EFFECT OF Ti ON THE OPTICAL BAND GAP OF FERROELECTRIC BaTixO5-BASED BULK GLASS

Abstract

Optical transmittance on ferroelectric BaTi x O 5 (x=1.7, 2, 2.1)-based glasses prepared recently by a containerless synthesis technique is measured at room temperature in the wavelength range 190–800 nm. A sharp decrease in the transmittance observed in the ultraviolet (UV) region, which shifts toward longer wavelength region on increasing x is associated with fundamental absorption edge. From the linear region of the absorption coefficient calculated from the transmittance spectrum the optical band gap of 3.41 eV is estimated for x=1.7, which decreases on increasing x. The Urbach energy increases on increasing x demonstrating an increase of structural disorder in the ferroelectric BaTi x O 5 glass on increasing Ti concentration.