Stability and oxidation properties of RE–α-Sialon ceramics (RE = Y, Nd, Sm, Yb)
1998 (English)In: Journal of The American Ceramic Society, ISSN 0002-7820, Vol. 81, no 6, 1461-1470 p.Article in journal (Refereed) Published
Oxidation studies of hot-pressed RE–α-sialons, REx-Si12−4.5xAl4.5xO1.5xN16−1.5x (with x = 0.40 for RE = Nd, Sm,Yb; and x = 0.48 for RE = Y) were carried out in oxygen in a TG apparatus for ca. 20 h. Very good oxidation resistance was found for the Yb-doped samples, with parabolic rateconstants Kp ≈ 0.09 × 10−6–3 × 10−6 mg2 cm−4 s−1 in the temperature range 1250–1350°C. The promising performance of this material was corroborated by long-term oxidation experiments (5 days) in air at 1350°C. Although the oxidation kinetics can be described by simple equations related to the parabolic rate law (e.g., the arctan equation, ΔW/Ao = α·arctan(bt)½+ct½), the oxidation process in these materials is likely to be complex. The significantly lower oxidation resistance of the RE = Nd, Sm doped α-sialons, especially at higher temperatures, is related to the formation of melilite, RE2Si3−yAlyO3+yN4−y (y ≈ 1), in these systems. The melilite phase is also responsible for the thermal instability of the Nd– and Sm–α-sialons.
Place, publisher, year, edition, pages
1998. Vol. 81, no 6, 1461-1470 p.
IdentifiersURN: urn:nbn:se:liu:diva-54191DOI: 10.1111/j.1151-2916.1998.tb02504.xOAI: oai:DiVA.org:liu-54191DiVA: diva2:300901