Role of Multi-Walled Carbon Nanotube Addition in Superconducting Properties of Bi2Sr2CaCu2O8+s Glass-Ceramic Superconductors

In this work, pure and with 1, 3, 5, 10, and 15 wt% multi-walled carbon nanotube addition Bi 2 Sr 2 CaCu 2 O 8+ s glass–ceramic materials have been investigated in terms of thermal, structural, microstructural, electrical, and magnetic properties. Multi-walled carbon nanotubes with a purity of 96% were used to enhance electrical transport properties. Thermal properties have been examined using differential thermal analysis. According to the differential thermal analysis, the multi-walled carbon nanotube addition reduced the melting temperature and slightly increased the crystallization activation energy of the BiSrCaCuO material. X-ray analyses showed that all samples have tetragonal symmetry and did not change with addition, but a small change in the c -axis is observed. Scanning electron microscope analyses showed no significant morphological change. The effect of the additive on the resistivity measurements was found to be limited, and zero resistance temperature increased up to a level of 5 wt% addition and then decreased drastically for higher addition cases. The hole concentration of the samples was calculated, and it was found that there was a shift towards the over-doped region with the addition. For the transport critical current density measurements, the highest increase of about 30 % was obtained for the sample with 5 wt% multi-walled carbon nanotube addition, but in high addition cases, significant losses were obtained. A similar situation occurred in magnetization versus magnetic field measurements, and the highest magnetization critical current density value obtained ˚was 4 . 1 × 10 6 A/cm 2 at 4.2 K in the 5 wt% multi-wall