Luminescent properties of Sm3+ activated β-NaYF4 microcrystals

Sm3+ (1, 3, 5, 7 and 10 at.%) activated β-NaYF4 microphosphors were prepared via hydrothermal process at 200 0C. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) have been used to investigate the morphology and crystal structure of the samples. One interesting outcome of photoluminescence study involved the relative intensity variation of the strongest emission peak at ∼600 nm due to 4G5/2−6H7/2 transition under the excitation of 400 nm. These results were explained on the basis of multiple energy levels and self concentration quenching associated with the activator ion.