Abstract
The structure of triclinic disodium hafnium disilicate, Na(2)HfSi(2)O(7), has been determined by laboratory powder X-ray diffraction and refined by the Rietveld refinement. The structure is a framework made of alternate layers of HfO(6) octa-hedra and SiO(4) tetra-hedra linked by common O atoms. Sodium atoms are located in the voids of the framework, aligned into tunnels along the [010] direction. Na(2)HfSi(2)O(7) is isostructural with the parakeldyshite Na(2)ZrSi(2)O(7) phase.