Influence of titanium redox states on luminescence and conductivity in TiO2 -doped borophosphate glass system

Abstract

Borophosphate glasses have garnered significant interest due to their potential for optical and electronic applications. This research delves into the luminescent and conductive properties of 40P₂O₅–25B₂O₃-(35-x) BaO-xTiO₂ (x = 0–5 mol%) glasses synthesized via the melt-quench method. The glass doped with 4 mol% TiO₂ exhibited intense luminescence within the 400–600 nm spectrum, manifesting as a vivid blue emission and the highest Ti³⁺ ion concentration. Beyond this threshold, the luminescence intensity waned, highlighting the significance of Ti⁴⁺/Ti³⁺ ratios. Absorption spectra and X-ray photoelectron spectroscopy were utilized to study these multivalent ions. Temperature-dependent AC conductivity, exhibited a linear increase, consistent with the Correlated Barrier Hopping (CBH) model. Enhanced polaron hopping between Ti³⁺ and Ti⁴⁺ with increasing TiO₂ content improved the dielectric constant and conductivity, peaking at 4.145×10⁻⁵ Scm⁻¹ at 5 mol% TiO₂ within the 450–530 °C range. These findings underscore the tunability of TiO₂-doped glasses for optoelectronic applications.