Properties in reactive structure materials. ZrW${}_2$ and HfW${}_2$ - high melting temperatures, densities, hardness, and exothermic ignition energies

ZrW${}_2$ and HfW${}_2$ were prepared by melting the constituent elements in an arc-furnace. By cooling through perictectic phase lines above approximately 2000 °C, samples of the nominal 1:2 composition were obtained as products consisting of two phases, of which approximately 95 % adopts the MgCu${}_2$ type structure and 5 % the W structure. In ZrW${}_2$ and in HfW${}_2$, the MgCu${}_2$ type structure enables efficient topological compact spacefilling of the smaller W atoms into the cavities of the three-dimensional net constructed by the larger tetravalent metals Zr and Hf. Correspondingly, very dense and hard alloys are obtained which burn at a crash in air in a strong exothermic ignition reaction. These materials are non-toxic. (© 2020 The Authors. Published by Wiley‐VCH GmbH)