The Crystal Structure and Thermal Expansion of Zinc Phosphate Li0.5Na0.15K0.85ZnP2O6.75

New zinc phosphate Li0.5Na0.15K0.85ZnP2O6.75 is obtained by the crystallization of a melt and its crystal structure is determined by the single crystal X-ray diffraction data. It is monoclinic and is refined in the space group P21/n to Robs = 0.052; a = 14.609 (7) A, b = 6.898 (5) A, and c = 14.603 (7) A; and β = 118.59 (5)°. The crystal structure is formed by a framework consisting of the PO4, ZnO4, and LiO4 tetrahedra. The ordering of Zn, Li, Na, and K cations and vacancies leads to the formation of a two fold superstructure. The compound belongs to the MM'ZnP2O7 structural family, the connection with which is under discussion. The thermal expansion is anisotropic, thus, α11 = 5, α22 = 29, and α33 = 9 × 10−6°C−1.