Dielectric, ferroelectric, and piezoelectric properties of Gd-modified CaBi2Nb2O9 high Curie temperature ceramics

This paper reports the enhanced piezoelectric properties of gadolinium-modified Ca1−xGdxBi2Nb2O9 (CBN-100xGd, where x = 0–0.07) high Curie temperature polycrystalline ferroelectric ceramics. The crystal structure, microstructural morphology, and electrical properties of Gd-modified CBN ceramics are investigated in detail. The results reveal that the Gd-modified CBN ceramics have a pure two-layer Aurivillius-type structure, and exhibit plate-like grains. The resultant Gd-modified CBN ceramics exhibit better piezoelectric and electromechanical properties by comparison with unmodified CBN. The composition of CBN-3Gd exhibits the optimized piezoelectric performance with a high piezoelectric constant d33 value of 13 pC/N and a high Curie temperature Tc of 947 °C. The dc electrical resistivity is significantly enhanced, and that of the CBN-3Gd is 2.45 × 107 Ω cm at 500 °C and 1.53 × 106 Ω cm at 600 °C, which is larger by two orders of magnitude compared with that of unmodified CBN ceramics at the same temperature. Such good electrical properties suggest that the Gd-modified CBN ceramics are promising materials for high-temperature piezoelectric sensor applications.