Properties of ceramics in the system ZrB2–Ta5Si3

Ceramics in the system ZrB2–Ta5Si3 were studied as candidates for the development of new ultra high-temperature ceramic materials. The ceramics were prepared by hot pressing at 1900–2200 °C in He. Mutual additions of ZrB2 and Ta5Si3 even in small amounts had significant densifying effects due to chemical interactions and solid solubility between the components, which have not been reported in the literature. Materials containing between 8 and 30 vol% Ta5Si3 exhibited less oxidation than pure ZrB2, which is the result of phase separation in surface borosilicate glass induced by Ta2O5. For higher concentrations, oxidation resistance substantially decreased with increasing Ta5Si3 content. The trend in the oxidation behavior of the materials showed significant dependence on the volume of oxidation products. Ceramics containing up to 10 mol% (30 vol%) Ta5Si3, which showed the highest oxidation resistance, also had the highest strength and hardness in the system, and are of interest for high-temperature structural applications in oxidizing environments.