Electrical and magnetic properties of silicon carbide composites with titanium and niobium carbide as sintering aids

Silicon carbide based composites with 30, 40 and 50 wt. % of of Ti and NbC as sintering additives were prepared by hot-press method. Molar ratio of Ti:NbC was kept at 1:1.8. The two step sintering was performed in order to avoid the squeezing out the melted titanium above 1668 °C. Composite powders were sintered at 1650 °C for 3 h and subsequently at 1850 °C for 1 h under mechanical pressure of 30 MPa in Ar atmosphere. XRD pattern confirmed the formation of (Ti, Nb)Css in the SiC matrix. Composite with 50 % of Ti-NbC phase showed the extraordinary electrical conductivity of 2.4 x 10⁵ S/m which was achieved by homogeneous distribution of Ti and NbC in SiC matrix and forming a continuous conductive network. Prepared composites show complex magnetic forming a continuous conductive network. Prepared composites show complex magnetic NbC admixing, as well as weak ferromagnetism probably coming from impurities contained in the initial powders. Samples with 30 and 40 wt. % of Ti and NbC exhibit superconducting state below 2 K.