Crystal Phase and Morphology Control for Enhanced Luminescence in K₃GaF₆:Er³

Upconversion luminescent materials (UCLMs) have garnered significant attention due to their broad potential applications in fields such as display technology, biological imaging, and optical sensing. However, optimizing crystal phase and morphology remains a challenge. This study systematically investigates the effects of phase transformation and morphology control on the upconversion luminescent properties of K₃GaF₆:Er³⁺. By comparing different synthesis methods, we found that the hydrothermal method effectively facilitated the transformation of the Na_xK_3-xGaF₆ crystal phase from cubic to monoclinic, with Na⁺/K⁺ ions playing a key role in the preparation process. Furthermore, the hydrothermal method significantly optimized the particle morphology, resulting in the formation of uniform octahedral structures. The 657 nm red emission intensity of the monoclinic phase sample doped with Er³⁺ was enhanced by 30 times compared to that of the cubic phase, clearly demonstrating the crucial role of phase transformation in luminescent performance. This study emphasizes the synergistic optimization of crystal phase and morphology through phase engineering, which substantially improves the upconversion luminescence efficiency of K₃GaF₆:Er³⁺, paving the way for further advancements in the design of efficient upconversion materials.