Oxygen-vacancy-induced reversible control of ferroelectric polarization in Ba4Eu2Fe2Nb8O30 ceramics

Ba4Eu2Fe2Nb8O30 ceramics with a tetragonal tungsten bronze structure were synthesized under different sintering and annealing conditions. The maximum polarization of air-sintered samples decreased from 4.0 mu C/cm(2) to 3.6 mu C/cm(2) after annealing in an oxygen atmosphere. In contrast, the maximum polarization of oxygen-sintered samples improved from 3.5 mu C/cm(2) to 7.0 mu C/cm(2) after annealing in a nitrogen atmosphere. A reversible enhancement of remanent polarization (0.2 mu C/cm(2)) induced by oxygen vacancies was also detected by the positive up negative down method. This reversible control of ferroelectric polarization was assumed to be associated with the structure modulation induced by oxygen vacancies. To prove this, selected area electron diffraction patterns were studied. The results showed that the oxygen vacancies would influence the direction of O-octahedral tilting and promote the commensurate modulation in Ba4Eu2Fe2Nb8O30, which contributed to the enhanced ferroelectric properties. Published by AIP Publishing.