Papers by Keyword: BNT-BT

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Authors: Ye Jing Dai, Jin Song Pan, Xiao Wen Zhang
Abstract: (Na0.5Bi0.5)TiO3 (BNT) system ceramics are considered to be an excellent candidate for leadfree piezoelectric ceramics. In this paper, (1–x)Na0.5Bi0.5TiO3-xBaTiO3 (x = 0.03 ~ 0.10) was synthesized by conventional mixed-oxide technique. The powders were calcined at 950oC for 2 h and the pressed disks were sintered at 1145oC for 2 h in air atmosphere. The phase structure was investigated by X-ray diffraction technique (XRD). It is revealed that the morphotropic phase boundary (MPB) lies in a narrow composition range of x=0.05–0.08 but not a unique composition (x = 0.055 or 0.06) as shown before [1-4]. The microstructures of the ceramics were investigated by scanning electron microscopic. In addition, the piezoelectric and dielectric properties of this system were also investigated. It was indicated that both the piezoelectric and dielectric properties are better with the compositions lie near the tetragonal phase within the MPB than that whose compositions lie near the rhombohedral phase.
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Authors: Hiroaki Onozuka, Yuuki Kitanaka, Yuji Noguchi, Masaru Miyayama
Abstract: A single crystal of ferroelectric 0.88(Bi,Na)TiO30.12BaTiO3 (BNTBT) solid solution with tetragonal P4mm structure was grown by the top-seeded solution growth (TSSG) method at a high oxygen pressure (PO2) of 0.9 MPa. The crystals grown by the high-PO2 TSSG method exhibited a large remanent polarization (Pr) of 54 μC/cm2, which leads to a spontaneous polarization of 54 μC/cm2. The large Pr compared with that of crystals grown at PO2 = 0.1 MPa is suggested to originate from a low oxygen vacancy concentration for the crystals grown at a higher PO2. The high-PO2 TSSG method was demonstrated to be effective for obtaining BNTBT crystals with superior polarization and piezoelectric properties.
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Authors: Xiao Fang Cheng, Xin Gui Tang, Shao Gong Ju, Yan Ping Jiang, Qiu Xiang Liu
Abstract: The 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (abbreviated to BNT-BT) powder and ceramic was synthesized by sol-gel process. The phase structure and dielectric properties of the ceramics were investigated. The ceramic was sintering at 1000-1100 degree C for 2-4 h in air atmosphere, and the X-ray diffraction (XRD) results revealed that the samples was pure perovskite-type phase. The Curite temperature of BNT-BT ceramics was high up to 348 degree C. The temperature dependence of dielectric permittivity and loss revealed there were two phase transitions, which were from ferroelectric (tetragonal) to anti-ferroelectric (rhombohedral) and anti-ferroelectric to paraelectric (cubic) in BNT-BT ceramics. Diffuse phase transitions were observed in BNT and BNT-BT ceramics and the Curie-Weiss Exponent (CWE) were nearly 2.
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