Reduced dielectric loss and enhanced piezoelectric properties of Mn modified 0.71BiFeO_3-0.29BaTiO_3 ceramics sintered under oxygen atmosphere

摘要

0.71BiFeO_3-0.29BaTiO_3 piezoelectric ceramics with Mn modification (BF-BT-x %Mn) sintered in air and 02 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 O_2 sintered ceramics possessed larger grain sizes and more homogeneous distribution. Dielectric, ferroelectric and piezoelec'tric properties of BF-BT-xMn ceramics were improved obviously after O_2 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 O_2 atmosphere. The dielectric loss tanδ was decreased down to 1/2 and the resistivity p enhanced 11 times for BF-BT-0 %Mn ceramics by the introduction of O_2 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 O_2 atmosphere. The Curie temperature and piezoelectric constant of O_2 sintered BF-BT-1.2 %Mn reached up to 500 ℃ and 353 pm/V, respectively. This work suggests that sintering in the O_2 oxygen atmosphere is an effective way to improve the dielectric and piezoelectric properties of BiFeO_3-BaTiO_3 solid solutions.