Effects of Rare Earth Doping on the Electrical and Electromechanical Properties of Lead-Free Bi0.487Na0.427K0.060Ba0.026TiO3 Ceramics

• Published in: 2019 IEEE International Symposium on Applications of Ferroelectrics (ISAF) pp. 1 - 4
• Main Authors: Gozuacik, Namik Kemal, Mensur-Alkoy, Ebru, Alkoy, Sedat
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01-07-2019
• Subjects: BNKBT ceramics; Ceramics; Dielectrics; Doping; Electric fields; electrical properties; Lead; rare-earth doping; Strain; Temperature measurement
• ISSN: 2375-0448
• DOI: 10.1109/ISAF43169.2019.9034931

In this study, the effect of 1.0 mole% Ce, Nd, and Gd doping on the dielectric, ferroelectric, and electromechanical properties of the bismuth sodium potassium barium titanate - BNKBT (Bi 0.487 Na 0.427 K 0.060 Ba 0.026 TiO 3 ) lead-free ceramics have been studied in detail and compared with the undoped BNKBT samples. Ceramic samples have been synthesized by the conventional solid-state reaction method. XRD patterns revealed that all the BNKBT ceramic compositions show pure single perovskite phase. All of the BNKBT ceramics exhibited a dispersive dielectric behavior. The dielectric constant of undoped BNKBT ceramic was measured as 744 at 100 kHz at room temperature. The Curie temperature (T c ) at 100 kHz was determined as 343°C. The dielectric constants were measured as 1249, 1326, and 1067 at 100 kHz at room temperature for Ce, Nd, and Gd doping, respectively. The Curie temperature (T c ) at 100 kHz was determined as 343°C, 340°C, and 346°C, respectively. Addition of 1.0 mole% Ce, Nd, and Gd changed the polarization vs. electric field behavior of undoped BNKBT ceramic from a ferroelectric to an antiferroelectric character at room temperature. Maximum polarizations under 65 kV/cm applied electric field were measured as 40 μC/cm 2 , 35 μC/cm 2 , and 35 μC/cm 2 and remnant polarizations were measured as 8.4 μC/cm 2 , 6.7 μC/cm 2 , and 12.3 μC/cm 2 for Ce, Nd, and Gd doping, respectively, whereas these properties were measured as 39 μC/cm 2 , and 33.1 μC/cm 2 for undoped BNKBT. A large electric field-induced strain of 0.35%, 0.24%, and 0.23% was obtained under an electric field of 65 kV/cm as a result of field-induced phase change between antiferroelectric and ferroelectric phases, whereas the field-induced strain arising from piezoelectric effect in undoped BNKBT was 0.18%, with a piezoelectric coefficient (d 33 ) of 165 pC/N. These results indicate that the BNKBT ceramics can be utilized in high energy density capacitor applications, as well as digital actuator applications.