Microstructure and electrical properties of Mn-modified bismuth-layer Na0.25K0.25Bi2.5Nb2O9 Ceramics

Bismuth layer-structured ferroelectric ceramics Na0.25K0.25Bi2.5Nb2O9+xmol% MnCO3 (NKBN–Mn) were synthesized by a traditional solid-state reaction. The effects of Mn addition on the microstructure and electrical properties of 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 decreases from 653 to 624 °C with increasing the Mn modification. The electrical properties of NKBN-based ceramics are improved significantly by the addition of Mn. The piezoelectric constant d33, dielectric loss tan δ, mechanical quality factor Qm and remanent polarization Pr for the NKBN ceramics with 3.0 mol% MnCO3 modification were found to be 25 pC/N, 0.28%, 2817, 14.50 μC/cm2, respectively, together with the high Tc (∼643 °C) and stable piezoelectric properties, demonstrating that the Mn modified NKBN-based ceramics are the promising candidates for high-temperature applications.

► In this work, Mn-modified Na0.25K0.25Bi2.5Nb2O9 ceramics were prepared by a traditional solid-state reaction.
► Mn ions entered into the Na0.25K0.25Bi2.5Nb2O9 lattices to form a solid solution.
► The electrical properties of NKBN-based ceramics are improved significantly by the addition of Mn.
► The optimized properties of the ceramics: d33 = 25 pC/N, Qm = 2817, Pr = 14.50 μC/cm2, Tc = 643 °C.