Structures and crystal chemistry of the double perovskites Ba2LnB′O6 (Ln=lanthanide B′=Nb5+ and Ta5+): Part I. Investigation of Ba2LnTaO6 using synchrotron X-ray and neutron powder diffraction
Structures and crystal chemistry of the double perovskites Ba2LnB′O6 (Ln=lanthanide B′=Nb5+ and Ta5+): Part I. Investigation of Ba2LnTaO6 using synchrotron X-ray and neutron powder diffraction
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DOI：
10.1016/j.jssc.2007.08.009
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发表时间：
2007-11
影响因子：
3.3
通讯作者：
P. Saines;Jarrah R. Spencer;B. Kennedy;M. Avdeev
中科院分区：
文献类型：
--
作者：
P. Saines;Jarrah R. Spencer;B. Kennedy;M. Avdeev
The structure of 14 compounds in the series Ba{sub 2}LnTaO{sub 6} have been examined using synchrotron X-ray diffraction and found to undergo a sequence of phase transitions from I2/m monoclinic to I4/m tetragonal to Fm3-bar m cubic symmetry with decreasing ionic radii of the lanthanides. Ba{sub 2}LaTaO{sub 6} is an exception to this with variable temperature neutron diffraction being used to establish that the full series of phases adopted over the range of 15-500 K is P2{sub 1}/n monoclinic to I2/m monoclinic to R3-bar rhombohedral. The chemical environments of these compounds have also been investigated and the overbonding to the lanthanide cations is due to the unusually large size for the B-site in these perovskites. - Graphical abstract: The evolution of the structure across the series of double perovskites Ba{sub 2}LnTaO{sub 6} is established using a combination of synchrotron X-ray and neutron diffraction. The symmetry increases from monoclinic to tetragonal and then cubic as the size of the lanthanide decreases.
