Effect of neutron irradiation on microstructure and strength of Bi-2212 phase superconductor

The sustainability of superconductors when exposed to radiation environment is vital for the materials to be used as components and devices in nuclear reactors. In this investigation, TRIGA MARK II research reactor with neutron flux of 2.00 × 10¹¹ / cm²s was used as the neutron source to study the effect of neutron irradiation on microstructure and physical strength of Bi₂Sr₂CaCu₂ (Bi-2212) superconductor. Results between non-irradiated and irradiated samples have been analyzed with respect to phase formation, microstructure and strength of the superconductor. The bulk samples were synthesized using the conventional solid-state reaction method. Molar ratio of Bi₂O₃, Sr₂CO₃, CaCO₃, and CuO were mixed according to its ratio into composition of Bi:Sr:Ca:Cu = 2:2:1:2. The powder were palletized and sintered at 840°C for 48 hours. Characterization of the samples was done via X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The XRD patterns for the non-irradiated and irradiated samples show well-defined peaks of which could be indexed on the basis of a Bi-2212 phase structure. XRD patterns also indicate that irradiation did not affect the Bi-2212 superconducting phase. From observation of the XRD pattern and microstructure, there is indication that a small amount of Bi-2212 is decomposed into Cu₂O and other impurities while a significant amount of un-reacted Bi-2212 particles embedded at the grain boundaries. For the non-irradiated samples, the microstructure was found to be more textured and thus enhanced the strength of the samples. For the neutron irradiated samples, the results show disorganization of grains orientation and formation of porous structure that led to reduction in overall strength of the Bi-2212 superconductor.