Microstructure and electrical properties of BaFe 0.5Nb 0.5O 3 Doped with GeO 2 (1-5 wt.%)

Abstract

In this work, the effects of GeO2dopant on the electrical properties of BaFe0.5Nb0.5O3(BFN) perovskite ceramics were investigated. The BFN powder was prepared by a conventional mixed-oxide method using stoichiometric amounts of BaCO3, Fe2O3and Nb2O5. Afterward the GeO2contents, ranging from 1 to 5 wt.% were added to the calcined BFN powder and mixed via vibro-milling method. The mixtures were pressed and sintered at 1125-1150°C for 4 h to form dense ceramics. We showed that the addition of GeO2caused a reduction of grain size and formation of secondary phases: Ba3Fe2Ge4O14and BaGeO3. The maximum densities of these BFN doped with GeO2ceramics were slightly lower than those of the pure BFN due to the occurrence of pores. We also found that the GeO2doping could improve the dielectric properties of these ceramics at room temperature (25°C). The 1 wt.% GeO2doped sample exhibited higher dielectric constant of about 1800 and lower dielectric loss of 0.45 comparing to that of pure BFN. However, the dielectric constant values of these ceramics at high temperature (>25°C) were decreased significantly with the increase of GeO2concentration. In addition, the GeO2additive gave a weak ferroelectric behavior, leading to change in the pyroelectric coefficient and spontaneous polarization of the GeO2doped BFN ceramics. Copyright © Taylor & Francis Group, LLC.