Lattice parameters, thermal expansion coefficients and densities of Nb, and of solid solutions Nb–O and Nb–N–O and their defect structure

The temperature expansivities (by the X‐ray method), the densities and the defect structures of the 3 cubic nonstoichiometric compounds (solid solutions) of the composition Nb, NbO 0.017 and NbN 0.90 O 0.013 (nitride) were determined. The lattice parameters a at 25°C were: 3.3004, 3.3047 and 4.3855 Å; the linear expansion coefficients, α, between 15 and 65°C were 7.6, 8–65 and 7–75 × 10–6°C −1 respectively. As the temperature is increased, α undergoes several changes in magnitude. The cubic nitride started to decompose at about 850°, with a loss of N (decrease of α). The structure of the oxygen‐poor Nb is free from vacancies and interstitial atoms within the limits of error; that of the oxygen‐rich Nb contains interstitial atoms on additional sites in a concentration of 1.9%, and the nitride contains vacant sites in both sublattices (4.8% total).