Self-Activated Yellow Light Emitting Phosphors of α, β-Ca3B2N4 with Long Afterglow Properties

Defect luminescence has been considered to be one of the most efficient ways to resolve the problem of the recent limited supply and increased demand for rare-earth elements. So, in this work, a novel self-activated long-persistent green-yellow and yellow emitting phosphors of α-Ca3B2N4 and β-Ca3B2N4 has been successfully synthesized by sample-pressuring sintering. The α-Ca3B2N4 and β-Ca3B2N4 all have a broad excitation band peaked at 300 and 350 nm and emit yellow-green light peaked at 550 nm and yellow light peaked at 575 nm respectively with the long afterglow properties. The crystal structures and electron structures of α-Ca3B2N4 and β-Ca3B2N4 have been investigated to show that orthorhombic β-Ca3B2N4 corresponds to an ordered superstructure of cubic α-Ca3B2N4 and the phase transformation between α-Ca3B2N4 and β-Ca3B2N4 would happen during the preparation process, which produces many intrinsic defects forming the luminescent center. The thermoluminescence (TL) curve shows that there are traps in the h...