Synthesis, Crystal Structure, Raman, and Magnetic Properties of Li ₄ Sr ₂ Mn ₂ P ₄

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 Li 4 Sr 2 SiP 4 to a member comprising transition metals is reported. Li 4 Sr 2 Mn 2 P 4 crystallizes as a disordered variant of the trigonal Li 3 LaSb 2 structure type (space group P m 1, 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 Li 2 Sr 2 Al 2 P 4 but crystallizes isotypically to Li 5 Sr 2 AlP 4 . In addition, magnetic properties and Raman spectra are reported and discussed. While Li 4 Sr 2 Mn 2 P 4 can formally be described in analogy to the mentioned quarternary Zintl phases, magnetic measurements indicate that it is not a Zintl phase itself.