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

Abstract

New zinc phosphate Li_0.5Na_0.15K_0.85ZnP₂O_6.75 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 R_obs = 0.052; a = 14.609 (7) Å, b = 6.898 (5) Å, and c = 14.603 (7) Å; 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.