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Duplex α,β‐Sialon Ceramics Stabilized by Dysprosium and Samarium
Author(s) -
Ekström Thommy,
Falk Lena K. L.,
Shen ZhiJian
Publication year - 1997
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1997.tb02830.x
Subject(s) - sialon , melilite , materials science , ceramic , mineralogy , composite material , crystallography , metallurgy , chemistry , spinel
Duplex αβ,‐sialon ceramics with a minimum volume fraction of residual intergranular glass have been prepared using Dy or Sm as the α‐sialon stabilizing element. These microstructures contained high aspect ratio β‐sialon grains homogeneously distributed in an α‐sialon matrix. A number of the larger α‐sialon grains contained dislocations and showed a core/shell structure. Dy gave an α‐sialon which was stable over a wide temperature range (1350–1800°C) for long holding times, while the use of Sm resulted in less stable α‐sialon structures at medium temperatures (1450°C) and the formation of melilite, R 2 Si 3−x Al x O 3+x N 4−x , β‐sialon, and the 21R sialon polytype during prolonged heating. High α‐phase contents gave a very high hardness ( H V10 is approximately 22 GPa) but a comparatively low indentation fracture toughness (around 4.4 MPam 1/2 ). Duplex sialons fabricated from powder mixtures corresponding to an α‐to‐β sialon ratio of around 50:50 resulted in a sialon material with a favorable combination of high hardness (around 22 GPa) and increased toughness (to around 5.5 MPam 1/2 ).