Powder Neutron Diffraction Studies of Na2Ti2Sb2O and Its Structure–Property Relationships

The structure of Na2Ti2Sb2O has been investigated by temperature-dependent powder neutron diffraction. Na2Ti2Sb2O crystallizes in I4/mmm symmetry. The structure of this phase can be viewed as an anti-K2NiF4 type where Ti3+ ion is located between two oxygen atoms forming a square-planar lattice. Powder neutron diffraction studies of Na2Ti2Sb2O indicate that this compound has a structural distortion in the [Ti2Sb2O]2− layer at T≈120 K. This transition corresponds well to the previously reported anomalous transition temperature of the magnetic susceptibility and electronic resistivity. Several models to explain the data are presented and discussed.