The structures of molybdenum doped Ba2In2O5 were refined using X-ray and

neutron diffraction data at room and high temperature with the aim to derive

preferred oxygen diffusion pathways. At room temperature, refinement of

composition Ba2In2−xMoxO5+3x/2 with x = 0.1 revealed that molybdenum atoms

were preferentially located in the tetrahedral layers of the brownmillerite. At 700C,

the structure can be viewed as the stacking of alternating In and In/Mo octahedral

layers. The conduction process occurred preferentially in the latter which was

highly oxygen deficient. Preferred oxygen diffusion pathways were deduced from

joint probability density function and energy barriers were derived. It was in good

agreement with the activation energy deduced from impedance spectroscopy for

composition x = 0.1 at 950C. However, calculation of energy barrier assumes a

dynamic disorder of oxide ions which was unlikely to occur at lower temperature

and for sample containing a larger amount of molybdenum. Composition x = 0.5

was cubic on the whole range of temperature. At room temperature, the joint

probability density function revealed static disorder of the oxygen atoms, which

was likely due to the solution of molybdenum into the barium indium perovskite.

When temperature increases the disorder becomes more and more dynamic.

A Neutron Diffraction Study of the Oxygen Diffusion in Molybdenum Doped

Ba2In2O5. A.Rolle, P.Roussel, N.V.Giridharan, E.Suard, R.N.Vannier: Solid State

Ionics, 2008, 179[35-36], 1986-95