Surface Texture Formation in Al ₂ O ₃ Substrates

Crystallographic texture formed at the surface during the sintering of 3 tape‐cast Al ₂ O ₃ substrates was studied as a function of sintering temperature and atmosphere. The sintering atmosphere strongly influenced the surface texture formed. A strong (001) basal‐plane fiber texture normal to the plane of the substrate is produced when commercial green substrates are sintered in air at 1600° to 1700°C; sintering in vacuum (< 2 × 10 ^‐6 mm Hg) or dry H ₂ produces a weaker texture. Grain growth is a necessary but insufficient condition for the formation of a strong surface texture. It is proposed that surface texture formation is caused by an excess driving force which results in growth of grains with a low‐surface‐energy plane exposed at the substrate surface. Since the surface energy of a crystallographic plane is a function of atmosphere and impurities adsorbed on the surface, both these factors should have a pronounced effect on surface texture formation, as observed in the present study.