NaMg 0.12 Nb 0.88 O 3 - x BiYbO 3 (abbreviated as NMN- x BY) ( x = 0, 0.005, 0.01, 0.015, 0.02, 0.04 and 0.08) ceramics were fabricated by using a traditional solid-state reaction method. The crystal structure, morphology, relaxation behavior and energy storage properties of NMN- x BY) ceramics were systematically investigated. X-ray diffraction patterns (XRD) demonstrates that all samples present a single pseudo-cubic phase. It is also found that the grain sizes vary irregular with the BY content, and it can be reduced by the appropriate addition of BY content as indicated by scanning electron morphology. From the measured dielectric properties , it can be seen that all samples are transformed from normal ferroelectric (FEs) to relaxor ferroelectric (RFEs). The maximum relaxor diffuseness coefficient γ (∼1.78) is obtained for 0.98NMN-0.02BY ceramic. As x increases, the polarization-electric ( P - E ) hysteresis loops gradually become slimmer. The largest discharged energy density (∼0.998 J/cm 3 ) and the maximum energy efficiency (∼70%) are obtained at 170 kV/cm for x = 0.04. Meanwhile, the discharge energy densities present relatively excellent temperature stability for x = 0.02 in the temperature range from 20 to 140 °C. This work demonstrates a wide potential application in enhancing the storage properties of lead-free ferroelectric materials by co-doping MgO and bismuth-based perovskites .
Wei Li,Xiang Xia,Jiangtao Zeng,Liaoying Zheng,Guorong Li
NaNbO 3 (NN)-based solid solutions show potential applications in energy storage capacitors, strain actuators, and electrocaloric cooling devices. However, NN ceramics with distinct structures, which are prepared using various Nb 2 O 5 precursors, have not been studied. In this work, two types of Nb 2 O 5 precursors were used, including coexisting orthorhombic and monoclinic phases (denoted as OM), and single orthorhombic phase (denoted as O). Phase structure, grain morphology, sintering characteristics, ferroelectric performance, dielectric properties , and thermal-expansion properties were systematically investigated. Rietveld refinement of XRD data revealed that synthesized and sintered samples showed different phase structures. The content of ferroelectric phase (Q phase, space group P2 1 ma) was 82.7% in synthesized NN-OM, whereas it was only 73.2% in synthesized NN-O; it was 33.8% in sintered NN-OM, while it was 18.6% in sintered NN-O. Raman spectra verified that the Q phase in NN-OM was more than that in NN-O. Curie temperature ( T c ) of NN-OM was 363 °C, whereas T c of NN-O was only 352 °C. Furthermore, compared with NN-O, NN-OM showed an inhomogeneous grain size distribution, lower optimum sintering temperature , higher phase transition temperature, stronger ferroelectric performance, and larger thermal-expansion displacement. Therefore, crystal structure of Nb 2 O 5 has a great influence on the structure and performances of NN ceramics.
危险品化学品经营许可证（带存储）