Evolution of different defect clusters in Eu3+ doped KMgF3 and Eu3+, Li+ co-doped KMgF3 compounds and the immediate impact on the phosphor characteristics. Issue 21 (30th April 2020)

• Record Type: Journal Article
• Authors: Pathak, Nimai; Mukherjee, Sumanta; Das, Debarati; Dutta, Dhanadeep; Dash, Smruti; Kadam, Ramakant Mahadeo
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 21(2020)
• Page Start: 7149
• Page End: 7161
• Publication Date: 2020-04-30
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0tc00146e
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Different type of defect clusters were found to exist in Eu 3+ :KMgF3 and Li +, Eu 3+ :KMgF3 compounds, which can change the surrounding local structure of Eu 3+ dopant ion. This resulted in different emission characteristics of Eu 3+ ions, which can change the phosphor characteristics of the compounds. Abstract : Defects in the lattice have both positive and negative implications for the optical properties of light emitting materials and a great effort is required to understand the defect structure surrounding the activator ion in phosphor materials. The fluoride based perovskite class of compounds such as KMgF3 is always associated with cationic and anionic vacancies, which may give rise to many interesting optical properties. They may also play an important role in determining the phosphor characteristics, when an activator such as Eu 3+ ions is doped in KMgF3 . This is because defects may alter the local structure of Eu 3+ ions, whose characteristic transitions are very sensitive to the local environment. In the first attempt of its kind, we have tried to present a complete picture of the defect structures both in undoped and Li +, Eu 3+ ion doped KMgF3 compounds and their influence on the phosphor characteristics. By analysing the changes in the defect structure due to changes in the dopant ions using positron annihilation lifetime spectroscopy supported by EPR and theoretical calculations, it was observed that different defect clusters are being evolved upon changing the dopant ions from Eu 3+ to Li + as co-dopant ions. These changes have a direct impact on the emission characteristics, especially the colour can be tuned to a more deep red region. Using time resolved spectroscopy two different Eu 3+ components adjacent to different defect clusters are isolated. The clusters due to K-vacancies were found to change their configuration upon co-doping Li + ions; VC1 for Eu 3+ doped and VC2 for Eu 3+ and Li + co-doped compounds. From the relative percentage of these cluster vacancies, it was possible to make a conclusion about the distribution of Eu 3+ and Li + ions among the different unit cells of KMgF3, which have different defect structures. The study will be helpful in tailoring the defect structure while designing an efficient phosphor material.