Test of Tc-Predictions Using the Rigid Band Model for Refractory Compounds
B1-compounds are particularly suitable to test Tc-predictions, as they form continuous solid solutions with intermediate properties reflecting the changing number of valence electrons (VE). Thin films of the Nb1-xMoxC, Nb1-xMoxC1-yNy and MoCxNy systems were prepared by sputtering. There are serious discrepancies between theory and the experimental results. In particular, the predicted minimum at 10.45 VE was not observed. It was possible to prepare Nb0.3Mo0.7C with 9.7 VE stoichiometrically. Instead of the expected Tc of 17 K only 13 K was measured. In the NbCl-yNy, Ti1-xNbxN and Ti1-xNbxC1-yNy systems for around 9.7 VE a Tc of up to 17.3 K is observed in agreement with theory. However, where theoretically a narrow maximum is predicted, high Tc values are observed for a wide range of VE.
KeywordsValence Electron Refractory Compound Continuous Solid Solution Phonon Softening Narrow Maximum
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