Dielectric, Ferroelectric, and Strain Study of BNT-BT-BKT Ceramics for Actuator Applications
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https://doi.org/10.1007/s11664-020-08493-0 Ó 2020 The Minerals, Metals & Materials Society
Dielectric, Ferroelectric, and Strain Study of BNT-BT-BKT Ceramics for Actuator Applications M. CHANDRASEKHAR
,1,2,4 Y. GOVINDA REDDY,3 and P. KUMAR1
1.—Department of Physics and Astronomy, National Institute of Technology, Rourkela, Odisha 769008, India. 2.—Department of Physics, CVR College of Engineering (Autonomous), Hyderabad, Telangana 501510, India. 3.—Department of Physics, University College of Science, Osmania University, Hyderabad, India. 4.—e-mail: [email protected]
The 0.88Bi0.5Na0.5TiO3-0.04BaTiO3-0.08Bi0.5K0.5TiO3 (BNT-BT-BKT) ceramics were synthesized by a conventional solid-state reaction, and their structural, dielectric, polarization versus electric field (P–E), and induced strain versus electric field (S–E) properties were studied in detail. The structural study confirmed the morphotropic phase boundary nature of the ceramics. The depolarization temperature (Td) and Curie temperature (Tc) were found to be 70°C and 299°C, respectively, which correspond to ferroelectric to antiferroelectric and antiferroelectric to paraelectric phase transitions, respectively. Remnant polarization (Pr) of 22 lC/cm2, a coercive field (Ec) of 22 kV/cm, and an electric field-induced maximum strain% of 0.63 were observed in the ceramics. As well as good ferroelectric properties, the high induced strain% points to the usefulness of this system for actuator applications. Key words: Actuator, strain, microstructure, thermal analysis
INTRODUCTION Lead (Pb)-based perovskite ferroelectric materials with a morphotropic phase boundary (MPB) have a wide range of applications in transducers, sensors, actuators, and microelectronic devices.1 This is due to their excellent dielectric, piezoelectric, and ferroelectric properties near the MPB.2 The toxicity of Pb and its highly volatile nature, especially during sintering at high temperatures, cause serious environmental concerns and health hazards.3 Therefore, at present, the search is on to identify suitable and effective Pb-free ferroelectric materials to replace Pb-based counterparts.3,4 Pb-based materials show excellent properties due to the stereo-chemical activity of the 6s2 lone pair of Pb ions, which causes structural distortions in the perovskite structure. Bismuth-based compounds also have the same or a larger level of ion off-centering than Pb-based
(Received January 5, 2020; accepted September 16, 2020)
compounds because of the 6s2 lone pair of bismuth ions (Bi3+). This suggests that bismuth-based compounds can be promising materials for replacing Pbbased compounds.5 MPB in a ferroelectric compound separating different phases or symmetries, which lead to an increase in the number of polarization directions and hence excellent dielectric, piezoelectric, and ferroelectric properties.6 On the other hand, binary or ternary composition-based ferroelectric materials are also useful for most of the above-mentioned applications. Therefore, enhancement in the properti
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