Structure evolutions of the polymer derived medium-/high-entropy metal carbides

Ceramic powders with low oxygen content are highly demanded in monolithic ceramics. In this work, a series of medium-/high-entropy ceramic (HEC) particles, including (Zr0.25Ta0.25Nb0.25Ti0.25)C, (Zr0.2Ta0.2Nb0.2Ti0.2W0.2)C, (Zr1/6Ta1/6Nb1/6Ti1/6W1/6Hf1/6)C (Zr1/7Ta1/7Nb1/7Ti1/7W1/7Hf1/7V1/7)C, and (Zr1/8Ta1/8Nb1/8Ti1/8W1/8Hf1/8V1/8Mo1/8)C, were successfully fabricated by the polymer-derived ceramic (PDC) route. The structure evolutions of the precursor demonstrated that HEC particles obtained at 1800 °C possessed a single phase and rock-salt structure. All the samples had the similar microstructures (hillock structure) and a low oxygen impurity content (less than 2.00 wt%). The results also demonstrated that the as-obtained HEC particles had a disordered distribution of elements from nanoscale to microscale. This work proved a new method to fabricate the HEC powders with low oxygen impurity content and the HEC precursors for further obtaining the nanofibers or ceramic matrix composites.