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α′-Sialon ceramics

Naturevolume 274pages880882 (1978) | Download Citation



OUR previous report1 on Si–Al–O–N ceramics stated that expanded α-silicon ‘nitride’ structures had been obtained by reaction of lithium–silicon nitride, LiSi2N3, with alumina. The unit-cell dimensions of one example (a, 7.822; c, 5.677Å) gave a cell volume about 3% greater than that of α-silicon nitride. Subsequent work2 showed a variation in dimensions for the α′-lithium sialon when lithium aluminate, LiAlO2, was reacted in different proportions with Si3N4. However, other phases, such as β′-sialon and nitrogen–eucryptite, were always present and the product never contained more than 30% of the α′ material. αν-Sialons were also found in the Mg–Si–Al–O–N system3 but again never pure, and were observed by Masaki et al.4 during the nitriding of silicon with A1N and A12O3 additions. A recent claim by Mitomo5 of α′ solid solutions of Si3N4–Al2O3 and/or Si3N4–Y2O3 occurring during the sintering of Si3N4 at 1,700–1,800 °C with Al2O3–Y2O3 mixtures prompted this report of the preparation and characterisation of pure α′-phases in M–Si–Al–O–N systems where M is Li, Ca or Y. Such phases also occur, but have not so far been prepared in a pure form, in magnesium and other sialon systems.

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  1. 1

    Jack, K. H. & Wilson, W. I. Nature phys. Sci. 238, 28 (1972).

  2. 2

    Jama, S. A. B., Thompson, D. P. & Jack, K. H. Special Ceramics 6 (ed. Popper, P.) 299 (BCRA, Stoke-on-Trent, 1975).

  3. 3

    Jack, K. H. J. materials Sci. 11, 1135 (1976).

  4. 4

    Masaki, H., Oyama, Y. & Kamigaito, O. Jap. J. appl. Phys. 14, 301 (1975).

  5. 5

    Mitomo, M. Yogyo-Kyokai-Shi 85, 50 (1977).

  6. 6

    Wild, S., Grieveson, P. & Jack, K. H. Special Ceramics 5 (ed. Popper, P.) 385 (BCRA, Stoke-on-Trent, 1972).

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  1. Wolfson Research Group for High-Strength Materials, Crystallography Laboratory, The University, Newcastle upon Tyne, UK

    • , H. K. PARK
    • , D. P. THOMPSON
    •  & K. H. JACK


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