Abstract: Hard and wear-resistant conductors (HWCs) have important applications in the next-generation sliding electrical contacts. However, Cu- and Pt-based alloys, two commonly used HWCs, have very low hardness despite their good electrical conductivity. In this letter, we integrate high hardness, wear resistance, and good electrical conductivity in one material by introducing high-plasma-energy (E_p) heterogeneous metals (e.g., Ag or Ta) to transition metal nitrides (e.g., HfN). The obtained solid solution films (such as Hf_0.92Ag_0.08N) not only have the good electrical conductivity as traditional HWCs (such as Pt-Ir alloy) but also exhibit much higher hardness and wear resistance than traditional HWCs. Introducing Ag and Ta can improve the hardness and wear resistance of HfN almost equally, but the introduction of Ag can provide better electrical conductivity. This is because the introduction of Ag induces a synergistic effect of E_p and relaxation time (τ), while the introduction of Ta results in a competitive effect of E_p and τ. Through the combination of first-principles calculations and experiments, we explain the physical mechanisms of these two effects and draw a map of candidate materials with the synergistic effect. Therefore, the new HWC design strategy proposed in this study not only broadens the range of applications for transition metal nitrides but also breaks the bottleneck of integrating high hardness, high electrical conductivity, and wear resistance.

Key words: Transition metal nitrides, Heterogeneous metals, Hard and wear-resistant conductors, Plasma energy