Upconversion Luminescence Properties of Er³⁺ Doped Yb₂Ti₂O₇ Nanophosphor by Gd³⁺ Codoping

Abstract

Er 3+ doped Yb 2 Ti 2 O 7 nanophosphors by Gd 3+ codoping with nominal composition of (Er 0.05 Yb 0.95− x Gd x ) 2 Ti 2 O 7 (x = 0, 0.2, 0.4, 0.6, 0.8, and 0.95) have been prepared by sol–gel method. −Er 3+ –Gd 3+ codoped Yb 2 Ti 2 O 7 was characteristic of a typical face-centered cubic crystal phase, and the unit cell parameter increased linearly with the increase of Gd 3+ concentration. Under a 976 nm laser diode excitation, both green and red upconversion emissions were observed and the upconversion emissions were enhanced significantly by Gd 3+ codoping, showing the strongest green and red emissions at 80 mol% Gd 3+ codoping. The intensity ratio of green to red emissions (Igreen/Ired) increased monotonously with the increase of Gd 3+ concentration. The energy transfer between Yb 3+ and Er 3+ and the variation of local crystal field symmetry of Er 3+ by the substitution of Yb 3+ by Gd 3+ ions led to the improvement of upconversion properties of Er 3+ –Gd 3+ codoped Yb 2 Ti 2 O 7 nanophosphors.