Comparative study of YBCO powder prepared by sol gel and solid state reaction processes

Full text: Extensive research activities are being carried out on high temperature superconducting YBCO to yield highest critical temperature (94 K). To achieve this purpose, we try to yield high homogeneous, pure powder by using two processes and compare the phenomena, including particle size of obtain powder. First one was solid state reaction process, using Y2O3, BaCO3, CuO as precursors then used mortar and pestle to mill them in stoichiometric ratio 1:2:3. The powder was calcined at 814 C in air for 24 h twice. The compound pressed into pellet in 10 Ton and sintered in an oxygen atmosphere at 930 C for 36 h and annealed at 630 C for 5 h and 550 C for 5 h followed by slow cooling at the rate of 1 C min-1 until room temperature. Second one was sol gel process using metal nitrate precursors. Stoichiometric amount of Y:Ba:Cu nitrate in ratio 1:2:3 were solved separately in distilled water then citric acid was added as needed (for each equivalent gram of metal nitrate add one equivalent gram of citric acid) . Ethylenediamin was added drop wised into the solution constant stirring until pH reached 7. Water was evaporated from the solution at 80 C until it became a viscous purple gel. The obtained gel was heated in an oversized baker up to 520 C for 2 h. Then powder was calcined at 900 C for 22 h at air. Pellet was sintered at 930 C for 19 h and annealed at 630 C for 2 h and slowly cooled down to room temperature at rate of 1 C/min. To compare the result one pellet was sintered with first initial program. Then the resulted products were characterized and compared grain size, phase purity and elemental component by SEM, XRD, EDS. Also TGA and DTA curves were used to compare these two processes. We find sol gel method results more pure, homogeneous, nanosized powder at low calcinations temperature and less time. (authors)