Europium Lithosilicates\nLi<sub>2</sub>EuSi<sub>2</sub>N<sub>4</sub> and Li<sub>2</sub>EuSiO<sub>4</sub>Crystal\nStructures and Luminescence

With Li<sub>2</sub>EuSi<sub>2</sub>N<sub>4</sub>, the\nend member\nof the solid-solution series set up by substituting the divalent cation\nin the well-known host materials Li<sub>2</sub>CaSi<sub>2</sub>N<sub>4</sub> and Li<sub>2</sub>SrSi<sub>2</sub>N<sub>4</sub> with Eu(II)\ncould be synthesized and described by means of single-crystal X-ray\ndiffraction and single-grain luminescence spectroscopy. The new compound\ncrystallizes isotypically to Li<sub>2</sub>CaSi<sub>2</sub>N<sub>4</sub> and Li<sub>2</sub>SrSi<sub>2</sub>N<sub>4</sub> in cubic space group <i>Pa</i>3̅ (no. 205) with a lattice parameter of <i>a</i> = 10.7049(2) Å and a cell volume of <i>V</i> = 1226.73(7) Å<sup>3</sup>. Irradiated with blue light, Li<sub>2</sub>EuSi<sub>2</sub>N<sub>4</sub> exhibits a narrow-band red emission\n(λ<sub>max</sub> = 628 nm, 1.97 eV, 15924 cm<sup>–1</sup>; fwhm = 83 nm, 0.27 eV, 2143 cm<sup>–1</sup>). Also for Li<sub>2</sub>EuSiO<sub>4</sub>, the end member of the solid-solution series\nof Li<sub>2</sub>SrSiO<sub>4</sub> with Sr(II) substituted by Eu(II),\nluminescence emission could be measured on a single crystal (λ<sub>max</sub> = 595 nm, 2.05 eV, 16798 cm<sup>–1</sup>; fwhm =\n116 nm, 0.40 eV, 3211 cm<sup>–1</sup>). In this paper, both\ncompounds are being compared with other known members of their solid-solution\nseries regarding structure and luminescence properties.