The role of π-bonding on the high temperature structure of the double perovskites Ba2CaUO6 and BaSrCaUO6.
The high temperature structural behaviour of the uranium perovskites Ba2CaUO6 and BaSrCaUO6 has been investigated using a combination of synchrotron X-ray and neutron powder diffraction. Ba2CaUO6 undergoes a complex sequence of structures associated with the progressive loss of cooperative octahedral tilting: P21/n → I2/m → I2/m → I4/m → Fm3[combining macron]m. The observation of the intermediate tetragonal structure, I4/m, in this, contrasts with the previously reported rhombohedral R3[combining macron] intermediate formed by the Ba2SrUO6 oxide. The importance of π-bonding in determining the structural sequence is discussed.
School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia. Brendan.Kennedy@Sydney.edu.au.
Emily
E
Reynolds
Gordon J
GJ
Thorogood
Maxim
M
Avdeev
Helen E A
HE
Brand
Qinfen
Q
Gu
Brendan J
BJ
Kennedy