Nitrides: Transition Metal Solid‐State Chemistry

Abstract

Both basic properties and properties interesting for applications of transition metal nitrides are presented in this article. Starting from crystal chemistry, bonding, and preparation, the article also briefly discusses the analytical chemistry of chemical and physical nitrogen analysis and standardization as well as thermodynamics. Portions of phase diagrams of group 4–6 transition metals with nitrogen are presented. A substantial part is devoted to the solid‐state properties because they make nitrides interesting for applications. The presentation of these properties includes hardness, thermal expansion, nitrogen diffusivity, thermal properties, electrical conductivities, superconductivities, and elastic properties. Several of these properties are given as a function of temperature and composition. A final part shows examples for application of transition metal nitrides because of their extraordinary properties. The topic of transition metal nitrides is closely connected to that of metal carbides.

Determining the Nitrogen Content in (Oxy)Nitride Materials

“…The process at the origin of the combustion technique’s devices is briefly described in literature [9,20] (Figure 2). …”

“…This micro-analysis technique is considered to have the highest reproducibility and accuracy provided the resolution of a few microns is sufficient [9] and the standards are appropriate [32]. As light elements can be analyzed starting from boron, WDS looks suitable to analyze (oxy)nitride thin films.…”

“…His method was extended to a large panel of materials: liquid and solid, organic and inorganic. When nitrogen is under an organic form, the experimental protocol involves three steps: dissolution in acids to obtain mineral nitrogen, distillation, and titration [ 9 , 13 ]. The first step consists in heating and degrading the organic nitrogen into an ammonium salt in the presence of concentrated sulfuric acid and catalysts (CuSO 4 , KSO 4 ).…”

“…However, finding calibration standards with high nitrogen contents (10–20 wt% N) may be quite challenging. To date only a few papers have raised the issue of nitrogen analyses [ 8 , 9 , 10 ].…”

Extremely hard and tough high entropy nitride ceramics

“…The hardness and toughness of TMN and related solid solutions with FCC structure are interrelated functions of electron valence. As the valence electron concentration (VEC) is minimized, the hardness is maximized (usually at VEC = 8.4); oppositely, when the valence is maximized, the toughness is minimized (at VEC ≥ 10) 7,11,12 as the result of antibonding state occupation-induced lattice softening 13,14 . For example, in δ-TiN 1−x , the microhardness maximum occurs at δ-TiN 0.67 , which corresponds to 7.3 valence electrons 14 .…”