Solid State Science and Technology, Vol. 15, No 1 (2007) 156-162

ISSN 0128-7389

Corresponding Author:




C.C. Khaw, C.K. Lee, Z. Zainal, Y.P. Tan and Y.H. Taufiq-Yap

Chemistry Department, Universiti Putra Malaysia

43300 Serdang, Selangor



The subsolidus phase diagram of the system Bi2O3-ZnO-Ta2O5 in the region of the cubic pyrochlore phase has been determined at 1050oC. This phase forms a solid solution area that includes the ideal composition P, Bi3Zn2Ta3O14. Possible solid solution mechanisms for the cubic pyrochlore phase are proposed. Density measurements of Zn deficient solid solutions were carried out in order to determine the possible solid solution formation mechanisms. The general formula of the solid solutions is proposed to be Bi3+yZn2-xTa3-yO14-x-y, based on the mechanisms of Zn/oxide ion vacancies and variable Bi/Ta ratio. Solid solution series at x = 0 and y = 0 were investigated using impedance spectroscopy for their dielectric properties. These materials appeared to be dielectric. Bi3Zn2Ta3O14 has ε of 42 at 30oC and 1 MHz; ε for the solid solutions range from 39 to 65. A high degree of dispersion on the permittivity at low frequencies (<1 kHz) and temperatures above 600oC is apparent.



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