Irregular Fourfold Hierarchy in Fresnoite Dendrites Grown via Electrochemically Induced Nucleation of a Ba₂TiSi_2.75O_9.5 Glass

Abstract

Dendritic growth of fresnoite, a barium titanium silicate, is achieved at 1200 °C from a glass with the composition Ba 2 TiSi 2.75 O 9.5 using electrochemically induced nucleation. The highly oriented main trunk is formed with primary and secondary branches which obey this rule. In between the branches, a fourth hierarchy is built with fine, irregular honeycomb and lamellar structures. A glassy phase occurs between these structures. The crystal orientation is the same in the crystals following the main crystallographic axes as well as the irregular structures. This was proven by determining crystal orientations via electron backscatter diffraction (EBSD). The crystallization of fresnoite at high temperatures was triggered by attaching a dc-potential of a few volts between a platinum crucible containing the melt and a platinum wire inserted into the melt. After a short time crystals were formed at the cathode and grew toward the crucible in the direction of the crystallographic c -axis.