The application of lead-free dielectric ceramics for energy storage has received extensive attention because of their remarkable potential as pulse capacitors in power electronic devices. The current study developed a strategy for improving the energy storage performance of (K 0.5 Na 0.5 )NbO 3 (KNN)-based ceramics by incorporating Bi(Zn 2/3 Nb 1/3 )O 3 to reduce grain size, increase dielectric breakdown strength, and enhance ferroelectric relaxation degree. The resulting 0.87KNN–0.13BZN ceramics exhibited a high energy density (7.4 J/cm 3 ) and moderate energy efficiency (74%) at an ultrahigh electric field (750 kV/cm) as well as excellent optical properties. Therefore, the 0.87KNN–0.13BZN ceramic is a promising candidate for pulse capacitors, providing a feasible approach for the development of new lead-free energy storage materials.
Bi 1.5 Zn 1.0 Nb 1.5 O 7 (BZN) thin films are synthesized on a FTO (Fluorine -doped SnO 2 transparent conductive glass) substrate by an improved sol-gel method. The pH of the precursor is controlled by citric acid and ammonia, and the effect of pH on the crystal structure and electrical properties of the BZN films is studied. When the precursor pH is 5, the relative intensity of the diffraction peak of BZN films is the highest, the FWHM is the narrowest, and the crystallization degree is the highest, compared to those of BZN films synthesized from precursors at other pH, the crystallization energy offset of the element binding energy of the thin films is the smallest and the phase difference of the binding energy is the closest to the theoretical value, and the films have excellent electrical properties with permittivity of 120, loss tangent of 0.003, tunability of 14.8%, breakdown voltage of 0.43 MV/cm and energy storage density of 9.82 × 10 −2 J/cm 3 .
Xueqing Lei,Helei Dong,Mengyu Yuan,Hongyu Peng,Xinwei Guo,Siyu Liang,Qiulin Tan
s In this work, Bi-Zn-Nb base cubic pyrochlore with A 2 B 2 O 7 structure was purposefully trimmed to make Zn ions in the A site slightly deviate from stoichiometric ratios, and non-stoichiometric (Bi 1.5 Zn 0.5+x )(Zn 0.5 Nb 1.5 )O 7.0+x (BZN, -0.15 ≤ x ≤ 0.05) thin films were fabricated on FTO (fluorine-doped tin oxide) electrodes using the sol-gel process. The structural characterization results confirmed that the phase structure of the BZN films remained cubic pyrochlore after little composition shift. It was found that proper reduction of Zn content can optimize the performance of BZN films, and thin film with a composition corresponding to x = -0.1 demonstrated optimal crystallinity and superior dielectric properties. More specifically, this film exhibited a high tunability of 19.26% (1.17 MV/cm), relatively low loss tangent of 0.0089, and a large figure of merit of 21.6. Furthermore, by introducing the semiconductor FTO as the bottom electrode, the coefficient of the dielectric nonlinearity β for the sol-gel BZN film has been optimized, which is 180% of higher than that of on metal Pt electrode. The excellent properties are attributed to the combination effect of the intrinsic tuning characteristic of non-stoichiometric BZN cubic pyrochlore and the surface electric field effect in Metal Insulator Semiconductor (MIS) structure. This research provides a promising approach to boost the performance of functional thin film electronic devices.
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