First observation of mutual energy transfer of Mn4+–Er3+via different excitation in Gd2ZnTiO6:Mn4+/Er3+ phosphors

Abstract

Mutual energy transfer between rare earth ions and transition metal ions in a single luminescence material easily achieves multifunctions by altering the excitation wavelength. In this study, we first observe the mutual energy transfer process between Mn⁴⁺ and Er³⁺via different excitations in Mn⁴⁺–Er³⁺ co-doped Gd₂ZnTiO₆ phosphors synthesized by a high temperature solid-state reaction. During the downshift energy transfer from Mn⁴⁺ to Er³⁺, the Gd₂ZnTiO₆:Mn⁴⁺/Er³⁺ phosphor exhibits a strong near-infrared emission around 1529 nm with a wide excitation band extending from 250 to 550 nm. Based on Dexter's theory, the energy transfer mechanism mainly contributes to a dipole–dipole interaction between Mn⁴⁺ and Er³⁺ ions, which is responsible for the greatly enhanced emission at 1529 nm. Upon the upconversion energy transfer from Er³⁺ to Mn⁴⁺, the Gd₂ZnTiO₆:Mn⁴⁺/Er³⁺ phosphor shows a deep red emission of Mn⁴⁺ under 980 nm laser excitation. The energy transfer process from Er³⁺ to Mn⁴⁺ is fully demonstrated by variations in excitation power as well as luminescence lifetimes of 551 nm emission of Er³⁺. Two-photon processes and resonance energy transfer from Er³⁺ to Mn⁴⁺ are required to populate the ²E emitting level of Mn⁴⁺.