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 T-c gradually decreases from 653 to 624 degrees C with increasing the Mn modification. The electrical properties of NKBN-based ceramics are improved significantly by the addition of Mn. The piezoelectric constant d(33), dielectric loss tan delta, mechanical quality factor Q(m) and remanent polarization P-r for the NKBN ceramics with 3.0 mol% MnCO3 modification were found to be 25 pC/N, 0.28%, 2817, 14.50 mu C/cm(2), respectively, together with the high T-c (similar to 643 degrees C) and stable piezoelectric properties, demonstrating that the Mn modified NKBN-based ceramics are the promising candidates for high-temperature applications. (C) 2012 Elsevier B.V. All rights reserved.