An insight into the preferential substitution and structure repair in Eu2+-doped whitlockite-type phosphors based on the combined experimental and theoretical calculations. Issue 29 (8th July 2019)

• Record Type: Journal Article
• Authors: Qiu, Zhongxian; Zhou, Wenli; Ma, Zhongyun; Zhang, Jilin; Lian, Shixun; Liu, Ru-Shi
• Is Part Of: Journal of materials chemistry. Volume 7:Issue 29(2019)
• Page Start: 8954
• Page End: 8961
• Publication Date: 2019-07-08
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9tc01832h
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Due to the wide compositional variability and structural tolerance, Eu 2+ -doped whitlockite β-Ca3 (PO4 )2 (TCP)-type phosphors with different visible emissions have been realized by manipulating the chemical compositions. Abstract : Due to the wide compositional variability and structural tolerance, Eu 2+ -doped whitlockite β-Ca3 (PO4 )2 (TCP)-type phosphors with different visible emissions have been realized by manipulating the chemical compositions. However, the site preference of the dopant Eu 2+ at the multi-cation sites has been a dispute recently. In this study, a combination of experimental and theoretical calculations was applied to identify the preferential occupancy and variable optical behavior of Eu 2+ through the evolution of Ca10.5−0.5 x K x (PO4 )7 (0 ≤ x ≤ 1) isostructures. Both spectral analysis and theoretical calculations reveal that Eu 2+ prefers to occupy the loose Ca(4) sites and produce a narrow band emission around 420 nm. Moreover, a continuous increase in the K content compels the redistribution of dopants from the Ca(4) into the Ca(3) site, resulting in an abrupt spectral shift to 470 nm. Moreover, a vacancy defect repair effect was proposed for the enhancement in the luminescence of Ca10.5−0.5 x K x (PO4 )7 :Eu 2+, in which the incorporation of K + repaired the half-unoccupied Ca(4) sites and benefitted the reduction of Eu 3+ to Eu 2+ . Moreover, to further prove the significant vacancy repair and dopant redistribution effects, Na + - and Li + -doped systems were investigated. In addition, together with the reported Sr 2+ - or Gd 3+ -doped systems, the preferential occupancy and saltatory spectral variations of Eu 2+ in whitlockite-type phosphors were uniformly clarified by cationic modification events.