High‐Pressure Synthesis of Tantalum Nitride Having Orthorhombic U₂S₃ Structure

Abstract

Among binary compounds, there is a high potential for discovery of novel members (polymorphic phases or compounds) of the nitrides of transition metals group due to a pronounced dependence of the oxidation state of the metals (M) on pressure. The power of high pressure–high temperature (HP‐HT) route for synthesis of binary nitrides has already been demonstrated by the discovery of cubic nitrides of the group 4 and 14 elements, of crystalline polymorphs of P3N5, and by reports on formation of four noble metal nitrides. It is anticipated that such HP products exhibit, in addition to enhanced elastic and mechanical behavior, other functional properties making them interesting for industrial applications. Here, HP–HT synthesis research is extended to nitrides of group 5 elements, resulting in the discovery of a novel hard tantalum nitride, exhibiting U2S3 structure: η‐Ta2N3 (Pbnm, a = 8.1911(17) Å, b = 8.1830(17) Å, c = 2.9823(3) Å). The stoichiometry is supported by two independent means, verifying that η‐Ta2N3 is the first thermodynamically stable transition metal nitride with a N:M ratio exceeding 4:3. Due to its high hardness and peculiar texture (needle‐like and granular crystallites), η‐Ta2N3 may find practical applications as a hard fracture resistant material.

The effect of structure and phase transformation on the mechanical properties of Re2N and the stability of Mn2N

“…The covalent bond formed between transition metal and anions is strong enough to inhibit creation and movement of dislocations, greatly improving the mechanical properties. Recently synthesized Ta 2 N 3 [5][6][7] has demonstrated a Vickers hardness of H V (0.5) = 16 GPa with a significant volume fraction porosity of about 10% and a peculiar texture, suitable for hard and fracture-resistance applications. In addition to the nitrides formed by transition metals of groups IV-VI, PtN 2 , [8,9] IrN 2 [9,10] and OsN 2 [10] being ultraincompressible have also been successfully synthesized.…”

Stability and Strength of Transition-Metal Tetraborides and Triborides

“…The suggested compounds include 5d transition metals diborides (e.g., OsB 2 [4] and ReB 2 [5]) and nitrides such as PtN [6], IrN 2 [7] and η-Ta 2 N 3 [8,9]. Although some of these materials have high elastic moduli [4,5], the experimentally determined loadinvariant hardnesses are typically below 30 GPa.…”

Mechanical Property of Composite Material Based on Map-Reduce Model

“…The rise of first principle calculations based on quantum mechanical techniques takes a prominent place in computational material science with the help of supercomputers [4]. The movement towards creating a material database using simulation opens a new way of seeking and designing new materials [5][6][7][8]. Such movement is also occurring in the field of catalysts where desired chemical reactions are evaluated using first principle calculations [9][10].…”