[NiEn₃](MoO₄)_0.5(WO₄)_0.5 Co-Crystals as Single-Source Precursors for Ternary Refractory Ni-Mo-W Alloys

The co-crystallisation of [NiEn₃](NO₃)₂ (En = ethylenediamine) with Na₂MoO₄ and Na₂WO₄ from a water solution results in the formation of [NiEn₃](MoO₄)_0.5(WO₄)_0.5 co-crystals. According to the X-ray diffraction analysis of eight single crystals, the parameters of the hexagonal unit cell (space group P-31c, Z = 2) vary in the following intervals: a = 9.2332(3)-9.2566(6); c = 9.9512(12)-9.9753(7) Å with the Mo/W ratio changing from 0.513(3)/0.487(3) to 0.078(4)/0.895(9). The thermal decomposition of [NiEn₃](MoO₄)_0.5(WO₄)_0.5 individual crystals obtained by co-crystallisation was performed in He and H₂ atmospheres. The ex situ X-ray study of thermal decomposition products shows the formation of nanocrystalline refractory alloys and carbide composites containing ternary Ni-Mo-W phases. The formation of carbon-nitride phases at certain stages of heating up to 1000 °C were shown.