High and medium entropy nitrides are an emerging and exciting class of materials. This especially applies for the field of superconductivity, in which the dependence of the transition temperature T_C on the concentration of incorporated nitrogen x shows different courses and has been investigated so far in only a small number of cases.

In our study we have investigated the impact of N incorporation into NbTaHfTiZr high entropy (HE) alloy films and compare the obtained results with those on other HE nitrides with a various N concentration [1,2]. The analysis of the results shows that the T_C vs x course, as well as the T_C enhancement, in HE nitrides strongly depend on the valence electron concentration (VEC) of the initial HE alloys, as a higher VEC accelerates the tendency to form the superconducting fcc crystal structure of nitrides, and is less sensitive to the localization of mobile electrons in initial HE alloys due to their bonding to incorporated N atoms. However, it turns out that also other parameters, as the atomic size difference of the metallic constituents and their affinity towards nitrogen, have to be considered.

[1] R. Shu et al., Stoichiometry effects on the chemical ordering and superconducting properties in TiZrTaNbN_x refractory high entropy nitrides, Ann. Phys. 536 (2023) 2300470.

[2] G. Pristáš et al., Multiple transition temperature enhancement in superconducting TiNbMoTaW high entropy alloy films through tailored N incorporation, Acta Mater. 262 (2024) 119428.