<i>M</i><sub><i>x</i></sub>La<sub>1–<i>x</i></sub>SiO<sub>2–<i>y</i></sub>N<sub><i>z</i></sub> (<i>M</i> = Ca/Sr/Ba): Elucidating and Tuning the Structure and Eu<sup>2+</sup> Local Environments to Develop Full-Visible Spectrum Phosphors
Mahdi Amachraa, Shuxing Li, Po-Yuan Huang, Ru‐Shi Liu, Zhenbin Wang, Rong‐Jun Xie, Shyue Ping Ong
Abstract
The local environments of rare-earth activators have profound effects on the luminescent properties of phosphors. Here, we elucidate the crystal structure of the LaSiO2N phosphor host using a combination of density functional theory calculations and synchrotron X-ray diffraction. We determine that LaSiO2N crystallizes in the monoclinic C2/c instead of the hexagonal P6̅c2 space group. To improve the luminescence performance, divalent cations M (M = Ca/Sr/Ba) were introduced into LaSiO2N to eliminate Eu3+. A family of apatite M1+xLa4–xSi3O13–x/2:Eu2+ (x ∼ 1.5, M = Ca/Sr/Ba) phosphors was further developed with unprecedented ultra-broadband (290 nm) emission spectra and excellent thermal stability. Detailed local environment investigations reveal that the formation of oxygen vacancies within and beyond the first-shell environment of Eu2+ is responsible for the redshift and broadening of the emission spectra via geometrical alteration of the Eu2+ local environment. This work provides new insights for understanding and optimizing the luminescence of rare-earth phosphors.