Samples which had brownmillerite-related structures were prepared, and the ionic conductivity after the reduction of NO to N2 was investigated. It was found that the conductivity increased at the order-disorder transition temperatures for O vacancies in these compounds (figure 6). The ionic conductivity contributed to the catalytic activity of NO reduction to N2.

T.Mori, H.Yamamura, H.Ogino, H.Kobayashi, T.Mitamura: Journal of the American Ceramic Society, 1994, 77[10], 2771-2