EN21.04.02 : Ionic Conductivity in Ion Exchanged Niobates/Titanates of Pyrochlore Structure

5:00 PM–7:00 PM Apr 4, 2018

PCC North, 300 Level, Exhibit Hall C-E

Alicia Brune1 Kurt Leinenweber1 William Petuskey1

1, Arizona State University, Tempe, Arizona, United States

A decade ago we reported (Alicia B. Brune; Robert I. Mangham; William T. Petuskey in Journal of Materials Science 43(2), 621 (2008)) on the preparation and characterizations of two hydrogenated pyrochlores (abbreviated as HPN and HPNT) obtained from the corresponding oxides Pb1.5Nb2O6.5 (PN) and Pb2Nb1.33Ti0.67O6.67 (PNT), by ion exchange in acidic aqueous media. Measured electrical conductivities were attributed to dominant proton transport. Now, complementary data are presented supporting such interpretation and providing insights on transport mechanisms. Information on hydroxyl groups, proton dynamics, and proton locations was acquired by infrared and Raman spectroscopy, solid state 1H NMR, and neutron diffraction, respectively. Results suggest that proton transport occurs through tunnels within the bulk of the pyrochlore structure, in addition to surface transport at the lower temperatures. Tunnel dimensions are shown to formally allow the transport of larger ions, with the role of lattice dynamics being unknown. Findings are compared to literature data on pyrochlores, particularly those obtained by ion exchange. Applications of HPN and HPNT in ion transport membranes face challenges regarding densification and structural stabilization.