Key chemical parameters related to the width of the charge transfer band and the emission intensity of 5D0 → 7F2 in Eu3+ doped Ln2O3

• Two key chemical parameters related to photoluminescence properties of Eu3+ were found.
• The relationship between the red emission intensity of Eu3+ and the EFSD was proposed.
• The influence of the environmental factor on the FWHM of O2−–Eu3+ charge transfer was discussed.

The dependences of crystal structure on the width of the O2−–Eu3+ charge transfer (CT) band from the ligands O to the centre ion Eu3+ and the intensity of 5D0 → 7F2 red emission of Eu3+ in Eu3+ doped Ln2O3 (Ln = Y, Gd and Lu) have been discussed. The standard deviation of environmental factor of the individual bond (EFSD), which can be expressed as σ(heμ)=1N∑i=1Nheμ-δ2 (where heμ=(fcμαbμ)1/2QBμ and δ=1N∑i=1Nheμ), was proposed to quantitatively express the distortion degree of LnO6 polyhedron from that of an ideal octahedron. The photoluminescence intensity of 5D0 → 7F2 red emission of Eu3+ increases with increasing of σ(heμ). The environmental factors he=∑μfcμαbμQBμ21/2 of the Eu3+ occupying the site Ln2 were calculated based on the dielectric theory of the complex crystal. The FWHM (the full width at half maximum) of O2−–Eu3+ CT band increases with increasing of he. Therefore, it can increase the intensity of 5D0 → 7F2 red emission of Eu3+ and the FWHM of O2−–Eu3+ CT band through increasing σ(heμ) and he values, respectively. It provides a way to adjust the intensity of Eu3+ red emission and the width of the O–Eu CT band in Eu3+ doped materials.