The synthesis and component of red phosphor, Sr4Al14O25:Mn, were optimized for application in white light-emitting diodes. The microstructure and morphology were investigated by the X-ray diffraction and scanning electron microscopy. Different valences of Mn ions in Sr4Al14O25 were discriminated using the electron paramagnetic resonance and X-ray absorption near-edge structure spectroscopy techniques. The bond-valence theory was used to analyze the effective valences of Sr2+ and Al3+ in Sr4Al14O25. As a result, the strong covalence of Al3+ in the AlO4 tetrahedron other than in the AlO6 octahedron is disclosed. The deep red emission is attributed to Mn4+ occupying the center of AlO6 octahedron. The mechanism of energy transfer is mainly through dipole-dipole interaction, revealed by the analyses of critical distance and concentration quench. A high color rendering white LED prototype with color-rendering index up to Ra 93.23 packaged by using the red phosphor demonstrates its applicability. (C) 2014 Elsevier Ltd. All rights reserved.