The solidification behaviour of melts in the system Zn2SiO4-Mg2SiO4

The melting and solidification behaviour of various compositions across the system Zn₂SiO₄- Mg₂SiO₄ (willemite-forsterite) was studied by means of photoemission electron microscopy, X-ray diffraction and DTA. The results revealed the peritectic type of the phase system instead of the earlier assumed eutectic one. During the formation of willemite solid solutions by rapid solidification of zinc-silicate-rich melts, grain-boundary enrichment of zinc oxide besides magnesium silicate takes place. From melts richer in magnesium silicate, forsterite solid solution forms primarily. The sluggish process of its peritectic decomposition during cooling and the preferred subsolidus formation of zinc silicate give rise to the formation of a ternary non-equilibrium phase assemblage even at slow cooling.