Stabilization of Eu2+ in Li2B4O7 with the BO3 network through U6+ co-doping and defect engineering. Issue 3 (21st December 2022)

• Record Type: Journal Article
• Authors: Balhara, Annu; Gupta, Santosh K.; Patra, G. D.; Modak, Brindaban; Prakash, J.; Sudarshan, K.; Mohapatra, M.
• Is Part Of: Physical chemistry chemical physics. Volume 25:Issue 3(2023)
• Page Start: 1889
• Page End: 1902
• Publication Date: 2022-12-21
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d2cp04672e
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : This work demonstrates a unique strategy for stabilizing Eu 2+ ions in Li2 B4 O7 for color-tunable light emission through defect engineering by the virtue of U 6+ co-doping. Abstract : Owing to the unique 4f–5d transitions and the involvement of 5d electrons, the divalent europium (Eu 2+ ) ion is extensively used as a dopant ion in luminescent materials for phosphor-converted light emitting diodes (pc-LEDs) and other technological applications. Earlier reports in most of the cases have shown that the reduction of Eu 3+ to Eu 2+ requires very high temperatures and large hydrogen flux. In this study, a co-doping strategy with higher valent U 6+ ions was utilized to successfully stabilize Eu 2+ ions in the Li2 B4 O7 (LTB) host with both the BO3 and BO4 network in low H2 flux of only 8%. It is postulated that charge transfer occurs from U to Eu, resulting in the reduction of the charged state of Eu and the reaction probably proceeds via the formation of paramagnetic transient [U 5+ –Eu 3+ ] species in the co-doped LTB. The same is also believed to be facilitated by the enhanced formation of Li–O type vacancy clusters in co-doped samples and enhanced oxygen vacancies in a reducing atmosphere. We believe this work will pave a new pathway for stabilizing the unusual oxidation state of lanthanides and transition metal ions through co-doping with hexavalent uranium ions.