Luminescence properties of triple phosphate Ca8MgGd(PO4)7 : Eu2+for white light-emitting diodes

A novel Eu2+ ion doped triple phosphate Ca8MgGd(PO4)7 was synthesized by a general high-temperature solid-state reaction in a reductive atmosphere. X-ray powder diffraction analysis confirmed the formation of single phase Ca8MgGd(PO4)7. Scanning electron microscopy indicated that the microstructure of the phosphor consisted of irregular fine grains with a size of about 1–2 µm. Photoluminescence excitation spectrum measurements show that the phosphor can be efficiently excited by UV–visible light from 250 to 480 nm to realize emission in the visible range. The emission spectrum showed a broad and asymmetric profile from 410 to 750 nm, which corresponds to the allowed f–d transition from three kinds of Eu2+ ions. The characteristics indicated that this phosphor is a candidate for application in the white light-emitting diodes. The luminescence mechanism and three site occupancies of Eu2+ ions in Ca8MgGd(PO4)7 lattices are briefly discussed.