Electrical properties and relaxation behavior of Na-doped BaBiNb5O15 ceramics

Abstract

The electrical performance and relaxation behavior of Na + doped BaBiNb 5 O 15 compound were investigated. The grain conductivity of the BaBi 0.96 Na 0.04 Nb 5 O 15-δ compound is 4.71 × 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 BaBi 0.96 Na 0.04 Nb 5 O 15-δ and BaBiNb 5 O 15 sample can reach 1.12 × 10 −4 S/cm and 4.0 × 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 BaBiNb 5 O 15 sample, and E = 0.49 eV for BaBi 0.96 Na 0.04 Nb 5 O 15-δ sample, which indicates that the relaxation activation energy increases with the Bi 3+ ions partially replaced by Na + ions in the BaBiNb 5 O 15 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 BaBi 0.96 Na 0.04 Nb 5 O 15-δ sample. After aging for the different time at 773 K, the excellent thermal stability of the BaBi 0.96 Na 0.04 Nb 5 O 15-δ sample can be found.