Coloured silicon nitride material - contains transition metal to promote colour homogeneity.

: Herrmann, M.; Schubert, C.; Klemm, H.; Goeb, O.

Abstract
A coloured, sintered or sinterable sintering aid-containing silicon nitride material contains 0.3-10 wt.% silicide-forming transition metals for a black colour and less than 0.3 wt.% d-transition metals for other colours. Preferably, the material has a grey colour or an ivory to white colour respectively when it contains less than 0.15 wt.% or less than 0.05 wt.% silicide-forming transition, other colours being obtained by addition of 2-50 wt.% colouring additives. Also claimed is production of the above silicon nitride material, in which silicon nitride powder, having one of the above d-transition metal contents, is subjected to sintering at normal pressure, pressure sintering or hot pressing. ADVANTAGE - The d-transition metal content promotes uniformity of colouring of the silicon nitride material and allows production of black silicon nitride material with a strength of above 500 MPa.