The new phosphor RbKLi2[Li3SiO4]4:Eu2+ was synthesized by different high-temperature solid-state reactions. It is accessible from the alkali metal carbonates, SiO2, and Eu2+ as a luminous active cation either in closed tantalum ampoules or by conventional solid-state reaction in nickel crucibles, under a constant flow of forming gas. The structure of the thereby received rod-shaped crystals was solved and refined on the basis of single crystal X-ray diffraction data. The compound crystallizes isostructurally to CsKNa2[Li3SiO4]4 and forms a highly condensed network of LiO4 and SiO4 tetrahedra [I4/m (no. 87), Z = 2, a = 10.9508(6) and c = 6.3334(3) Å]. It is a new member of the recently discovered family of alkali lithosilicate phosphors. Under excitation with UV to blue light, the compound exhibits interesting luminescence properties. Depending on the mode of synthesis, either green or blue luminescence of the samples is observed. Both emission profiles can be described as ultra-narrow-banded, since the full width at half maximum (fwhm) is below 0.2 eV. The green phosphor shows an emission maximum at 532 nm with a fwhm of 43.5 nm (0.193 eV) and the blue one at 474 nm with a fwhm of 24.8 nm (0.137 eV). Furthermore, the material presented here allows a more detailed localization of the luminescence center inside the structure, which may allow a better understanding of the luminescence properties of many other alkali lithosilicate phosphors.

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The cerium phosphide tellurides Ce 3 Te 4Ϫx P x (x Յ 1), CeTe 2Ϫx P x (x ഠ 0.35Ϫ0.55) and CeTe 2Ϫy P y (y տ 1) have been synthesised from the elements or from oxides in a thermite-type reaction. Both ways have been optimised by consideration of the thermodynamic behaviour of the compounds. Hence the investigation of phase equilibria in the ternary system Ce/Te/P and of the thermal decomposition of ternary phases was necessary. This