An oxygen defect-related dielectric relaxation behaviors of lead-free Ba(HfxTi1−x)O3 ferroelectric ceramics

Abstract

The structure, dielectric, ferroelectric property and high-temperature dielectric relaxation behaviors (HTRBs) were systematically studied for the first time in the Ba(HfxTi1−x)O3 ferroelectric ceramics. It was noted that the TC of the Ba(HfxTi1−x)O3 ceramics decreases, while TO and TR increases with the increase of Hf quantity. Furthermore, the HTRBs were observed in all samples. Mechanisms of HTRBs were studied from complex impedance and ac conductivity, exposing that it was concerned with the drifting of oxygen vacancies (OVAs). Based on the value of theoretical calculation for activation energy, it was concluded that the HTRBs were attributed to the short distance hopping of the OVAs and the conduction was ascribed to the long-range move of doubly-ionized OVAs in Ba(HfxTi1−x)O3 system. Meanwhile, electron paramagnetic resonance spectra were measured to detect the defects in BHTO ceramics. The results showed that the OVAs-related defect signals were observed at g = 1.942. In addition, the dielectric constant peak of relaxation could be significantly restrained by O2 annealing. This further proved that the HTRBs being associated with the defect of oxygen.