•Spherical bulk ε-Fe3−xCoxN has been prepared through HPSSM reactions.•Both ε-Fe3N and ternary ε-Fe3−xCoxN have metallic Fe0 character.•There is no metallic form Co0 in the ternary ε-Fe3−xCoxN nitrides.Spherical-like bulk ε-Fe3−xCoxN (x = 0.0, 0.25, 1.95) alloys have been synthesized through high-pressure solid-state metathesis (HPSSM) reactions at 5 GPa and 1673 K, employing Fe2O3, CoO and hBN as reaction precursors. The as-prepared nitrides ε-Fe3−xCoxN crystallizes isostructural to ε-Fe3N as evidenced by powder X-ray diffraction (RXPD) and high-resolution transmission electron microscope (HRTEM). A detailed X-ray photoelectron spectroscopy (XPS) study of the as-prepared nitrides reveal that both binary ε-Fe3N and ternary ε-Fe3−xCoxN have metallic form Fe0 character due to the diffusion of nitrogen from the idea 2c interstitial site, but no evidence for the exists of metallic form Co0 in the ternary ε-Fe3−xCoxN nitrides. We also find that the enhancement of Ms and Hc with the increase of Co at% in ε-Fe3−xCoxN may be due to the altered micro structural and exchange interactions.

•Well-crystallized plate-like Re3N crystals were synthesized through HPSSM reaction in LVP at 14 GPa and 1973 K.•The vibrational properties of Re3N crystals were studied by high-pressure Raman spectroscopy in DAC up to 20 GPa.•The mode-Grüneisen parameters for Raman modes of Re3N were determined experimentally for the first time.Well-crystallized plate-like Re3N crystals were synthesized through a high-pressure solid-state metathesis (HPSSM) reaction in large volume press (LVP) at 14 GPa and 1973 K. The vibrational properties of Re3N crystals were studied by high-pressure Raman spectroscopy in diamond anvil cell (DAC) up to 20 GPa. The mode-Grüneisen parameters for Raman modes of Re3N were determined experimentally, which were found substantially being larger than previously calculated values.

•The Li ions undergo positional disordering along the structural channels on heating.•An anomalous maximum in the bandwidths of the Li ions related modes is observed.•A model is used to describe the linewidth of a phonon.•The activation energy of Li ions is about 0.5 eV.The temperature dependence of Li ions behavior of γ-LiAlO2 has been studied from 78 to 873 K. On heating, the Li ions underwent positional disordering along the structural channels, with the Li ions related modes at 220, 366 and 400 cm−1 broadening and weakening dramatically. An anomalous maximum in the bandwidths of the Li ions related modes is observed. It should be apparent that there are at least two distinct thermally activated processes. A model suggested by Andrade and Porto is used to describe the linewidth of a phonon.

We report a general synthetic route to well-crystallized metal nitrides through a high-pressure solid-state metathesis reaction (HPSSM) between boron nitride (BN) and ternary metal oxide AxMyOz (A = alkaline or alkaline-earth metal and M = main group or transition metal). On the basis of the synthetic metal nitrides (Fe3N, Re3N, VN, GaN, CrN, and WxN) and elemental products (graphite, rhenium, indium, and cobalt metals), the HPSSM reaction has been systematically investigated with regard to its general chemical equation, reaction scheme, and characteristics, and its thermodynamic considerations have been explored by density functional theory (DFT) calculations. Our results indicate that pressure plays an important role in the synthesis, which involves an ion-exchange process between boron and the metal ion, opening a new pathway for material synthesis.