Sr(5)Al(5+x)Si(21-x)N(35-x)O(2+x):Eu2+ (x approximately 0)--a novel green phosphor for white-light pcLEDs with disordered intergrowth structure.
Sr(5)Al(5+x)Si(21-x)N(35-x)O(2+x) (x approximately 0) was obtained by high-temperature synthesis (1600 to 1750 degrees C). Upon doping with Eu(2+), the thermally very stable material shows an efficient broadband emission in the green spectral range (lambda(max) approximately 510 nm, FWHM = 69 nm) under UV to blue light excitation. The compound exhibits a complex intergrowth structure (space group Pmn2(1) (no. 31); a = 23.614, b = 7.487, c = 9.059 A; V = 1601.5(6) A(3); Z = 2, R1 = 0.067), which consists of highly condensed dreier ring layers alternating with sechser ring layers that include both vertex- and edge-sharing (Si,Al)(O,N)(4) tetrahedra. Both layer types exhibit pseudotranslational symmetry, which leads to a more or less pronounced disorder of the sechser ring layers. The Sr atoms are located in channel-like voids of the silicate framework with coordination number nine. The compound has been characterized by single-crystal and powder X-ray diffraction, as well as high-resolution electron microscopy and electron diffraction. The structure and chemical composition has been confirmed by (29)Si solid-state NMR spectroscopy, lattice energy calculations, and diverse elemental analyses.
Department Chemie und Biochemie, Lehrstuhl für Anorganische Festkörperchemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 München, Germany.
Oliver
O
Oeckler
Juliane A
JA
Kechele
Hans
H
Koss
Peter J
PJ
Schmidt
Wolfgang
W
Schnick