Fluorides have drawn tremendous attraction as a class of host matrix for rare-earth (RE) ions over other classes of materials such as oxides, phosphides, and nitrides, etc., due to their high optical transparency in UV-vis-IR regions, high refractive index, and thermal and chemical stabilities. The RE-doped alkali/alkaline metal fluorides have a wide range of applications including biological sensor, optical sensor, and scintillation. However, there is limited research on the Cs2HfF6 matrix. Herein, we report the luminescence characteristics of Eu3+ and Tb3+ singly or codoped Cs2HfF6 materials, by replacing Hf synthesized via co-precipitation method. The concentrations of dopant ions were varied and further optimized to understand the role of the Tb3+ ion as a sensitizer to enhance the red emission of the Eu3+ ion. Morphology of the as prepared particles was close to spherical shape with uniform size distribution as observed in scanning electron microscopy. The X-ray diffraction (XRD) patterns revealed the formation of pure hexagonal Cs2HfF6 with no impurity or secondary phase even with 50% doped samples. Photoluminescence (PL) study of Tb3+- and Eu3+-codoped samples revealed the tunable emissions based on dopant concentration where Tb3+ ion assist for energy transfer phenomena. The singly doped and codoped samples were further studied via cathodoluminescence (CL) under high energy radiation. The CL emission spectra were in good agreement with the energy transfer mechanism as observed in the PL study.

Photoluminescence and cathodoluminescence of rare-earth doped fluoride Cs2HfF6

ACS Spring 2022

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