STUDY ON THE SOLID SOLUBILITY OF AL IN THE MELILITE SYSTEMS R(2)SI(3-X)AL(X)O(3+X)N(4-X) WITH R=ND, SM, GD, DY AND Y

The solubility of aluminium the nitrogen-containing melilite structure has been studied by preparation of specimens of the general formula R(2)Si(3-x)Al(x)O(3+x)N(4-x) with R = Nd, Sm, Gd, Dy and Y by hot pressing and pressureless sintering techniques in the temperature interval 1600-1750 degrees C. For elements with large ionic radii, i.e. R = Nd and Sm, up to one Si can be replaced by Al, but the solubility limits in melilite solid solutions decrease with decreasing the ionic radii. Consequently, yttrium-melilite had the lowest obser ved aluminium solubility (x approximate to 0.6) in rare earth elements-melilite solid solutions.