Preparation of YBCO superconductor samples by tube method (PITM), effect of Cd and Ga substitution on the system

In this study, YiBa2Cu307.s and Y0.5Xo.5Ba2Cu307.g (X=Ga, Cd) compounds were synthesied by Powder-In-Tube method and electrical and physical properties of system were investigated. After getting together the compounds that chemical formulas are given, they were mixed in order to have homogen and small granular size. This raw compound was calcinated to 970 °C. While the calcination process, oxygen gas was given to powder sample at 500 °C. Chemical compounds were put into 30 mm lenght and 5 mm diameter Ag tubes. All of the obtained samples were heated in oxygen atmosphere. YiBa2Cu307.5, Yo.5Cdo.5Ba2Cu307-8 and Yo.sGao.sBaaC^Ov-s samples were prepared under 3, 5, 9 tons and X-ray difractions, electical resistance, SEM and EDAX, analysis measurements were done. In the results of X-ray difraction, it is seen that samples which are prepared from YiBa2Cu307"g composition exhibit quite clear characteristic of YBCO peaks and as a conccqucncc of this, samples have high purity. Decrease in magnitude of peaks by effect of applied pressure was observed. In the Yo.sCdo.sBaaCu-sO?^ composition, peaks inwhich reside in different positions from those of YBCO system were seen in the structure. It was observed that Cd substitution into YıBaaCıijOy-ö, Y|Ba2Cıi307-s structures to multi-phase system and effect its superconductivity state worse. In the Yo.5Gao.5Ba2Cu307-8 composition, it was understood that Ga substitution in Yo.5Gao.5Ba2Cu307_s caused negative effects on superconductor phases and terminated its superconductivity state. In the result of resistance measurements, rcsirtancc of Y1Ba2C1i3O7.fi samples were maeasured under various magnetic field and it was understood that YıBa2Cıi307-s structure was in quite good quality and homogen. Superconductivity transition temperature (Tc) of this system was found to be 93 K. For the Cd and Ga substitution samples, it was seen that Ga substitution led structure entirely lose its superconductivity property. Beside that, it was seen that Cd substitution produced better results on the system than those of Ga substitution. After Cd dopping, it was observed that superconducting transition temperature varied in the range 85-90K. In the result of SEM and EDAX analysis, granular formation of classical YBCO and partial melted classical structuring were seen for YiBa2Cu307_5 composition. In the result of EDAX analysis, it was understood that the structure was in good quality and quite homogen. According to SEM results of Cd substitution samples, it was observed that partial melting on the surface of the samples was much more than that of the YBCO system and there existed very wide gaps between half melted areas. In the results of EDAX analysis of this system, it was understood that electrical properties were badly effected respect to YBCO system. According to SEM results of Ga substitution samples, worse results than those of Cd substitution system were obtained. Superconductivity was vanished in structure. Hence, complete granular structuring in approximiatly the same volume and different shape was took place in the structure. In the result of EDAX analysis of his system, it was concluted that Cu could locally remain in various areas without reacting any material. KEYWORDS: Powder-In-Tune method, YBCO, solid-state reaction method