Influência da temperatura de síntese nas propriedades física e mecânica do supercondutor SmBaCuO

Abstract

With the purpose of future application, polycrystalline ceramics of the type 𝑆𝑚𝐵𝑎2𝐶𝑢3𝑂7−𝛿 (Sm-123) were made in order to produce superconducting samples. Two preparation routes were used so that, in one case, the reagent was used in stoichiometric proportions and the other in which the mixture was non-stoichiometric. Through the solid state reaction, high purity reagents were mixed according to the stoichiometric equation of each route. The stoichiometric samples were calcined at levels of 930ºC and 960ºC varying from 20 to 80 hours in an open oven. They were also sintered at two different levels: 1060ºC for 72 hours and 520ºC for 24 hours in an oxygen atmosphere oven. For characterization, the samples were submitted to X-ray diffraction for quantification of crystalline structures, density test and hardness test. Calcination at 930ºC resulted in better formation of orthorhombic structure in 80 hours, while below that there was much more formation of the tetragonal structure. For 960ºC there was no great difference in time and in the formed structures. After sintering, in the 930ºC group, the 80-hour sample continued with better results in the formation of an orthorhombic structure, while the 960ºC group continued to present less orthorhombic structure than the tetragonal one. Density in both groups has a parabolic behavior in which it reaches a maximum and then decreases. The hardness also showed parabolic behavior in the A960 group, since it was not possible to perform the test on the A930 group, as the preparation in semi-automatic grinding and then polishing with DiaDuo 3 micro worked only for A960. For non-stoichiometric samples, only calcination was performed in an open oven at a level of 960ºC for 20, 60 and 80 hours. X-ray diffractions were made in each one and its crystal structure was quantified, which showed greater formation of orthorhombic structure and less tetragonal, being a possible route for making Sm-123 ceramics with greater presence of crystal structure.