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Polymorphism in the family of Ln6−xMoO12−δ (Ln = La, Gd–Lu; x = 0, 0.5) oxygen ion- and proton-conducting materialsстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 5 июня 2017 г.
- Авторы: Shlyakhtina A.V., Savvin S.N., Lyskov N.V., Kolbanev I.V., Karyagina O.K., Chernyak S.A., Shcherbakova L.G., Núñez P.
- Журнал: Journal of Materials Chemistry A
- Том: 5
- Год издания: 2017
- Издательство: Royal Society of Chemistry
- Местоположение издательства: United Kingdom
- Первая страница: 7618
- Последняя страница: 7630
- DOI: 10.1039/C6TA09963G
- Аннотация: The formation of Ln6−xMoO12−δ (Ln = La, Gd, Dy, Ho, Er, Tm, Yb, Lu; x = 0, 0.5) rare-earth molybdates from mechanically activated oxide mixtures has been studied in the range 900–1600 °C. The morphotropy and polymorphism (thermodynamic phase and kinetic (growth-related) transitions) of the Ln6−xMoO12−δ (Ln = La, Gd–Lu; x = 0, 0.5) molybdates have been analyzed in detail. As a result we have observed two new types of oxygen ion- and proton-conducting materials with bixbyite (Ia[3 with combining macron], no. 206) and rhombohedral (R[3 with combining macron], no. 148) structures in the family of Ln6−xMoO12−δ (Ln = La, Gd–Lu; x = 0, 0.5) molybdates. The heavy rare-earth molybdates Ln6−xMoO12−δ (Ln = Er, Tm, Yb; x = 0, 0.5) have been shown for the first time to undergo an order–disorder (rhombohedral–bixbyite) phase transition at 1500–1600 °C, and we have obtained compounds and solid solutions with the bixbyite structure (Ia[3 with combining macron]). The stability range of the rhombohedral phase (R[3 with combining macron]) increases with decreasing Ln ionic radius across the Ln6−xMoO12−δ (Ln = Er, Tm, Yb, Lu) series. We have detected a proton contribution to the conductivity of the rhombohedral La5.5MoO11.25 (2 × 10−4 S cm−1 at 600 °C in wet air) and high-temperature polymorph Yb6MoO12−δ bixbyite structure, (Ia[3 with combining macron]) below 600 °C. At these temperatures, rhombohedral (R[3 with combining macron]) Yb6MoO12 seems to be an oxygen ion conductor (Ea = 0.53–0.58 eV). The total conductivity of rhombohedral (R[3 with combining macron]) Yb6MoO12 exceeds that of bixbyite Yb6MoO12−δ by more than one order of magnitude and is 3 × 10−5 S cm−1 at 500 °C. According to their high-temperature (T > 600 °C) activation energies, the lanthanum and ytterbium molybdates studied here are mixed electron–ion conductors.
- Добавил в систему: Черняк Сергей Александрович