Abstract
Dense ceramics with overall compositions DyxSi12-4.5xAl4.5xO1.5xN16-1.5x, where 0.2≤x≤1.0, along the Si3N4–Dy2O3·9AlN tie line were prepared by hot-pressing at 1800°C. The dysprosium-doped α-sialon phase formed in the composition range 0.3≤x≤0.7. Sintered materials of different compositions were post-heat-treated at temperatures in the range 1300–1750° C for different times and it was shown that the Dy-α-sialon phase is stable over a large temperature interval and during heat treatment times up to 30 days. Unlike corresponding neodymium- and samarium-doped α-sialons, dysprosium-doped α-sialon does not decompose into β-sialon and rare-earth-rich grain-boundary phase(s) at temperatures below 1550°C. The α-phase can coexist with a liquid phase at temperatures ≥1550°C and with the Dy-M′-phase (Dy2Si3-xAlxO3+xN4-x) at lower temperatures. When heat treated at 1450°C, any residual liquid grain-boundary phase reacted with minor amounts of the α-sialon phase and devitrified to Dy-M′-phase, yielding a glassy phase-free material. The Dy-M′-phase formed had the maximum aluminium substitution, i.e. x≈0.7. Dysprosium-doped α-sialon exhibited very high hardness (Hv10=22 GPa) and a fracture toughness of 4.5 MPa m1/2, and the hardness and toughness decreased only slightly after devitrification of the glassy phase. Some elongated α-sialon grains were formed at high x values in glassy phase-containing materials, but their presence did not affect the toughness significantly.
Similar content being viewed by others
References
K. H. Jack, in NATO ASI Series “Progress in Nurogen Ceramics”, edited by F.L. Riley (Martinus Nijhoff, 1983) p. 45.
G. Z. Cao and R. Metselaar, Chem. Mater. 3 (1991) 242.
T. EkstrÖm and M. Nygren, J. Am. Ceram. Soc. 75 (1992) 259.
T. EkstrÖm, Mater. Res. Soc. Symp. Proc. 287 (1992) 121.
T. EkstrÖm, Mater. Forum 17 (1993) 67.
S. Hampshire, H. K. Park, D. P. Thompson and K H. Jack, Nature(Lond.) 274 (1978) 880.
Z. K. Huang, T. Y. Tien and T. S. Yen, J. Am. Ceram. Soc. 69 (1986) C–241.
W. Y. Sun, T. Y. Tien and T.-S. Yen, ibid. 74 (1991) 2547.
H. Mandal, D. P. Thompson and T. EkstrÖm, J. Eur. Ceram. Soc. 12 (1993) 421.
T. EkstrÖm and Z. J. Shen, in “5th International Symposium on Ceramic Materials and Components for Engine”, edited by D. S. Yan, X. R. Fu and S. X. Shi (World Scientific, Singapore, 1995) p. 206.
Z. J. Shen, T. EkstrÖm and M. Nygren, J. Eur. Ceram. Soc., 16 (1993) 43.
Idem, J. Am Ceram Soc., 79(3) (1996) 721.
Idem, J. Hard Mater., 29 (1996) 893.
G. R. Anstis, P. Chantikul, B. R. Lawn and D. P. Marshall, J. Am. Ceram. Soc. 64 (1981) 533.
K.-E. Johansson, T. Palm and P.-E. Werner, J. Phys. E13 (1980) 1289.
P.-E. Werner, Arkiv Kemi 31 (1969) 513.
T. EkstrÖm, P.-O. KÄll, M. Nygren and P.-O. Olsson, J. Mater. Sci. 24 (1989) 1853.
P. L. Wang, H. Y. Tu, W. Y. Sun, D. S. Yan, M. Nygren and T. EkstrÖm, J. Eur. Ceram. Soc., 15 (1995) 689.
L.-O. Nordberg, Z. J. Shen and T. EkstrÖm, J. Eur. ceram. Soc., 15 (1995) in press.
T. EkstrÖm, J. Hard Mater. 4 (1993) 77.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
SHEN, Z., EKSTROM, T. & NYGREN, M. Preparation and properties of stable dysprosium-doped α-sialon ceramics. Journal of Materials Science 32, 1325–1332 (1997). https://doi.org/10.1023/A:1018512824740
Published:
Issue Date:
DOI: https://doi.org/10.1023/A:1018512824740