Rapid and Scalable Synthesis, Structure, and Physical Properties of Solid-Solution Layered Titanium Niobium...

We demonstrate rapid, scalable synthesis of solid-solution layered transition metal carbosulfides, Ti _x Nb_2-x SC (0 ≤ x ≤ 2). Thermogravimetric analysis confirmed superior thermal stability of Ti₂SC vs Nb₂SC; oxidation of Nb₂SC in air (750 °C) produced an accordion-like sulfur-bearing niobium oxide. Room-temperature X-ray diffraction and temperature-dependent neutron diffraction revealed linear contraction of lattice parameters with increasing Ti content. Strong anisotropic thermal expansion behavior arises from metallic basal planes vs nonmetallic M-S bonds, with Nb₂SC showing larger volumetric expansion than Ti₂SC. Specific heat measurments confirm that Ti₂SC is stiffer than Nb₂SC. In both thermal expansion and specific heat, nonmonotonic behaviors are linked to the critical role of Ti/Nb mixing. SQUID measurements show diamagnetic shielding in high-Nb samples, which, lacking an anomaly in specific heat, is ascribed to trace, percolating superconducting impurities rather than bulk superconductivity.