A Mossbauer study of oxygen vacancy and cation distribution in 6H-BaTi1-xFexO3-x/2

We have synthesized samples in the system BaTi1-xFexO3-x/2 with x = 0.1 - 0.6 at temperatures of 1200-1300degreesC under reducing conditions of oxygen fugacity. After drop quenching, samples were characterized using the electron microprobe, X-ray diffraction and Mossbauer spectroscopy. All samples were hexagonal with a 6H-BaTiO3 type structure. Mossbauer spectroscopy showed all iron to be present as Fe3+, occurring in octahedral and pentahedral sites. Analysis of area ratios indicates that oxygen vacancies are distributed randomly over 01 sites, and that a random distribution of Fe and Ti cations over M1 and M2 sites is consistent with the data. No evidence for ordering of oxygen vacancies was found. Results are consistent with conductivity results, which show generally increasing ionic conductivity with increasing oxygen vacancy concentration. (C) 2003 Elsevier Inc. All rights reserved.