Preparation and investigation on down-conversion near infrared emission of Tb³⁺, Yb³⁺ co-doped Y₂O₃ transparent ceramics

Tb³⁺, Yb³⁺ codoped Y₂O₃ (mole fraction x=0.02, 0.05, 0.1) transparent ceramics of high transparency have been prepared by vacuum sintering and the down-conversion near infrared (NIR) emission has been demonstrated upon a 484 nm excitation. The dominant energy transfer mechanism is the cooperative down-conversion from ⁵D₄ level of one Tb³⁺ ion to the ²F_5/2 level of two Yb³⁺ ions. The suppression of Tb⁴⁺ during vacuum sintering and the suppression of Yb²⁺ due to the nature of Y₂O₃ lattice, together with the large energy gap between Tb³⁺:⁵D₄ level and Tb⁴⁺-Yb²⁺ charge transfer state (CTS) and the low phonon energy of Y₂O₃ make the non-radiative influence from the CTS negligible. In addition, the contribution of Tb³⁺:⁵D₄ → one Yb³⁺:²F_5/2 (non-radiative) → Yb³⁺:²F_7/2 (radiative) process to NIR emission should be little due to the large energy gap between Tb³⁺:⁵D₄ level and low phonon energy of Y₂O₃.