Effects of B-site Co2O3 doping on microstructure and electrical properties of Na0.25K0.25Bi2.5Nb2O9 ceramics

The effects of cobalt addition on the properties of Na0.25K0.25Bi2.5Nb2O9 (NKBN)-based ceramics have been investigated in details. It was found that the ceramics possess a pure phase of bismuth oxide layer-type structure. The Curie temperature Tc gradually increases from 653 °C to 662 °C with increasing the Co modification. The electrical properties of NKBN-based ceramics are improved significantly by the addition of Co. The piezoelectric constant d33, dielectric loss tan δ, mechanical quality factor Qm and remanent polarization Pr for the NKBN ceramics with 0.20 wt% Co2O3 modification were found to be 23 pC/N, 0.35%, 3028, 12.03 μC/cm2, respectively. Thermal annealing studies indicated that the cobalt-modified NKBN ceramics system possesses stable piezoelectric properties, demonstrating that the cobalt-modified NKBN-based ceramics are the promising candidates for high-temperature applications.