Ba(4)Al(7)Li(28.08)O(26.92)N(1.08), the Barium Oxonitridolithoaluminate with a Highly Condensed LiO(4) Tetrahedra Framework

[Image: see text] The new compound Ba(4)Al(7)Li(28.08)O(26.92)N(1.08) consists of AlO(4)/AlO(3)N tetrahedra, 10-fold coordinated Ba(2+) cations, and a highly condensed edge- and corner-sharing LiO(4) tetrahedra framework, which leads to a degree of condensation greater than 1. The first barium oxonitridolithoaluminate was synthesized by a high-temperature solid-state reaction in a weld-shut tantalum ampoule and the crystal structure has been determined by single-crystal X-ray diffraction. Ba(4)Al(7)Li(28.08)O(26.92)N(1.08) crystallizes in the monoclinic space group P2(1)/m (no. 11) with the lattice parameters a = 1052.41(3), b = 615.93(2), c = 1088.45(4) pm, β = 98.86(1)°, and a volume of V = 0.69712(4) nm(3). In addition, Ba(4)Al(7)Li(28.08)O(26.92)N(1.08) doped with the activator ion Eu(2+), exhibits a broad band emission with a maximum at λ(max) = 524 nm (2.34 eV) with a fwhm of 112 nm (4373 cm(–1)/0.54 eV), which can be described by a superposition of two adjusted emission bands at λ(max) = 515 nm (2.41 eV) with a fwhm of 70 nm (2704 cm(–1)/0.34 eV), and at λ(max) = 574 nm (2.18 eV) with a fwhm of 127 nm (4127 cm(–1)/0.51 eV).