Finding Order in Disorder: The Highly Disordered Lithium Oxonitridophosphate Double Salt Li_8+x P₃ O_10-x N_1+x...

The crystalline lithium oxonitridophosphate Li_8+x P₃ O_10-x N_1+x , was obtained in an ampoule synthesis from P₃ N₅ and Li₂ O. The compound crystallizes in the triclinic space group P $$ with a=5.125(2), b=9.888(5), c=10.217(5) Å, α=70.30(2), β=76.65(2), γ=77.89(2)°. Li_8+x P₃ O_10-x N_1+x is a double salt, the structure of which contains distinctive complex anion species, namely non-condensed P(O,N)₄ tetrahedra, and P(O,N)₇ double tetrahedra connected by one N atom. Additionally, there is mixed occupation of O/N positions, which enables further anionic species by variation of O/N occupancies. To characterize these motifs in detail, complementary analytical methods were applied. The double tetrahedron exhibits significant disorder in single-crystal X-ray diffraction. Furthermore, the title compound is a Li⁺ ion conductor with a total ionic conductivity of 1.2×10^-7  S cm^-1 at 25 °C, and a corresponding total activation energy of 0.47(2) eV.