Electrical and optical characterization of undoped BaTiO3 in the quenched state

文献情報

出版日 2009-03-20

DOI 10.1039/B823174E

インパクトファクター 3.676

著者

K.-D. Becker, M. Schrader, H.-S. Kwon, H.-I. Yoo

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要旨

On undoped polycrystalline BaTiO3−δ (99.9% nominal purity), that had been equilibrated and quenched at 1000 °C under different oxygen activities in the range of −19.4 ≤ log aO2 < 0.1, were measured optical reflectance spectra at 298 K and ac conductivity at 473, 523 and 573 K, respectively. It was observed that all specimens quenched at log aO2 > −17 are electrically insulating and white in color, once powdered, and show optical absorption only at the absorption edge at ∼3 eV. In contrast, those quenched at log aO2 < −17 are electronically conducting and dark and exhibit a significant absorption in the IR region. This demarcating oxygen activity for the conductivity transition is ca. 13 orders of magnitude lower than that for the n-to-p type transition (δ = 0) in the equilibrium state, contrary to expectation. It is, thus, suggested that contrary to the textbook knowledge, the hole traps responsible for the conductivity transition in undoped BaTiO3 may be variable-valent acceptor defects like MnTi. The strong IR absorption in the semiconducting state is ascribed to small-polaron (Ti′Ti) hopping processes.

掲載誌

Physical Chemistry Chemical Physics

CiteScore: 5.5

自己引用率: 10.3%

年間論文数: 3036

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