Extended dielectric constant step from −80 °C to 336 °C in the BaTiO3–BiYO3–Ba(Fe0.5Nb0.5)O3 system

Abstract

Polycrystalline 0.8BaTiO₃–(0.2 − x)BiYO₃–xBa(Fe_0.5Nb_0.5)O₃ (0.8BT–(0.2 − x)BY–xBFN) (x = 0–0.04) ceramics were fabricated via a conventional solid-state reaction method. The phase transition, microstructure and dielectric properties were obtained by X-ray diffraction and dielectric measurements as functions of chemical composition and temperature. A progressive decline in ε_rmax with increasing x leads to nearly temperature-stable dielectric properties over a wide temperature range. For x ≥ 0, dielectric measurements indicate relaxor behavior. Increasing the BFN content effectively improves the dielectric temperature stability of BT ceramics. For x = 0.02, ε_r = 590 ± 15% from −48 °C to 326 °C, and tan δ ≤ 0.02 across the temperature range of −13 °C to 156 °C. For x = 0.04, ε_r = 540 ± 15% from −80 °C to 336 °C, and tan δ ≤ 0.02 across the temperature range of −22 °C to 231 °C. The plot of ac conductivity for x = 0.04 shows the NTCR character of the compounds, and the activation energy of the dc conductivity is not far from the electron from second ionization energy of oxygen vacancies.