First-principles study of luminescence properties of the Eu-doped defect pyrochlore oxide KNbWO6·H2O:0.125Eu3+
Year: 2020
Type: article
Abstract: Defect pyrochlore oxides have attracted great interest as a promising luminescent material due to their flexible composition and high electron/hole mobility. In this paper, we investigate the structural and electronic properties of lanthanide-doped (Ln) defect pyrochlore oxides ${\mathrm{KNbWO}}_{6}:0.125{\mathrm{Ln}}^{3+}$ by using first-principles calculations. We perform structural optimizations of various defect pyrochlore models and calculate their electronic structures, revealing that hydration has a significant influence on both the local symmetry around the ${\mathrm{Eu}}^{3+}$ ion and the band structure with an alteration of their luminescent behavior. In the hydrated compounds, the electric-dipole $^{5}D_{0}\text{\ensuremath{-}}^{7}F_{2}$ transition is found to be partially suppressed by a raised local symmetry, and the water molecules in the compounds can mediate the nonradiative energy transfer between the activator ${\mathrm{Eu}}^{3+}$ ions and the host. It turns out that the oxygen vacancies are detrimental to luminescence as they reduce the ${\mathrm{Eu}}^{3+}$ ion in its vicinity to the ${\mathrm{Eu}}^{2+}$ ion and also serve as traps for conduction electrons excited by incident light. Our calculations for ${\mathrm{KNbWO}}_{6}:0.125{\mathrm{Ln}}^{3+}$ (Ln=Ce, Pr, Nd, Pm, Sm) support that the defect pyrochlore oxide ${\mathrm{KNbWO}}_{6}$ can also be used as a luminescence host for ${\mathrm{Ln}}^{3+}$ ion doping, giving valuable insight into a variation trend in luminescent properties of these materials at the atomic level.
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funder: State Committee of Science
OpenAlex ID: W3000411047