Industrial scale HP-HT synthesis of hard and wear resistant c-Zr$_{3}$N$_{4}$

We present a large scale high-pressure high-temperature (HP-HT) synthesis of hard and wear resistant cubic zirconium nitride having Th$_{3}$P$_{4}$-type structure, c-Zr$_{3}$N$_{4}$. This material, also available as well-adhesive coatings with exceptional wear resistance, represents a compound competitive to diamond and c-BN with respect to machining of low-carbon steels and other ferrous alloys. We obtained c-Zr$_{3}$N$_{4}$ powder at pressures as low as 6.5 GPa and temperatures of 1400-1600 $^{\circ}$C from nanocrystalline Zr$_{3}$N$_{\mathrm{4+x}}$ precursor using a belt-type apparatus - a static HP-HT device widely employed for the commercial production of diamond and c-BN. The HP products are characterized in details by means of powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy and combustion elemental analysis. In addition to major polycrystalline c-Zr$_{3}$N$_{4}$, we unveil the formation of a quaternary compound c-(Zr$_{\mathrm{1-x}}$Ta$_{\mathrm{x}})_{3}$(N$_{\mathrm{1-y}}$O$_{\mathrm{y}})_{4}$ which indicates the possibility of doping of c-Zr$_{3}$N$_{4}$, thus introducing it for practical application as a multifunctional material. Moreover, we consider ways of cementing the c-Zr$_{3}$N$_{4}$ powders (similar to cemented tungsten carbides) which would allow economic fabrication of large bodies based on this compound.