A temperature-dependent structural investigation of electrical transitions in A(3)conb(2)O(9) perovskites (A = Ca2+, Sr2+, Ba2+)

摘要

Upon heating, the 1:2 triple perovskites A(3)CoNb(2)O(9) (A = Ca, Sr or Ba) each undergo well-defined insulator to conductor phase transitions at similar to 8, similar to 126 and similar to 325 degrees C, respectively. As the trend in the transition temperatures for these materials does not correlate with the size of the reported band gaps, neutron powder diffraction has been used to investigate if this change in electrical behaviour of the materials was due to a structural phase change. It was found that in the regions of the suspected phase transitions there were only slight perturbations of the structures, namely thermal expansion of the lattices and an apparent muting of the amplitude of the octahedral rotations in the A = Ca and Sr compound at higher temperatures. (c) 2006 Elsevier B.V. All rights reserved.