Macroscopic glass-permeated single-crystals of fresnoite

Abstract

Macroscopic glass-permeated single-crystals of fresnoite (Ba₂TiSi₂O₈, BTS) are grown by a Czochralski-like procedure initiated by electrochemically induced nucleation (EiN). The morphological and crystallographic properties of these materials are analyzed using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) before and after annealing at 1150 °C for 21 h. While continuous orientation changes of 8° mm⁻¹ are observed in dendritic single crystals competing with others during growth, only changes of 0.2° mm⁻¹ are observed in a freely grown dendrite over an area of more than 1 cm². A type of intragranular Ostwald ripening and the formation of the high temperature phase of BaSi₂O₅ occur during annealing. Two phase separated residual glasses are observed between the crystals.