New phosphors with strongly reduced content of critical raw materials for lighting applications

Aluminium silicate crystal is proposed as new promising inert matrix as host of luminescent ions. In particular, we studied the luminescence properties of single doped and multi-doped Al2SiO5 samples (doping elements: Ce, Tb, Cr, Fe, Zr) to explore their suitability as phosphors in modern lighting systems. The Al2SiO5 host matrix, obtained in nano-sized crystals belonging to the high temperature phase known as sillimanite, allows to narrow down the presence of rare earth elements exclusively to the dopants, thus providing a promising solution to the critical raw material concern. The crystals doped with Fe, Ce and Zr are mainly excited in the UV range, and they are good candidate as phosphors in compact fluorescent lamp systems. Terbium single doped samples are efficient phosphors in the green region with direct excitation in the deep UV region, but their excitation spectrum can be down-shifted to near UV range in in co-doped Ce:Tb samples. Indeed, thanks to the efficient energy transfer from cerium ions, the green emission from Tb ions can be excited by commercial AlGaN light emitting diode, suggesting Ce:Tb doped Al2SiO5 crystals as promising phosphors for green LED system