Effect of the replacement of Al–O by Si–N on the properties of Sr6Si25.6Al6.4N41.6O4.4:Eu2+ phosphors for white light-emitting diodes

Abstract

Oxynitride phosphors Sr₆Si_25.6−xAl_6.4+xN_41.6−xO_4.4+x:Eu²⁺ are synthesized by gas pressure sintering of powder mixture of SrCO₃, AlN, Si₃N₄ and Eu₂O₃ at 1800 °C and 0.5 MPa of N₂ for 10 h, and their photoluminescence properties are investigated. Sr₆Si_25.6−xAl_6.4+xN_41.6−xO_4.4+x:Eu²⁺ can be efficiently excited over a broad spectral range between 300 and 500 nm, and exhibit an intense green emission centered at about 515 nm with a full width at half maximum of 65 nm due to the 4f⁶5d¹–4f⁷ transition of Eu²⁺ ions. The influence of the replacement of Si–N by Al–O on luminescence properties and crystal structure is reported in a series of Sr₆Si_25.6−xAl_6.4+xN_41.6−xO_4.4+x:Eu²⁺ phosphors. Different Sr sites are found in the crystal structure. The thermal quenching properties of the green phosphors are better than that of typical orthosilicate Ba₂SiO₄:Eu²⁺ phosphor. Their interesting photoluminescence properties indicate that the Sr₆Si_25.6Al_6.4N_41.6O_4.4 phosphor is a promising green emitting candidate for white LEDs applications.