Thermal exposure of willemite (α-Zn2SiO4) (00•1) surface at 1250C caused a surface pre-melt layer having silica-rich composition, yet with similar structural units as willemite according to energy-dispersive X-ray and reflection infrared spectroscopic analyses. Shallow hexagonal pits nucleated subsequently at dislocation out-crops beneath the surface-premelt layer, as a result of accumulation of inhibitor impurities to maintain undersaturation of etched components at dislocation outcrops, thus allowing etch pits to develop at these high energy sites. Thermal cycling between ambient and the selected

temperature (1250C) caused slight deepening of hexagonal pits with progressively corrugated terrace steps, as well as the formation of hillocks at their centers, in accordance with the inhibition effect of impurities at dislocation out-crops. Polygonization, pore faceting and crack healing also occurred for thermally cycled crystals according to transmission electron microscopy observations.

Thermal Cycle Etching of Willemite (0001) - Effects of Surface Premelting, Dislocation Out-Crops and Polygonization. P.T.Chao, P.Shen, C.C.Lin: Materials Science and Engineering A, 2002, 335[1-2], 191-7