Issue 17, 2009
From the journal:

Physical Chemistry Chemical Physics

Electrical and optical characterization of undoped BaTiO3 in the quenched state

K.-D. Becker,a   M. Schrader,a   H.-S. Kwonb  and  H.-I. Yoo*b  

* Corresponding authors

a Institute of Physical and Theoretical Chemistry, Technische Universität Braunschweig, Braunschweig, Germany
E-mail: k-d.becker@tu-bs.de

b Department of Materials Science and Engineering, Seoul National University, Seoul, Korea
E-mail: hiyoo@snu.ac.kr

Abstract

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.

Graphical abstract: Electrical and optical characterization of undoped BaTiO3 in the quenched state

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Article information

DOI
https://doi.org/10.1039/B823174E
Article type
Paper
Submitted
05 Jan 2009
Accepted
17 Feb 2009
First published
20 Mar 2009

Phys. Chem. Chem. Phys., 2009,11, 3082-3089

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Electrical and optical characterization of undoped BaTiO3 in the quenched state

K.-D. Becker, M. Schrader, H.-S. Kwon and H.-I. Yoo, Phys. Chem. Chem. Phys., 2009, 11, 3082 DOI: 10.1039/B823174E

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