Ca[LiAl<sub>3</sub>N<sub>4</sub>]:Eu<sup>2+</sup>A
Narrow-Band Red-Emitting Nitridolithoaluminate
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Abstract
Ca[LiAl<sub>3</sub>N<sub>4</sub>]:Eu<sup>2+</sup> 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<sup>–1</sup> (∼60 nm). Ca[LiAl<sub>3</sub>N<sub>4</sub>]:Eu<sup>2+</sup> was synthesized from Ca, LiAlH<sub>4</sub>, LiN<sub>3</sub>, AlF<sub>3</sub>, and EuF<sub>3</sub> 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[Li<sub>3</sub>SiO<sub>4</sub>], the compound
forms a highly condensed framework of AlN<sub>4</sub> and LiN<sub>4</sub> tetrahedra [<i>I</i>4<sub>1</sub>/<i>a</i> (no. 88), <i>Z</i> = 16, <i>a</i> = 11.1600(16)
Å, and <i>c</i> = 12.865(3) Å] 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, κ = 1. The Ca site is positioned in
the center of <i>vierer</i> 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