Oriented glass-ceramics containing fresnoite prepared by electrochemical nucleation of a BaO–TiO2–SiO2–B2O3 melt

Glasses with the composition of 2BaO·TiO2·2SiO2·xB2O3 were melted. A platinum wire was inserted into the melt and at 1220°C a dc-current of 10 mA was supplied between the wire (cathode) and the crucible (anode). This led to a crystallization of fresnoite (Ba2TiSi2O8) at the cathode. The crystallization front proceeded to the crucible wall. The result was a highly aligned structure. The crystallographic c-axis of the fresnoite was oriented perpendicularly to the electrode surface. These glass-ceramics are mechanically stable and can easily be cut, ground and polished, which is in contrast to those which do not contain boron oxide.