Preparation and crystal structure of two types of zirconium phosphates by hydrothermal reaction

Single crystals of two types of zirconium phosphates, (NH₄) ₂[Zr₂(OH)₂(PO₄)₂(HPO ₄)] and (NH₄)Zr₂(PO₄)₃ were prepared under hydrothermal condition using diethylene glycol as a solvent and their crystal structures were determined by using single crystal X-ray diffraction data. The former compound has the layer structure built up by corner-sharing ZrO₆ octahedra and PO₄ tetrahedra, and NH⁺₄ ions were located in the interlayer space. This compound crystallized in the monoclinic system, space group C2/c (#15) and the unit cell parameters were a = 1.7093(4), b = 0.8748(2), c = 0.9216(2)nm and β = 103.69(2)° and the final R-factors were R = 0.066 and R_w = 0.121 for all 5982 reflections. This compound decomposed by releasing NH ⁺₄ ions in the interlayer above 300°C. The later compound has the cubic langbeinite-type structure in which NHNH⁺ ₄ ions were located in the tunnel and the structural refinement by using single crystal X-ray diffraction data was performed for the first time. This compound crystallized in the cubic system, space group P2₁3 (#198) and the unit cell parameters were a = 1.0198(2)nm and the final R-factors were R = 0.072 and R_w = 0.161 for all 1625 reflections. This compound also decomposed by releasing NHNH⁺₄ ions above 800°C.