Evaluation of rare‐earth element dopants (Sm and Er) on ablation resistance of ZrB 2 /SiC‐sintered billets

Abstract In this paper, how rare‐earth element dopants (samarium and erbium) affect the scale development of sintered ZrB 2 /SiC (ZBS) samples during ablation testing was investigated. ZBS billets with five different Sm to Er ratios, with a nominal total amount of 3 mol% dopant incorporated, were prepared by sintering in vacuum to 2000°C and subjected to 60 and 300 seconds ablation cycles. Differences in surface temperatures between ZBS samples with different dopant ratios suggests differences in spectral absorptance/emittance between each of the five compositions investigated. ZBS billets co‐doped with Sm and Er form a beneficial c 1 ‐(Sm/Er) 0.2 Zr 0.8 O 1.9 oxide scale as the majority phase, with some glassy phase observed. The crystalline c 1 ‐(Sm/Er) 0.2 Zr 0.8 O 1.9 oxide scale is more thermally stable than the m ‐ZrO 2 oxide scale typically formed in oxidized ZBS systems, resulting in a more adherent oxide scale to the unreacted material. The crystalline oxide scale and the amorphous phase are formed by a convection cell mechanism where the c 1 ‐(Sm/Er) 0.2 Zr 0.8 O 1.9 crystalline islands precipitate, grow, and coalesce.