Temperature dependent x-ray diffraction study of lightly doped NaxWO3

Abstract

Temperature dependent x-ray diffraction studies have been carried out on nonstoichiometric lightly doped sodium tungsten bronze (NaxWO3 for x=0.025). The investigation reveals a structural modification around 230 K. Although the high and low temperature phases are monoclinic but at low temperature the corner sharing WO6 octahedra get significantly distorted due to displacement of tungsten and oxygen atoms from its mean position. This structural modification induces polaron formation in Na0.025WO3 below 230 K.