Preparation of High-Entropy (Ti, Zr, Hf, Ta, Nb) Carbide Powder via Solution Chemistry.

High-entropy ceramics is a new class of materials having a great potential and wide application. The carbide of Ti, Zr, Hf, Ta, Nb is a typical member of this group. It has been synthesized mostly through blending, milling, and high-temperature solid-state reaction of metal carbide precursors for each metal. This route needs extremely high temperature (2300 °C), which makes it energy and technology demanding. We have developed a chemical route for high-entropy carbide powder that needs a synthetic temperature that is several hundred degrees Celsius lower. A solution of desired metal citrates with an excess of citric acid was converted into a metal oxide/active carbon nanocomposite. Starting from a solution enabled ideal mixing of precursors on a molecular level, allowing us to skip any milling and blending steps. The nanocomposite was treated in vacuum at 1600 °C, giving a phase-pure high-entropy carbide. The intermediate compounds and products were characterized by means of solid-state analysis.