Increased Synthetic Control-Gaining Access to Predicted Mg₂ Si₅ N₈ and β-Ca₂ Si₅ N₈

Nitridosilicates represent an intriguing class of materials and are typically made up of highly condensed tetrahedral network structures. Alkaline-earth nitridosilicates emerged as unique host materials for Eu²⁺ doped luminophores which found broad application in phosphor-converted (pc)-LEDs. In contrast to common strategies of preparing nitridosilicates by bottom-up syntheses, we have now succeeded to post-synthetically design nitridosilicates by ion exchange in metal halide melts. We describe the syntheses of hitherto unknown but predicted alkaline-earth nitridosilicates, Mg₂ Si₅ N₈ and β-Ca₂ Si₅ N₈ . Both compounds were obtained by ion exchange starting from pre-synthesized nitridosilicates. In situ investigations of the ion-exchange process show that the Si-N network topology remains preserved. Therefore the reaction offers a significant increase of synthetic control with respect to classical bottom-up syntheses.