SEARCH · Engineering Papers

Results for “Hf4N3”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

3 records

All sources NASA NTRS DOE OSTI

DOE OSTI2020

Materials Data on Hf4N3 by Materials Project

Hf4N3 is MAX Phase-derived structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three Hf4N3 sheets oriented in the (0, 0, 1) direction. there are four inequivalent Hf sites. In the first Hf site, Hf is bonded to six N atoms to form a mixture of distorted corner and edge-sharing HfN6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 2°. There are three shorter (2.29 Å) and three longer (2.32 Å) Hf–N bond lengths. In the second Hf site, Hf is bonded in a distorted T-shaped geometry to three equivalent N atoms. All Hf–N bond lengths are 2.23 Å. In the third Hf site, Hf is bonded in a distorted T-shaped geometry to three equivalent N atoms. All Hf–N bond lengths are 2.29 Å. In the fourth Hf site, Hf is bonded to six N atoms to form a mixture of corner and edge-sharing HfN6 octahedra. There are three shorter (2.22 Å) and three longer (2.27 Å) Hf–N bond lengths. There are three inequivalent N sites. In the first N site, N is bonded to six Hf atoms to form a mixture of corner and edge-sharing NHf6 octahedra. The corner-sharing octahedral tilt angles are 2°. In the second N site, N is bonded to six Hf atoms to form a mixture of corner, edge, and face-sharing NHf6 octahedra. The corner-sharing octahedral tilt angles are 47°. In the third N site, N is bonded to six Hf atoms to form a mixture of corner, edge, and face-sharing NHf6 octahedra. The corner-sharing octahedra tilt angles range from 2–47°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Hf4N3 by Materials Project

Hf4N3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Hf sites. In the first Hf site, Hf is bonded to five N atoms to form a mixture of edge and corner-sharing HfN5 square pyramids. There are one shorter (2.18 Å) and four longer (2.27 Å) Hf–N bond lengths. In the second Hf site, Hf is bonded in a square co-planar geometry to four N atoms. There are two shorter (2.27 Å) and two longer (2.28 Å) Hf–N bond lengths. There are two inequivalent N sites. In the first N site, N is bonded to six Hf atoms to form a mixture of edge and corner-sharing NHf6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second N site, N is bonded to six Hf atoms to form a mixture of edge and corner-sharing NHf6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Phase composition of polycrystalline HfNx (0.45 ≤ x ≤ 1.60) and effects of low-energy ion irradiation on microstructure, texture, and physical properties

We have investigated the phase composition of HfNx as a function of x and the effects of low-energy ion irradiation on the microstructure and physical properties of polycrystalline layers grown on SiO2 at 350 °C by ultrahigh vacuum reactive dc magnetron sputtering of Hf in mixed N2/Ar discharges. X-ray diffraction and Rutherford backscattering spectrometry results show that the phases obtained in polycrystalline HfNx layers with increasing x are hcp-structure α-Hf:N (x ≲ 0.6); multiphase mixtures consisting of α-Hf, NaCl-structure δ-HfN, rhombohedral ɛ-Hf3N2, and/or ζ-Hf4N3 (0.6 ≲ x ≲ 0.9); δ-HfN single phase (0.9 ≲ x ≲ 1.3); and mixtures of δ-HfN and higher nitrides (x ≳ 1.3). HfNx layers with 0.9 ≲ x ≲ 1.2 grown under mild ion irradiation (incident ion energy Ei ≃ 7 eV and ion-to-Hf flux ratios Ji/JHf = 1−3) are underdense with mixed orientation, low in-plane stress, and rough surface morphology due to limited adatom mobilities resulting in kinetic roughening and atomic shadowing during film growth. However, the use of intense ion irradiation (Ei = 25 eV and Ji/JHf = 4−20) results in HfNx layers, which are fully dense with strongly 111-oriented texture, compressive in-plane stress, and smooth surfaces due to ion irradiation enhanced adatom surface mobilities. In addition, the latter films have lower resistivity and higher hardness. For stoichiometric δ-HfN layers, ρ decreases from 69.7 to 35.2 μΩ cm and H increases from 22.1 to 27.4 GPa, with increasing ion-irradiation intensity. However, for HfNx layers with 1.2 ≲ x ≲ 1.6, the correspondingly higher steady state atomic N surface coverages during deposition alter growth kinetics in favor of 001 texture with a fully dense structure and compressive in-plane stress.

Materials Science↗