Controlled synthesis and photoluminescence properties of hexagonal Eu3+ activated Na(Y,Gd)F4 microphosphors

Abstract

Rare earth (RE) doped upconversion materials capable of turning the incident NIR photons into UV–vis photons have shown promising potentials in the fields of solar cells [1], sensors [2], and so on. The efficient upconversion materials are based on fluorides specially NaYF4, which are codoped with rare earth (RE) ions. These are generally exhibit multicolor fluorescence emission from ultraviolet to infrared (IR) because of the abundance of the 4fN electronic states of the RE ions. Therefore, different technologies have been explored to obtain and tune fluorescence emission, which remains a considerable challenge for researchers. In this work, a series of hexagonal phase of sodium fluorides microcrystals have been successfully synthesized through controlled hydrothermal methods. The rietveld refinement of XRD and TEM SAED pattern has been employed to investigate the structure and morphology. Formation of single phase hexagonal microcrystals is detected for all the doping concentrations. Raman and FTIR spectra show the functional group and vibrational modes present in the system. We would expect in such phosphors, mutual correlations and competitions among the lanthanides especially in this fluoride tuned the luminescent properties of the host. The current study suggests that the sodium fluorides microcrystals with the strong red emission may have great potential applications in micro-fiber laser, multicolor display etc.