Abstract: Nitrogen-containing rare earth melilite solid solutions R₂Si_3-xAl_xO_3+xN_4-x(R=Nd,Dy, x=0, 0.3, 0.6, 1.0, R=Yb, x=0, 0.3) were prepared at the temperatures
ranged from 1500℃ to 1750℃ for 2h by pressureless sintering　technique. The reaction sequences of these compositions at the sintering temperatures
were studied. The results showed that nitrogen-containing rare earth (from Nd to Yb) melilite or its solid　solutions can be formed and their amounts in the sintered samples increase with increasing
the temperatures. However, the formation abilities of melilite solid solutions　become weak with decreasing the ionic radii of rare earth elements, i.e. light rare earth melilite solid solutions can be formed as a major phase
at the temperature as low as 1500℃, however, for midium and heavy　rare earth it needs to increase the temperature to 1700℃ and 1750℃
respectively. The other phases to occur in the sintered samples and the factors to affect the formation behaviour of melilite solid solutions were also discussed in the paper.

Key words: rare earth, melilite, reaction behaviour