Upconversion Luminescence of Tb3+ and Yb3+ Co-doped Hexagonal and Monoclinic GdPO4 Nanophosphors

Abstract

Tb3+ and Yb3+ codoped hexagonal GdPO4 nanorods have been prepared by a hydrothermal method at 220°C for 12 h and monoclinic GdPO4 nanoparticles have been obtained by sintering the hydrothermal products at 900°C for 5 h. Green upconversion luminescence of Tb3+ has been observed when pumped by 980 nm diodes due to efficiently cooperative energy transfer from codopant Yb3+. The luminescence of Tb3+ in both hexagonal and monoclinic GdPO4 nanophosphors has been comparatively studied. The dependence of the upconversion luminescence intensity on pump laser power shows that two-phonon processes involved in upconversion luminescence of the emission level 5D4 of Tb3+ is populated via two-photon process. Upconversion luminescence emission intensity and the energy transfer efficiency ηT from Yb3+ to Tb3+ ions upon the concentration of Tb3+ have been investigated.