Ca[LiAl3N4]:Eu2+-A Narrow-Band Red-Emitting Nitridolithoaluminate

Ca[LiAl3N4]:Eu2+ is an intriguing new narrow-band red-emitting phosphor material with potential for application in high-power phosphor-converted light-emitting diodes (pc-LEDs). With excitation by blue InGaN-based LEDs, the compound exhibits an emission maximum at 668 nm with a full width at half maximum of only 1333 cm(-1) (similar to 60 nm). Ca[LiAl3N4]:Eu2+ was synthesized from Ca, LiAlH4, LiN3, AlF3, and EuF3 in weld-shut Ta ampules, and the structure was solved and refined on the basis of single-crystal X-ray diffraction data. After isotypical crystallization with Na[Li3SiO4], the compound forms a highly condensed framework of AlN4 and LiN4 tetrahedra [I4(1)/a (no. 88), Z = 16, a = 11.1600(16) angstrom, and c = 12.865(3) angstrom] and can thus by classified as a nitridolithoaluminate. Both types of polyhedra are connected to each other by common edges and corners, yielding a high degree of condensation, kappa = 1. The Ca site is positioned in the center of vierer ring channels along [001] and coordinated in a cuboidal manner by eight N atoms. To validate the presence of Li, transmission electron microscopy (TEM) investigations employing electron energy-loss spectroscopy (EELS) were carried out. Furthermore, to confirm the electrostatic bonding interactions and the chemical composition, lattice energy calculations [Madelung part of lattice energy (MAPLE)] have been performed.