Structural-Microstructural Characteristics and its Correlations with the Superconducting Properties of in-situ PIT Processed MgB$_{2}$ Tapes with Ethyltoulene and SiC Powder added

The structure and microstructures of pure MgB$_{2}$, ethyltoulene and ethyltoulene + SiC added MgB$_{2}$ tapes have been investigated by using selected area electron diffraction, bright field, dark field and high resolution electron microscopy. As reported, the Jc values of the ethyltoluene and ethyltoulene + SiC added MgB$_{2}$ tapes are much higher than the pure MgB$_{2}$ tape sample. Analysis of the microstructures shows that pure MgB$_{2}$ tape~ sample consist of grains of 100-200nm. With the addition of ethyltoulene and ethyltoulene + SiC to the starting powder of \textit{in situ} processed MgB$_{2}$ tapes, the grain size decreases drastically to an average size of about 20-50nm. The higher Jc value of~ the ethyltoulene and ethyltoulene + SiC added MgB$_{2}$ tapes as compared to the pure MgB$_{2}$ tapes has been attributed~to the decrease in grain size and better connectivity of the grains and also presence of pinning centers as some precipitates and Mg$_{2}$Si particles of size less than 100nm.