Tunable upconversion luminescence and energy transfer process between Yb3+ and Er3+ in the CaY4F14

Yb3+/Er3+ codoped CaY4F14 materials with tunable upconversion (UC) emission were prepared by a high temperature solid-state method. Based on the UC luminescence properties investigations, it was found that, under 980 nm excitation, CaY4F14:Yb3+,Er3+ showed green–yellow–red upconversion luminescence by changing the composition of the Yb3+-Er3+ dopants. It was also found that the green and red emissions originated from the two photon processes, and the ground-state absorption (GSA), excited-state absorption (ESA) and energy transfer (ET) processes between Er3+/Yb3+ ions were involved in the upconverted emission mechanism. The measured lifetimes show a strong dependence on Yb concentration.