Optical and luminescence characteristics of Eu³⁺ doped zinc bismuth borate (ZBB) glasses for red emitting device

Abstract Zinc bismuth borate (ZBB) glasses with chemical composition of (60 - x) B₂O₃: 30Bi₂O₃: 10ZnO: xEu₂O₃ for different Eu₂O₃ concentrations of x = 1, 3, 5, 7 and 9 mol% were prepared by the conventional melt quenching technique. The density and molar volume of the glasses have been found to increase with Eu₂O₃ concentration. The IR studies indicated that these glasses were made up of [BiO₃], [BO₃], [BO₄] and [BO] basic structural units. The absorption spectra had revealed two intense bands due to ⁷F₀ → ⁷F₆ (2076 nm) and ⁷F₁ → ⁷F₆ (2198 nm) transitions in the NIR regions. The fractional populations of the (⁷F₀) and (⁷F₁) ground state were 65% and 35%_, respectively. Five luminescence bands were observed at 579 nm (⁵D₀ → ⁷F₀), 589 nm (⁵D₀ → ⁷F₁), 613 nm (⁵D₀ → ⁷F₂), 651 nm (⁵D₀ → ⁷F₃) and 696 nm (⁵D₀ → ⁷F₄), when excited by a 465 nm source, the most intense red emission was found at 613 nm. A shorter decay time of ⁵D₀ excited state was found with increasing of Eu³⁺ concentration as more asymmetries were created around Eu³⁺. For comparison, further investigations were carried out with two other glass structures; bismuth borate glass (BB) and zinc borate glass (ZB), doped with Eu³⁺ in the same range. The ZBB glasses have exhibited with the highest emission intensity especially at 613 nm; the intensity for the ZBB was around 7 times of the ZB and twice of the BB glasses.