Effect of oxygen partial pressure during sintering on electric properties of BiFeO₃-based piezoelectric ceramics

The effects of oxygen partial pressure (pO₂) during sintering and post-annealing treatment on the microstructure and electrical properties of Mn-added 0.3BaTiO₃0.1Bi(Mg₁/₂Ti₁/₂)O₃0.6BiFeO₃ ceramics were investigated. The ceramics sintered at pO₂ of 0.11 atm showed pinched polarizationelectric field (PE) loops, while the ceramics sintered in nitrogen gas could not be measured due to dielectric breakdown. By annealed at 800°C for 5 h and cooled slowly, the ceramics showed increased remanent polarizations although their PE loops were still pinched. When the as-sintered ceramics were annealed at 800°C for 5 h and then quenched into water, well-developed ferroelectric hysteresis loops were observed. These results were discussed with grain size and defect dipoles consisted of oxygen vacancies and bismuth vacancies or iron ions with a different valence.