Crystal Structure of Na2ZnP2O7: Reinvestigation

In the context of a detailed investigation of the luminescent properties of the Na 2− x Ag x ZnP 2 O 7 compounds, the structure of the pure sodium phosphates was “revisited.” The crystal structure of Na 2 ZnP 2 O 7 has been determined by X-ray diffraction using single crystals. A new model explaining the actual large unit cell ( a = b =2177.1(3) pm, c =1028.5(2) pm, P4 2 / n , Z =32) was determined by assuming the existence of twins. The structure is made up of [ZnP 2 O 7 ] layers consisting of corners sharing [P 2 O 7 ] groups and [ZnO 4 ] tetrahedra, and the sodium atoms are located between the layers in 7- or 8-fold coordinated sites. This model is discussed with respect to the crystal chemistry of the monovalent cation zinc phosphate.