Blucher Proceedings V Encontro Científico de Física Aplicada Investigation of the influence of grain boundary on the magnetic properties of superconducting ceramics of Sm-123 Pinto, J. N. O. 1 ; Passos, C. A. C. 1 ; Orlando, M. T. D. 1, ; Rouver, A. N. 1 1 Programa de Pós-Graduação em Engenharia Mecânica, Universidade Federal do Espírito Santo, Vitória, ES, Brasil [~][/~][~][/~][~] [/~][~] [/~]Abstract Samples of SmBa 2 Cu 3 O 7-d (Sm-123) were prepared by the technique of solid vapor reaction with three different procedures. The samples were subjected to preliminary heat treatment, whose level was 960 ° C for 24 hours, which was repeated 7 times for sample A. Then they were subjected to further heat treatment at 1060°C level at which the samples A and B had a synthesis time of 72 hours, and sample C of 30 minutes. Then, the samples were cooled naturally to 520°C for oxygenation process. All samples were characterized by XRD, SEM and ac magnetic susceptibility measurements. SEM's of different average sizes for each sample junction, which influenced the ac magnetic susceptibility measurements. Keywords: superconductor, SmBaCuO, ceramic. 1. Introduction The transport properties of polycrystalline superconductors are limited due to grain boundaries (intergrain regions) and defects within the grains (intragrain regions) such as point defects, dislocations, stacking faults, cracks, etc. Understanding and control of the microstructure are necessary to improve the physical properties of granular superconductors and their applications. With this aim in mind, some researchers have optimized synthesis route of samples as reported in Ref [1-5]. The results indicated an upgrade of development and quality control of Sm-123 ceramic. Moreover, this material exhibits high J c under magnetic fields (peak effect) [1,2,5] which is important parameter for type inductive SFCL, motors and maglev transportation [3]. Because of the improvement on the properties of Sm-123, the replacement of YBa 2 Cu 3 O 7-d (Y-123) by Sm-123 might drastically improve the performance in practical applications [1-3]. 2. Synthesis of samples Three samples of SmBa 2 Cu 3 O 7-d , labeled as A, B and C were prepared as described elsewhere [6]. It is important to emphasize that the precursor of sample A was heated 7 times while the others samples were treated only one time. Moreover, others parameters for synthesis also were as displayed in the Table 1. Table 1: Parameter of synthesis of the ceramic samples. Sample Temperature Time Fluxo de O 2 A 1060°C 72h 30 bubbles /min B 1060°C 72h 30 bubbles /min C 1060 C 0.5h 60 bubbles /min 3. Characterization of samples All the samples were characterized by X ray powder diffraction. The phases identified were the orthorhombic and tetragonal structures of Sm-123 with some peaks associated to residual phase of BaCuO 2+x as shown in Table 2. Table 2: Global analysis of X-ray diffraction of the samples with different thermal treatments. Fases A B C Ortorrombic 74 91 89 Tetragonal 10 6 7 6 2 2 Unidentified 10 1 2 These samples were also analysed by Scanning Electron Microscopy (SEM). Details of the grain morphology can be observed in the SEM image in Figures 1. Using this image of sample A, a histogram of the grain boundary size was done. This procedure was also used for samples B and C. These histograms were then analysed in the framework of gamma density distribution function: where λ and η determine the distribution scale and distribution shape, respectively. This function is often used on models which describe physical quantities are taken positive values. The average junction size was carried out and it is shown in Table 3.