Electrical properties and relaxation behavior of Na-doped BaBiNb5O15 ceramics

The electrical performance and relaxation behavior of Na+ doped BaBiNb5O15 compound were investigated. The grain conductivity of the BaBi0.96Na0.04Nb5O15-delta compound is 4.71 x 10(-5) S/cm at 763 K, which is an order of magnitude lower than the parent sample at the same measuring temperature. The highest total conductivity of the BaRi(0.96)Na(0.04)NbsO(15-delta) and BaBiNb5O15 sample can reach 1.12 x 10(-4) S/cm and 4.0 x 10(-5) S/cm at 643 K, respectively, which indicates that the slight Na+ doping can improve the total conductivity. A dielectric relaxation peak related to thermal activation was observed. The activation energy values are E = 0.47 eV for BaBiNb5O15 sample, and E = 0.49 eV for BaBi(0. 96)Na(0.04)Nb(5)O(15-delta )sample, which indicates that the relaxation activation energy increases with the Bi3+ ions partially replaced by Na+ ions in the BaBiNb5O15 compound. In addition, the oxygen relaxation peak position shifts to the low-frequency direction, which indicates that Na+ ions doping causes the decrease of oxygen vacancy mobility. The lower oxygen vacancy mobility results in the lower grain conductivity in the BaBi0.96Na0.04Nb5O15-delta sample. After aging for the different time at 773 K, the excellent thermal stability of the BaBi0.96Na0.04Nb5O15-delta sample can be found.