| Popis: |
About eighty transition metal compounds comprising borides, carbides, nitrides, oxides, silicides, and germanides of metals of Groups 4A, 5A, and 6A were tested for superconductivity down to 1.20\ifmmode^\circ\else\textdegree\fi{}K, using a magnetic method. Among the specimens were most of the known compounds of the above type not examined magnetically for superconducting behavior by previous workers, and in all cases the structures were checked by x-ray diffraction analysis. The following eleven new superconductors were discovered, with the transition temperatures (\ifmmode^\circ\else\textdegree\fi{}K) shown in parentheses: ${\mathrm{W}}_{2}$B (3.10\ifmmode^\circ\else\textdegree\fi{}), ${\mathrm{Nb}}_{2}$C (9.18\ifmmode^\circ\else\textdegree\fi{}), ${\mathrm{Ta}}_{2}$C (3.26\ifmmode^\circ\else\textdegree\fi{}), ${\mathrm{Nb}}_{4}$${\mathrm{N}}_{3}$ (7.2\ifmmode^\circ\else\textdegree\fi{}), ${\mathrm{V}}_{3}$Si (17.1\ifmmode^\circ\else\textdegree\fi{}), ${\mathrm{V}}_{3}$Ge (6.01\ifmmode^\circ\else\textdegree\fi{}), ${\mathrm{Mo}}_{3}$Si (1.30\ifmmode^\circ\else\textdegree\fi{}), ${\mathrm{Mo}}_{3}$Ge (1.43\ifmmode^\circ\else\textdegree\fi{}), $\ensuremath{\alpha}$-Th${\mathrm{Si}}_{2}$ (3.16\ifmmode^\circ\else\textdegree\fi{}), $\ensuremath{\beta}$-Th${\mathrm{Si}}_{2}$ (2.41\ifmmode^\circ\else\textdegree\fi{}), and ${\mathrm{W}}_{3}$${\mathrm{Si}}_{2}$ (2.84\ifmmode^\circ\else\textdegree\fi{}). These compounds include the first superconducting germanides, ${\mathrm{V}}_{3}$Ge and ${\mathrm{Mo}}_{3}$Ge, which, together with ${\mathrm{V}}_{3}$Si and ${\mathrm{Mo}}_{3}$Si, crystallize in the cubic $\ensuremath{\beta}$-tungsten structure. The transition temperature of ${\mathrm{V}}_{3}$Si is apparently the highest known for any binary superconducting compound. |
