Microstructure and Electrical Properties of Bi_0.47Na_0.47Ba_0.06Cu_0.015Ti_0.985O₃ Ceramics Sintered in Different Atmospheres

Bi_0.47Na_0.47Ba_0.06Cu_0.015Ti_0.985O₃ (BNBCT) lead-free piezoelectric ceramics were prepared by using the solid-state reaction technique. Samples were sintered at 1090 ℃ for 2 h in oxygen (BNBCT-O₂), air (BNBCT-Air), and nitrogen (BNBCT-N₂). Effects of sintering atmospheres on structure and electrical properties of the BNBCT ceramics were thoroughly studied. X-ray diffraction (XRD) results revealed that all samples exhibited pure perovskite phase. XRD Rietveld refinements confirmed that the BNBCT-O₂ ceramics have strong lattice distortion. According to complex impedance spectra, the electrical response activation energy, activation energy of conductivity, and O1s X-ray photoelectron spectra (XPS), it is indicated that oxygen vacancy concentrations are different in different sintering atmosphere. When the oxygen content in sintering atmospheres is sufficiently high, oxygen vacancies can be easily inhibited. Compared with BNBCT-Air and BNBCT-N₂, the BNBCT-O₂ exhibited the highest piezoelectric coefficient (d₃₃=227 pC·N^-1) and the largest remnant polarization (P_r=31.9 μC·cm^-2). It is therefore concluded that the microstructure and electrical properties of BNBCT were related to oxygen vacancy concentration, which could be controlled by the sintering atmosphere. This work provides a feasible way to improve the piezoelectric properties of Bi_0.47Na_0.47Ba_0.06TiO₃-based ceramics by simply controlling the sintering atmosphere.