Modified Phase Diagram for the Barium Oxide–Titanium Dioxide System for the Ferroelectric Barium Titanate

doi:10.1111/j.1551-2916.2007.01794.x

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Wiley InterScience

Journal of the American Ceramic Society

Volume 90 Issue 8, Pages 2589 - 2594

Published Online: 16 Jun 2007

Published on behalf of the American Ceramic Society (ACerS)

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Modified Phase Diagram for the Barium Oxide–Titanium Dioxide System for the Ferroelectric Barium Titanate

Soonil Lee ¹ ^† , Clive A. Randall ¹ and Zi-Kui Liu ²

¹ Center for Dielectric Studies, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802
² Phase Research Laboratory, Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802

^†Author to whom correspondence should be addressed. e-mail: leesoonil@gmail.com

T. Vanderah—contributing editor

ABSTRACT

The ferroelectric phase transition behavior in BaTiO₃ was investigated for various annealing times, temperatures, and Ba/Ti ratios by means of a differential scanning calorimeter. Coupling these observations with powder X-ray diffraction and transmission electron microscopy allowed new insights into the barium oxide (BaO)–titanium dioxide (TiO₂) phase diagram. The transition temperature was varied systematically with the Ba/Ti ratio at annealing temperatures from 1200° to 1400°C in air. The transition temperature decreased with increasing concentrations of BaO and TiO₂ partial Schottky defects, and showed a discontinuous change at the phase boundaries. Beyond the solubility region, two peritectoid reactions were confirmed and revised; first around 1150°C for Ba_1.054Ti_0.946O_2.946→Ba₂TiO₄+BaTiO₃ and second 1250°C for BaTi₂O₅→Ba₆Ti₁₇O₄₀+BaTiO₃, respectively. All other regimes of the BaO–TiO₂ were found to be consistent with the reported diagrams in the literature.