Enhancement of energy-storage properties of K0.5Na0.5NbO3 modified Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 lead-free ceramics
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A lead-free ceramics (1 − x)(0.84Na0.5Bi0.5TiO3–0.16K0.5Bi0.5TiO3)–xK0.5Na0.5NbO3 (x = 0, 0.03, 0.06, 0.09, 0.12, 0.15) for energy-storage application have been fabricated by conventional solid state method. All compositions were crystallized into perovskite solid solution structure ascertained by XRD. SEM micrograph revealed that homogeneous grain could be obtained by addition of appropriate K0.5Na0.5NbO3 (KNN). The depolarization temperature (Td) decreased significantly from 140 to 70 °C, while the maximum dielectric constant temperature (Tm) reduced slightly with increasing KNN. And the addition of KNN improved the energy-storage properties significantly by weakening the ferroelectricity of Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 (NBT–KBT) ceramics. When x = 0.09, the highest energy-storage density (W = 1.51 J/cm3) and energy efficiency (η = 65.0 %) were obtained at room temperature. Besides, the temperature stability of energy-storage density could satisfy ΔW/W100°C ≤ ±20 % when the addition of KNN was over 0.09 from 20 to 150 °C.
KeywordsMorphotropic Phase Boundary Remanent Polarization Depolarization Temperature Conventional Solid State Method Breakdown Field Strength
This work was supported by Natural Science Foundation of China (Nos. 51372191, 51102189), International Science and Technology Cooperation Program of China (2011DFA52680), the program for New Century Excellent Talents in University (No. NCET-11-0685), the Key program of Natural Science Foundation of China (No. 50932004) and the Fundamental Research Funds for the Central Universities (WUT: 2014-IV-134).
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