Journal Article

Doping mechanisms and electrical properties of bismuth tantalate fluorites

Chen, S. K., Tan, K. B., Khaw, C. C., Zainal, Z., Tan, Y. P., Firman, K.

2017

Overview

Phase-pure bismuth tantalate fluorites were successfully prepared via conventional solid-state method at 900 °C in 24–48 h. The subsolidus solution was proposed with the general formula of Bi 3+ x Ta 1− x O 7− x (0 ≤  x  ≤ 0.184), wherein the formation mechanism involved a one-to-one replacement of Ta 5+ cation by Bi 3+ cation within ~4.6 mol% difference. These samples crystallised in a cubic symmetry, space group Fm-3 m with lattice constants, a  =  b  =  c in the range 5.4477(± 0.0037)–5.4580(± 0.0039) Å. A slight increment in the unit cell was discernible with increasing Bi 2 O 3 content, and this may attribute to the incorporation of relatively larger Bi 3+ cation in the host structure. The linear correlation between lattice parameter and composition variable showed that the Vegard’s law was obeyed. Both TGA and DTA analyses showed Bi 3+ x Ta 1− x O 7− x samples to be thermally stable as neither phase transition nor weight loss was observed within ~28–1000 °C. The AC impedance study of Bi 3 TaO 7 samples was performed over the frequency range 5–13 MHz. At intermediate temperatures, ~350–850 °C, Bi 3+ x Ta 1− x O 7− x solid solution was a modest oxide ion conductor with conductivity, ~10 −6 –10 −3 S cm −1 ; the activation energy was in the range 0.98–1.08 eV.

• Publisher: Springer US,Springer,Springer Nature B.V
• Subject: activation energy / bismuth / Bismuth oxides / Bismuth trioxide / Cations / Ceramics / Characterization and Evaluation of Materials / Chemistry and Materials Science / Classical Mechanics / Conductors / Crystallography and Scattering Methods / Cubic lattice / Electrical properties / Electrical resistivity / Frequency ranges / Lattice parameters / Materials Science / phase transition / Phase transitions / Polymer Sciences / Solid Mechanics / Solid solutions / temperature / Thermal stability / Unit cell / Weight loss