X-Ray Absorption Spectroscopy and Computer Modelling Study of Nanocrystalline Binary Alkaline Earth Fluorides

DOI: 10.1088/1757-899X/80/1/012005

Authors: A . V. Chadwick (University of Kent at Canterbury) , A. Duvel (Leibniz University of Hannover) , P. Heitjans (Leibniz University of Hannover) , D. M. Pickup (University of Kent) , S. Ramos (University of Kent) , D. C. Sayle (University of Kent) , T. X. T. Sayle (University of Kent)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Iop Conference Series: Materials Science And Engineering , VOL 80

State: Published (Approved)
Published: April 2015
Diamond Proposal Number(s): 8912

Abstract: Nanocrystalline samples of Ba1-xCaxF2 prepared by high-energy milling show an unusually high F- ion conductivity, which exhibit a maximum in the magnitude and a minimum in the activation energy at x = 0.5. Here, we report an X-ray absorption spectroscopy (XAS) at the Ca and Sr K edges and the Ba L3 edge and a molecular dynamics (MD) simulation study of the pure and mixed fluorides. The XAS measurements on the pure binary fluorides, CaF2, SrF2 and BaF2 show that high-energy ball-milling produces very little amorphous material, in contrast to the results for ball milled oxides. XAS measurements of Ba1-xCaxF2 reveal that for 0 < x <1 there is considerable disorder in the local environments of the cations which is highest for x = 0.5. Hence the maximum in the conductivity corresponds to the composition with the maximum level of local disorder. The MD calculations also show a highly disordered structure consistent with the XAS results and similarly showing maximum disorder at x = 0.5.

Subject Areas: Materials, Chemistry, Physics


Instruments: B18-Core EXAFS