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

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.