Browsing by Author "Xu, Mengxing"

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    Electrocaloric effect in La-doped BNT-6BT relaxor ferroelectric ceramics
    (Elsevier, 2017-09-22) Li, Lucheng; Xu, Mengxing; Zhang, Qi; Chen, Ping; Wang, Ningzhang; Xiong, Dingkang; Peng, Biaolin; Liu, Laijun
    Relaxor [(Bi1/2Na1/2)0.94Ba0.06](1-1.5x)LaxTiO3 (x = 0, 0.03, 0.06, 0.09) ceramics (La-doped BNT-6BT) with composition close to the morphotropic phase boundary (MPB) were successfully prepared by using the conventional solid state reaction method. All samples present almost a pure perovskite phase with the coexistence of tetragonal and rhombohedral. With the increase of La doping content, the degree of the dielectric relaxor dispersion around the dielectric peak which is close to the room temperature increases, and also the transition temperature of ferroelectric-to-relaxor (TF-R) shifts 120 K towards a lower temperature at x = 0.09. The maximum value of the temperature change (ΔT) of the electrocaloric (EC) effect decreases sharply from 1.1 K at x = 0–0.064 K at x = 0.09. A large positive EC effect (maximum ΔT ~ 0.44 K) in a broad temperature range (~ 90 K) close to room temperature is achieved at x = 0.03, indicating that it is a promising lead-free material for application in solid state cooling system. Moreover, it is found that the Maxwell relationship can be well used to assess the EC effects of the La-doped BNT-6BT ceramics when the operating temperature is higher than that of the TF-R, indicating that these relaxor ceramics would perform as an ergodic.
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    Enhanced energy storage performance of (1-x)(BCT-BMT)-xBFO lead-free relaxor ferroelectric ceramics in a broad temperature range
    (Elsevier, 2019-03-03) Xu, Mengxing; Peng, Biaolin; Zhu, Jinian; Liu, Laijun; Sun, Wenhong; Leighton, Glenn J. T.; Shaw, Christopher; Luo, Nengneng; Zhang, Qi
    Relaxor ferroelectrics with high energy storage performances are very attractive for modern applications in electronic devices and systems. Here, it is demonstrated that large energy densities (0.52e0.58 J/cm3) simultaneously with high efficiencies (76è2%) and thermal stabilities (the minimum variation of efficiency < 4% from 323 K to 423 K at x ¼ 0.04) have been achieved in the (1-x)(BCT-BMT)-xBFO lead-free relaxor ferroelectric ceramics prepared using a conventional solid-state reaction method. Large dielectric breakdown strengths and great relaxor dispersion around the dielectric peaks are responsible for the excellent energy storage performances. The energy storage performances of as-prepared ceramics at high BFO doping amount (x ¼ 0.06 and 0.07) were deteriorated seriously due to low dielectric breakdown strengths. However, they could be greatly improved when aged, since the operable electric field was significantly enhanced from 10 kV/cm of as-prepared samples to 100 kV/cm of aged samples due to the reduced concentration of oxygen vacancies during the aging process. The excellent energy storage performances may make them attractive materials for applications in modern energy storage systems in a broad temperature range.