Electrical Properties of Textured Bismuth Layer-Structured Ferroelectric Ceramics with Large Number of Layers (m = 5)

Abstract

Bismuth layer-structured ferroelectrics (BLSF) ceramics are attractive materials for high temperature sensor applications, because of their high Curie temperature Tc (300–900 °C), and the large anisotropy of their electromechanical coupling factor kt/kp or k33/k31. In this study, BLSF ceramics with a large number of layers, namely, (K0.5Bi0.5)2Bi4Ti5O18 + MnCO3 0.3 wt%+ Bi2O3 0.025 wt% (KBT5) and Sr0.75Ca0.25Na0.5Bi4.5Ti5O18 + CeO2 1 wt% [(SC)NBT5] ceramics, were prepared by ordinary firing (OF) and hot forging (HF) methods, and their electrical and piezoelectric properties were examined. Both KBT5 and (SC) NBT5 ceramics showed high Tc values of 545 and 424 °C, respectively. The OF-KBT5 ceramic had an electromechanical coupling factor k33 of 0.14 and a piezoelectric constant d33 of 20 pC/N, whereas the HF-KBT5 ceramic had k33 of 0.17 and d33 of 31 pC/N. On the other hand, the OF-(SC) NBT5 ceramic had k33 of 0.13 and d33 of 17 pC/N, whereas the HF-(SC) NBT5 ceramic had k33 that increased to 0.32 and d33 to 41 pC/N. The k33 and d33 of the HF ceramics were improved compared with those of the OF ceramics. Thus, the KBT5 and (SC) NBT5 ceramics with oriented grains were shown to have good piezoelectric properties with high Tc.