Name: Janaína Simões Lima
Type: MSc dissertation
Publication date: 31/07/2017

Namesort descending Role
Carlos Augusto Cardoso Passos Advisor *

Examining board:

Namesort descending Role
Carlos Augusto Cardoso Passos Advisor *
José Luis Passamai Junior External Examiner *
Marcos Tadeu DAzeredo Orlando Internal Examiner *

Summary: Samples of SmBa2Cu3O7-δ polycrystalline ceramics (Sm-123) were prepared by solid-state reaction and doped with different concentrations of MnRe . The samples were named: Sample A without dope, Sample B with 0,20% of doping, Sample C with 0.50% of doping, Sample D with 1,0% of doping and Sample E with 1,5% of doping. After mixing, each of the samples was compacted in identical format and subjected to a uniaxial pressure of 1 ton for 1 minute and thereafter under 1,5 tons for a further 1 minute. The heat treatment of calcination occurred at 930ºC for 40 hours. Afterwards, the samples were submitted to the synthesis thermal treatment with a plateau of 1060ºC during a period of 30 minutes, being cooled to 520ºC for 24 hours. After the thermal treatment of synthesis a new heat treatment was carried out, the only difference between the last two treatments was the final cooling rate, the first synthesis being at 5ºC/min and the second synthesis at 1ºC/min. Both syntheses occurred with an oxygenation of 60 bubbles/minutes. The samples were characterized by X-ray diffraction and SEM. The X-ray results indicated the predominance of the Sm-123 phase with tetragonal and orthorhombic crystalline structure, as well as the appearance of some impurities. From the X-ray results, the network parameters of the Sm-123 phase with orthorhombic crystal structure and the tetragonal structure were found; Sample B presented slightly lower unit cell volume compared to the values of the other samples. According to the analysis of scanning electron microscopy, the ceramics didn't present micro-cracks. In addition, the Ca2MnReO6 dopant element influenced grain growth. The average junction sizes were 2,81 μm (sample A), 2,26 μm (sample B), 2,29 μm (sample C), 2,33 μm (sample D) and 2,12 μm (sample E). The micrographs also revealed that doped ceramics exhibit particle agglomerates in regions of boundary grains and pore. In our opinion these particles are Ca2MnReO6 dopant.

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