TSMG,which is comparable to ones grown by OCMG and CCMG.2?Research on superconducting property of SmBCO by CRCMG and CCMG.Firstly,the combined effect of CRCMG and CCMG on superconting properties of SmBCO multi-grains is studied,which shows a lower optimal cooling rate?0.5K/h?.Then,by using Ba-rich precursor?Sm242?,the trapped filed of SmBCO bulks is effectively enhanced in air.Besides,a post-annealing process is also applied to improve flux trapping ability of SmBCO bulks.As a result,we obtain SmBCO bulks with trapped field of 0.6 T,which is reasonable good for air-processed SmBCO bulks by TSMG.This work presents a novel approach to fabricating air-processed SmBCO superconductors with high performance in a simple and convenient way by oxygen vacancy control.The CRCMG method should be universally applicable for other LREBCO systems.Moreover,the CRCMG method is also supposed to be taken for further application in synthesizing other functional oxide materials with the tunable cation non-stoichiometry.