Oriented lithium disilicate glass–ceramics prepared by electrochemically induced nucleation

Glasses with the compositions Li₂Si₂O₅ and 9Li₂Si₂O₅ · BaSiO₃ were crystallized using electrochemically induced nucleation. A platinum wire was inserted into the melt. A dc-current was supplied between the platinum wire (cathode) and the crucible (anode) at various temperatures below the liquidus temperature. This led to nucleation at the cathode and subsequently to radial growth of lithium disilicate crystals. The crystals exhibit dendritic growth. The main crystal growth direction is the crystallographic c-axis of lithium disilicate. This axis is oriented perpendicular to the electrode surface. A crystal growth selection near the cathode results in a highly textured glass–ceramics. The electrochemically induced nucleation is based on the reduction of the silicate glass to elementary silicon and an alloy formation between Si and Pt with a depletion of Si in the melt near the cathode. The crystalline products were characterized and the effects of experimental parameters were studied.