Synthesis, Crystal Structure, Raman, and Magnetic Properties of Li₄Sr₂Mn₂P₄

Recently the crystal chemistry of ternary and quaternary lithium phosphide-trielates and phosphide-tetrelates has been investigated due to the remarkable lithium ion conductivity of some representatives. Herein, the extension of the quarternary Zintl phase Li₄Sr₂SiP₄ to a member comprising transition metals is reported. Li₄Sr₂Mn₂P₄ crystallizes as a disordered variant of the trigonal Li₃LaSb₂ structure type (space group P (Formula presented.) m1, no. 164) with lattice parameters a = 4.2367(6) Å and c = 7.110(1) Å. It exhibits the Li:M ratio (M = Mn, Al) in tetrahedral voids known from Li₂Sr₂Al₂P₄ but crystallizes isotypically to Li₅Sr₂AlP₄. In addition, magnetic properties and Raman spectra are reported and discussed. While Li₄Sr₂Mn₂P₄ can formally be described in analogy to the mentioned quarternary Zintl phases, magnetic measurements indicate that it is not a Zintl phase itself.