Oriented crystallisation of lithium niobate containing glass ceramic in an electric field and determination of the crystallographic orientation by infrared spectroscopy

A glass melt with the composition (mol%) 45Li 2 O, 20Nb 2 O 5 and 35SiO 2 was soaked at 1000°C. This did not lead to any crystallisation. A current of 50 mA applied between the platinum crucible (anode) and a platinum wire inserted into the melt (cathode) resulted in a crystallisation of LiNbO 3 , Li 2 Si 2 O 5 and Li 2 SiO 3 at the cathode. The resulting glass ceramic showed textured structures which indicate dentritic growth. The nucleation process caused by current flow is, supposedly an effect of the Nb 4+ formed. This should lead to a decrease in viscosity in the vicinity of the cathode and, therefore, the nucleation is enabled. An orientation of the niobate crystals perpendicular to the electrode also observed in pole figures was shown by means of reflectance spectra and the dielectric function determined after Kramer's Kronig analysis. Infrared reflectance spectroscopy can be used for the qualitative detection of orientation effects.