Electrical circuit modeling for the relaxor response of bismuth magnesium tantalate pyrochlore

Abstract

The electrical properties of bismuth magnesium tantalate pyrochlore, Bi_3.30Mg_1.88Ta_2.82O_13.88 (BMT) were investigated by both inductor-capacitor-resistor (LCR) and impedance spectroscopy techniques covering a broad temperature range of 10–1073 K and a frequency range of 5 Hz - 1 MHz. At below ∼180 K, BMT pyrochlore exhibited interesting relaxor behaviour that showed high dispersion characteristics in its frequency-temperature dependent dielectric constants, ε′ and dielectric losses, tan δ, respectively. The maximum ε′_max of ∼77 was obtained at the temperature maximum, T_m of 154 K. The frequency-independent ε′ data above 154 K at a fixed frequency of 1 MHz can be well fitted with the Curie-Weiss law and the relaxation features of Bi_3.30Mg_1.88Ta_2.82O_13.88 obeyed the Vogel-Fulcher equation. The dielectric properties of Bi_3.30Mg_1.88Ta_2.82O_13.88 relaxor in the low temperature range of 20–320 K could be satisfactorily modeled with different equivalent circuits. In this perspective, a master circuit consisting of a parallel R-C-CPE element in series with a capacitor was required to accurately fit the low temperature data.