High-Temperature Dielectric and Relaxation Behavior of Tantalum-Doped Sodium Bismuth Titanate-Barium Titanate Ceramics
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https://doi.org/10.1007/s11664-020-08441-y 2020 The Minerals, Metals & Materials Society
High-Temperature Dielectric and Relaxation Behavior of Tantalum-Doped Sodium Bismuth Titanate-Barium Titanate Ceramics XIAFENG HE,1 FEIFEI HAN,1 MIN LIU,2 ZHI YUAN,3 XINYU JIANG,1 CHANGZHENG HU,1 SHAOKAI REN,1 XIUYUN LEI,1 and LAIJUN LIU 1,4,5 1.—Guangxi Key Lab of Optical and Electronic Functional Materials and Devices, College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, China. 2.—Institute of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013, China. 3.—Collage of Energy and Building Environment, Guilin University of Aerospace Technology, Guilin 541005, China. 4.—Present address: Guilin University of Aerospace Technology, Guilin 541000, Guangxi, China. 5.—e-mail: [email protected]
Ta-doped 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 [(1 x)(0.94BNT–0.06BT) xTa (x = 0.00–0.02)] ceramics were prepared by a solid-state reaction process. Xray diffraction (XRD) shows a rhombohedral symmetry with space group R3c for all samples. The introduction of Ta moves the low-temperature dielectric anomaly to lower temperature while the high-temperature dielectric anomaly becomes broader, although the dielectric permittivity is depressed slightly. Dielectric permittivity (er) as a function of temperature for the sample x = 0.02 shows a stable and broad relative permittivity 3500 from 50 C to 400 C with low dielectric loss (tand) £ 0.02 from 80 C to 340 C (at 1 kHz). A Debyelike relaxation was found in the paraelectric region. The activation energy of relaxation frequency (Ea) of the samples x = 0, 0.005, 0.01, 0.02 is 0.62 eV, 0.84 eV, 1.15 eV and 1.20 eV and the activation energy of conduction (Econ) is 0.56 eV, 0.72 eV, 0.89 eV and 0.90 eV for x = 0.00, x = 0.005, x = 0.01 and x = 0.02, respectively, which are derived from isothermal impedance spectroscopy and admittance spectroscopy, respectively. The dielectric relaxation behavior is related to the migration of oxygen vacancies and cation vacancies dependence on the concentration of Ta. Key words: High-temperature capacitor, Bi0.5Na0.5TiO3, debye relaxation, oxygen vacancy, cation vacancy
INTRODUCTION Multilayer ceramic capacitors (MLCCs) are in great demand particularly in the electronics industry due to their excellent performance and ability to withstand harsh conditions.1,2 Pb(Zr1 xTix)O3 (PZT) can be widely applied in MLCC devices due to their low dielectric loss and high stable permittivity.3–6 However, Pb may cause serious
(Received May 26, 2020; accepted August 20, 2020)
environmental problems and damage to human health. Therefore, it is of great importance to study environment-friendly materials to take the place of the lead-based materials. The Electronics Industries Alliance (EIA) characterizes X7R/X8R/X9R dielectrics as a ‘‘temperature stable’’ material (X represents the minimum temperature of 55C, while R symbolizes percentage of the capacitance variation limit ± 15% in the whole temperature range, DC
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