Figure 5
From: Discovery of Superconductivity in Hard Hexagonal ε-NbN
(A) Average measured Vickers hardness (HV) for polycrystalline hexagonal ε-NbN under different applied loads, indicating that the tendency of hardness decreases and becomes weak with large loads; SEM image, crystal structure and a typical Vickers indentation image at a load of 9.8 N are displayed as insets. (B) Comparing the Vickers hardness of hexagonal ε-NbN with those for the rock-salt structured cubic NbN, HfN and ZrN reported by Chen et al. (ref. 4).
