Near-IR emission enhancement of K₂LuF₅: Yb³⁺/Er³⁺ via the cross-relaxation processes with the assistance of Ce³⁺ ions

Yb³⁺/Er³⁺ co-doped K₂LuF₅ micro-crystals have been synthesized via a facile and environmentally-friendly hydrothermal route. The effects of Ce³⁺ on the upconversion (UC) and downconversion (DC) luminescence properties of K₂LuF₅: 16%Yb³⁺, 2%Er³⁺ under the excitation of 980 nm laser diode (LD) are systematically investigated. The emission intensity located at 1.54 μm of 15 mol% Ce³⁺ doped sample is enhanced about 6 times, in comparison with that of Ce³⁺-free sample. It is proposed that the efficient cross-relaxation processes between Er³⁺ and Ce³⁺ ions contribute to the competition between UC and DC transitions, and the success in varying the UC and DC radiation rate. In addition, with an increasing of excitation power density, the cross-relaxation process of Ce³⁺ ions doped samples is promoted, which leads to a multicolor output. This study could be expected to promote the development of Ce³⁺ doped K₂LuF₅: 16%Yb³⁺, 2%Er³⁺ as micro-optical device.