First-principles study of luminescence properties of the Eu-doped defect pyrochlore oxide KNbWO6 ⋅ H2O : 0.125 Eu3

• Published in: Physical review. B 2020-07, Vol.102 (3), p.1
• Main Authors: Choe, Song-Hyok, Yu, Chol-Jun, Choe, Myong, Kye, Yun-Hyok, Han, Yong-Nam, Pang, Guangsheng
• Format: Article
• Language: English
• Subjects: Conduction electrons; Defects; Dipoles; Energy transfer; Europium; First principles; Hole mobility; Incident light; Luminescence; Optical properties; Symmetry; Water chemistry
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.102.035131

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 KNbWO6 : 0.125 Ln3+ 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 Eu3+ ion and the band structure with an alteration of their luminescent behavior. In the hydrated compounds, the electric-dipole 5D0 − 7F2 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 Eu3+ ions and the host. It turns out that the oxygen vacancies are detrimental to luminescence as they reduce the Eu3+ ion in its vicinity to the Eu2+ ion and also serve as traps for conduction electrons excited by incident light. Our calculations for KNbWO6 : 0.125 Ln3+ (Ln=Ce, Pr, Nd, Pm, Sm) support that the defect pyrochlore oxide KNbWO6 can also be used as a luminescence host for Ln3+ ion doping, giving valuable insight into a variation trend in luminescent properties of these materials at the atomic level.