Structural investigation of perovskites
NaNbO3 Pbcm structure
Perovskites adopt the ABX3 structure, where A and B are cations of different sizes and X an anion, bonding to both cations in the structure. Perovskites are three-dimensional frameworks, consisting of corner-sharing BO6 octahedra. While cubic symmetry is exhibited in “ideal” perovskites, tilting and distortion of the octahedra and cation displacements often result in reduced or different symmetries. For example, the common form of NaNbO3 at room temperature is orthorhombic, with space group Pbcm.
We combine X-ray and neutron diffraction with multinuclear solid-state NMR and DFT calculations to gain a deeper understanding of structure and disorder in perovskites. Current interest is focussed determining structure and identifying phase transitions in NaNbO3 and the KNN (KxNa1–xNbO3) solid solution owing to their interesting dielectric properties, using 23Na, 93Nb, 39K and 17O NMR.
23Na MQMAS of NaNbO3 showing the presence of a two phase mixture
The ability of the perovskite structure to incorporate a large number of different cations and the corresponding structural variations, results in a range of applications.
