Studies of Compounds for Superconductivity

A number of metal carbides, borides, nitrides, and a hydride, in the form of powders, have been examined for superconductivity down to 1.8°K using a magnetic method. The substances tested were TiC, VC, ZrC, TaC, WC, Zr${\mathrm{B}}_2$, Nb${\mathrm{B}}_2$, Ta${\mathrm{B}}_2$, WB, MoB, $\mathrm{Ti}{\mathrm{B}}_x$, Th${\mathrm{B}}_2$, LaN, CeN, NbN, and La${\mathrm{H}}_{2.45}$. All specimens were characterized by x-ray diffraction methods and, in most instances, by chemical analysis. Of these substances only NbN gave evidence for superconductivity. The results for NbN are in general agreement with the work of others. The results for TiC and VC are in agreement with those found by Meissner et al., using an electrical resistance method, while those for Ta${\mathrm{B}}_2$, Nb${\mathrm{B}}_2$, WC, and WB are in agreement with observations made by Matthias and Hulm using a magnetic method. On the other hand, ZrC, TaC, WC, and "zirconium boride" had previously been observed to exhibit superconductivity above 1.8°K by the electrical resistance method. The results for WC and MoB have recently been confirmed by Matthias and Hulm. The substances Th${\mathrm{B}}_2$, LaN, CeN, and La${\mathrm{H}}_{2.45}$ had not previously been examined for superconductivity.