Reduced dielectric loss and enhanced piezoelectric properties of Mn modified 0.71BiFeO₃–0.29BaTiO₃ ceramics sintered under oxygen atmosphere

0.71BiFeO₃–0.29BaTiO₃ piezoelectric ceramics with Mn modification (BF–BT–x %Mn) sintered in air and O₂ atmospheres have been investigated to understand the effects of sintering atmosphere on structure, dielectric, ferroelectric and piezoelectric properties. All ceramics exhibited the pseudo-cubic phase, while the O₂ sintered ceramics possessed larger grain sizes and more homogeneous distribution. Dielectric, ferroelectric and piezoelectric properties of BF–BT–xMn ceramics were improved obviously after O₂ atmospheres sintering, especially for the compositions with Mn contents less than 1.2 mol%. The evidence of impedance spectroscopy indicated that the concentration of oxygen vacancies decreased significantly by the introduction of O₂ atmosphere. The dielectric loss tanδ was decreased down to 1/2 and the resistivity ρ enhanced 11 times for BF–BT–0 %Mn ceramics by the introduction of O₂ atmosphere. The strains of BF–BT–0.5 %Mn increased from 0.09 to 0.22 and the d ₃₃ ^* increased from 119 to 284 pm/V after sintering in O₂ atmosphere. The Curie temperature and piezoelectric constant of O₂ sintered BF–BT–1.2 %Mn reached up to 500 °C and 353 pm/V, respectively. This work suggests that sintering in the O₂ oxygen atmosphere is an effective way to improve the dielectric and piezoelectric properties of BiFeO₃–BaTiO₃ solid solutions.