Phase-formation and luminescence properties of Eu³⁺-doped Bi₂O₃ on synthetic process

This work developed a new method to modify the phase formation, morphological characteristics and photoenergy conversion of Eu3+-doped bismuth oxides via solvothermal preparation and post-annealing treatments. As-prepared products are the tetragonal-structured Bi/t-Bi2O2.75:Eu3+ nanocomposites via introducing metallic Bi-0 by in-situ reduction, which showed a ball-like profile (100 nm). After the post-annealing treatments, asprepared Bi/t-Bi2O2.75:Eu3+ developed into cubic phase crystals of Eu3+-stabilized delta-Bi2O3 (delta-Bi2O3:Eu3+), which had a plate-like shape with the length and width of 1-2 mu m. The dark colored Bi/t-Bi2O2.75:Eu3+ shows a very broad absorption band from UV to 735 nm. The post-annealed delta-Bi2O3:Eu3+ shows a yellow nature color and an abrupt cut-off of absorption edge around 570 nm. The investigations focused on different photo-energy conversion modes of two samples, i.e., photoluminescence and photocatalysis. The photo-degradation abilities on RhB solutions were evaluated with the excitation of visible light. As-prepared Bi/t-Bi2O2.75:Eu3+ showed much more excellent photocatalytic behaviors than the post-annealed delta-Bi2O3:Eu3+. Compared with pure delta-Bi2O3, delta-Bi2O3:Eu3+ has comparable photocatalytic ability. The post-annealed delta-Bi2O3:Eu3+ shows very efficient red-luminescence with preferable excitation of near UV-light. The photo-energy conversion mechanisms were proposed to discuss the luminescence properties, decay lifetimes and multivalent ions. Eu3+-doped Bi2O3 could be a good candidate with multimodal photo-energy conversion applications, i.e., photocatalyst and phosphor, depending on the reductant in the synthesis and post-annealing treatment.