Among transition metal nitrides, tungsten nitrides possess unique and/or superior c
hemical, mechanical, and t
hermal properties. Preparation of t
hese nitrides, however, is challenging because t
he incorporation of nitrogen into tungsten lattice is t
hermodynamically unfavorable at atmosp
heric pressure. To date, most materials in t
he W鈥揘 system are in t
he form of thin films produced by nonequilibrium processes and are often poorly crystallized, which severely limits t
heir use in diverse technological applications. Here we report synt
hesis of tungsten nitrides through new approac
hes involving solid-state ion exchange and nitrogen degassing under pressure. We unveil a number of novel nitrides including
hexagonal and rhombo
hedral W
2N
3. T
he final products are phase-pure and well-crystallized in bulk forms. For
hexagonal W
2N
3,
hexagonal WN, and cubic W
3N
4, t
hey exhibit elastic properties rivaling or even exceeding cubic-BN. All four nitrides are prepared at a moderate pressure of 5 GPa, t
he lowest among high-pressure synt
hesis of transition metal nitrides, making it practically feasible for massive and industrial-scale production.
Keywords:
tungsten nitride; hesis&qsSearchArea=searchText">high-pressure synthesis; ion exchange