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Strobel, Philipp; Weiler, Volker; Schmidt, Peter J.; Schnick, Wolfgang (2018): Sr[BeSi2N4]:Eu2+/Ce3+ and Eu[BeSi2N4]: Nontypical Luminescence in Highly Condensed Nitridoberyllosilicates. In: Chemistry - A European Journal, Vol. 24, No. 28: pp. 7243-7249
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M[BeSi2N4] (M=Sr,Eu), crystallizing in the hexagonal space group P (6) over bar 2c, was synthesized from Sr(NH2)(2), Be3N2, and "Si(NH)(2)" in W crucibles under a N-2 atmosphere in a radio-frequency furnace. The crystal structure was solved from powder X-ray diffraction data by the charge-flipping method (Sr[BeSi2N4]: a=4.86082(2), c=9.42264(4)angstrom, Z=2;Eu[BeSi2N4]: a=4.85848(1), c=9.41615(4)angstrom). M[BeSi2N4] contains a highly condensed rigid network of trigonal planar [BeN3] units that are connected to Si2N7 double tetrahedra by common vertices. M[BeSi2N4] (M=Sr,Eu) are the first examples of nitridoberyllosilicates and are isotypic to the oxoberyllate Sr[Be3O4]. Eu2+-doped Sr[BeSi2N4] and Eu[BeSi2N4] show orange-trapped exciton emission (lambda(em)=605nm, fwhm approximate to 126nm), whereas Ce3+-doped samples of Sr[BeSi2N4] show nontypical yellowish-orange luminescence. Sr[BeSi2N4] has a large band gap of approximate to 4.4eV and shows high chemical and thermal stability. Eu2+-doped beryllates with regular 4f(6)5d(1)4f(7)-emission could be interesting for future application in LEDs upon doping with Eu2+ or Ce3+ due to large band gaps, rigid networks, and chemical and thermal stability.