Enhancement in lithium storage performances of SiO2/graphene-based nanocomposites prepared by low cost and facile approach

Journal of Materials Science: Materials in Electronics - The new nanocomposites of silicon dioxide/reduced graphene oxide (SiO2/rGO) and silicon dioxide/nitrogen-doped reduced graphene oxide...     

Phase,microstructure and ferroelectric properties of new complex-structured ferroelectric ceramics in the PZT–SBN system

This study aimed to fabricate and characterize new complex-structured ceramics with formula (1-x)Pb(Zr_0.52Ti_0.48)O₃–xSrBi₂Nb₂O₉ or (1-x)PZT–xSBN (where x=0, 0.1, 0.3 and 0.5 weight fraction). The ceramics were prepared by a solid-state mixed-oxide method and sintered at temperatures between 1000 and 1250 °C. Optimum sintering temperature for this system was found to be 1050 °C for 3 h dwell time. X-ray diffraction patterns of (1-x)PZT–xSBN powders showed peak intensities of two-phase mixture corresponding to the relative amount of each phase as a result of SBN addition. Microstructure of (1-x)PZT–xSBN ceramics showed a variation in grain shape and grain size. The small addition of SBN (x=0.1) was also found to improve ferroelectric properties of pure PZT ceramic.     

Orthorhombic-tetragonal phase transition induced by Ta isovalent doping and its effect on the fatigue characteristics of KNL-NSTx ceramics

The effect of Ta addition on the bipolar fatigue characteristics of lead-free KNL-NST_x ceramics (x = 0, 0.04, 0.07 and 0.11 mol%) is studied. Bipolar cycling up to 1 × 10⁶ cycles leads to strong degradation of the polarization in unmodified KNL-NS ceramics. This can be explained by the development of strong domain wall pinning, leading to the build-up of high local stresses and consequently microcracking of the material. The addition of Ta reduces the domain wall pinning effect and improves the bipolar fatigue resistance. In order to understand the fatigue mechanism, a model based on oxygen vacancy accumulation is proposed. This model is expected to guide future fatigue studies that are concerned with novel lead-free KNN-based materials.     

Dielectric properties,electric-field-induced polarization and strain behavior of Lead Zirconate Titanate-Strontium bismuth Niobate ceramics

The dielectric properties and electric-field-induced polarization and strain behavior of (1-x)PZT-xSBN (x ranged from 0 to 1.0 weight fraction) ceramics prepared by a conventional mixed-oxide method were investigated. The dielectric properties indicated that the dielectric constant of PZT could be enhanced with small addition of SBN (x = 0.1). From the polarization hysteresis loop measurements, it was found that the ferroelectric properties of nominal PZT-SBN ceramics changed strongly from the normal ferroelectric in PZT-rich ceramics to the paraelectric character in SBN-rich compositions. The strain hysteresis loops of nominal PZT-SBN under bipolar electric field loading suggested that the butterfly curve was observed in some compositions (0 ≤ x ≤ 0.3 and pure SBN ceramic). This research clearly showed the significance of SBN in controlling the electrical properties of nominal PZT-SBN ceramics.     

Ferroelectric fatigue mechanism under bipolar electrical loading in KNN lead free piezoelectric ceramic

The effect of bipolar cyclic electrical loading on the ferroelectric and piezoelectric properties of KNN ceramics is investigated. The results showed that the bipolar fatigue leads to a decrease in domain switchability and piezoelectric responses of the ceramic. In the early period of cyclic loading, the fatigue mechanism is dominated by the domain wall pinning effect. When the number of fatigue cycles increases, the microstructural damage has a large impact on the fatigue process. From this, a qualitative model based on the relationship between domain pinning mechanism and internal stress is proposed.     

Structure–property relations of ferroelectric BaTiO3 ceramics containing nano-sized Si3N4 particulates

Barium titanate/silicon nitride (BaTiO₃/xSi₃N₄) powder (when x = 0, 0.1, 0.5, 1 and 3 wt%) were prepared by solid-state mixed-oxide method and sintered at 1400 °C for 2 h. X-ray diffraction result suggested that tetragonality (c/a) of the BaTiO₃/xSi₃N₄ ceramics increased with increasing content of Si₃N₄. Density and grain size of BaTiO₃/xSi₃N₄ ceramic were found to increase for small addition (i.e. 0.1 and 0.5 wt%) of Si₃N₄ mainly due to the presence of liquid phase during sintering. BaTiO₃ ceramics containing such amount of Si₃N₄ also showed improved dielectric and ferroelectric properties.