Electrochemical nucleation for the preparation of oriented glass ceramics

Abstract During cooling of a glass melt with the composition of 2BaO · TiO 2 · 2.75SiO 2 crystallization takes place at 1030°C during DTA measurements and at 1220°C, if the glass melt is placed in a rotation viscosimeter. If higher temperatures are used, e.g., 1300°C, a cathodic current flow of 45 mA/cm 2 is achieved by attaching a dc-potential of 1.2 V and crystallization of fresnoite takes place at the cathode, leading to a highly oriented structure. The crystallites show fast dendritic growth and the crystallographic c -axis is oriented perpendicular to the electrode surface. Electrochemically induced nucleation runs parallel with the reduction of Ti 4+ of Ti 3+ which is supposed to decrease the viscosity, increase the diffusion coefficient and possibly alter the surface tension of the nuclei formed.