Excited States of 3d3 Electrons in K2SiF6:Mn4+ Red Phosphor Studied by Photoluminescence Excitation Spectroscopy

This paper reports on a study of the photoluminescence excitation (PLE) spectra of Mn4+-activated K2SiF6 phosphor at 20 and 300 K. Measurements of the PLE spectra show that the sharp red emissions (2Eg →4A2g) at ∼630 nm are most efficiently excited by irradiation into the spin-allowed transitions 4A2g →4T2g (∼460 nm) and 4A2g →4T1g (∼360 nm). The first efficient excitation band 4A2g →4T2g is structureless at 300 K but shows a sharp origin and some oscillatory peaks at 20 K. A Fourier transform technique is used for analyzing such oscillatory peaks. The second excitation band 4A2g →4T1g shows a structureless shape even at a low temperature (20 K). The third excitation band with a peak at ∼250 nm is very weak and could be assigned as the 4A2g →4T1g transition. The direct excitation of the 2Eg state is also found to produce the sharp red emissions at ∼630 nm with a negligibly small offset in the configurational coordination. The Franck–Condon analysis makes it possible to accurately determine the zero-phonon line energies in the 3d3 electron transitions of the MnF6 2- octahedron.