Successful Nd³⁺ Doping of Li₂O–B₂O₃–Al₂O₃ Vitreous System: Optical Characterization and Judd–Ofelt Spectroscopic Calculations

Abstract

This study reports on the synthesis and the physical characterization of a ternary boron-rich (B-rich) lithium–boron–aluminum (LBA: Li₂O–B₂O₃–Al₂O₃) vitreous system successfully doped with increasing Nd₂O₃ content (xNd₂O₃:LBA) in the range 0 ≤ x ≤ 5 wt %. The as-produced samples were investigated using optical absorption, photoluminescence emission, Raman spectroscopy, and differential thermal analysis. The Judd–Ofelt (JO) theory was used to assess the intensity parameters (Ω _λ ), transition probabilities (A(J, J')), branch ratios (β), emission cross-sections (σ), quantum efficiencies (Y), experimental (τ _exp ) and calculated (τ _rad ) radiative lifetimes, and the spectroscopic quality values (χ = Ω ₄/Ω ₆) as a function of the nominal Nd₂O₃ doping content. Over the range of our investigation (0 ≤ x ≤ 5 wt %), we found that the Ω ₂ and Ω ₆JO parameters monotonically increased from 0.17 to 1.26 × 10⁻²⁰ and from 1.19 to 1.84 × 10⁻²⁰, respectively. In contrast, over the same range of nominal Nd₂O₃ doping content we found that the Ω ₄ JO parameter decreased monotonically from 4.12 to 2.05 × 1 0⁻²⁰. Although the τ _exp values increased at the low end of nominal Nd₂O₃ content (up to 2.5 wt %), nonradiative energy transfer mechanisms (e.g., energy migration, cross-relaxation, and losses from networked phonons and O–H vibrational modes) governed the process at the high end of the nominal Nd₂O₃ content. A competition mechanism was proposed to explain the observed behavior in the ⁴F_3/2 ⟶ ⁴I_J’transition lifetime for hosted Nd³⁺ ions.