Synthesis and study of luminescence properties of a deep red-emitting phosphor K2 LiAlF6 :Mn4+ for plant cultivation.

Abstract

Light is the most important component in plant growth and development. This study synthesised a novel Mn4+ -doped K2 LiAlF6 red-emitting phosphor using the coprecipitation method. We observed that on addition of dopant Mn4+ ions to the host K2 LiAlF6 , its phase changed from rhombohedral to cubic due to the change in the lattice position of the atoms. When the atoms are excited at 468 nm, the K2 LiAlF6 :Mn4+ phosphor exhibited a red emission band ranging from 630 to 700 nm, centred at 638 nm, which matched well with the absorption spectra of phytochrome PR. The critical quenching content of Mn4+ ions was ~3mol%. The critical distance between Mn4+ ions was determined to be 19.724 Å, and non-radiative energy transfer among the nearest-neighbour Mn4+ ions was the mechanism used for the concentration quenching effect. The Commission International de l'Eclairage (CIE) chromaticity coordinates of the K2 LiAlF6 :0.03 Mn4+ sample were (x = 0.7162, y = 0.2837). The luminescence mean decay time was calculated to be 8.29 ms. These results demonstrated the promising prospect of K2 LiAlF6 :Mn4+ as a red-emitting phosphor for application in red light-emitting diodes for plant cultivation.