Citation
Chon, M. P. and Tan, Kar Ban and Khaw, Chwin Chieh and Zainal, Zulkarnain and Yap, Taufiq Yun Hin and Chen, Soo Kien and Tan, P. Y.
(2016)
Subsolidus phase equilibria and electrical properties of pyrochlores in the Bi2O3–CuO–Ta2O5 ternary system.
Journal of Alloys and Compounds, 675.
pp. 116-127.
ISSN 0925-8388; ESSN: 1873-4669
Abstract
Subsolidus phase relations had been determined for the Bi2O3–CuO–Ta2O5 (BCT) system over the temperature range 700–950 °C in air. Two structurally distinct ternary phases of different symmetries, a cubic pyrochlore and a monoclinic zirconolite were observed. Phase-pure pyrochlores existed in a unique boomerang-shaped area, which could be described using the general formula, Bi2.48+yCu1.92−xTa3.6+x−yO14.64+3x/2−y: 0.00(1) ≤ x ≤ 0.80(1) and 0.00 (1) ≤ y ≤ 0.60(1), respectively. BCT subsolidus pyrochlores exhibited low electrical conductivities, 10−7–10−6 S cm−1, moderate dielectric constants, ε′, ∼60–80 and low dielectric losses, tan δ, ∼0.01–0.20 at 1 MHz and ambient temperature, ∼28 °C. The recorded low activation energies, 0.32–0.40 eV suggesting these electroceramics were of semiconductor-type at elevated temperatures.
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