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Crystal structure of Ln1/3NbO3 (Ln=Nd, Pr) and phase transition in Nd1/3NbO3 |
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| Authors: | Zhaoming Zhang Christopher J. Howard Kevin S. Knight |
| Affiliation: | a Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234, Australia b School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia c ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, UK |
| Abstract: | The crystal structure of the A-site deficient perovskite Ln1/3NbO3 (Ln=Nd, Pr) at room temperature has been determined, for the first time, as orthorhombic in space group Cmmm using high-resolution neutron powder diffraction. Pertinent features are the alternation of unoccupied layers of A-sites and layers partly occupied by Ln cations, as well as out-of-phase tilting of the NbO6 octahedra around an axis perpendicular to the direction of the cation/vacancy ordering. The phase transition behaviour of Nd1/3NbO3 has also been studied in situ. This compound undergoes a continuous phase transition at around 650 °C to a tetragonal structure in space group P4/mmm due to the disappearance of the octahedral tilting. The analysis of spontaneous strains shows that this phase transition is tricritical in nature. |
| Keywords: | Perovskites Crystal structures Octahedral tilting Cation/vacancy ordering Phase transition Neutron powder diffraction |
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