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221.
(K0.5Na0.5)NbO3 (KNN) based lead free ceramics have been fabricated by a solid state reaction. In this work, LiSbO3 (LS) modified KNN based ceramics were sintered at atmospheric pressure and high density (>96% theoretical) was obtained. The detailed elastic, dielectric, piezoelectric and electromechanical properties were characterized by using the resonance technique combined with the ultrasonic method. The full set of material constants for the obtained polycrystalline ceramics were determined and compared to the pure hot pressed KNN counterpart. KNN-LS polycrystalline ceramic was found to have higher elastic compliance, dielectric permittivity and piezoelectric strain coefficients, but lower mechanical quality factor, when compared to pure KNN, exhibiting a “softening” behavior. However, a high coercive field (∼17 kV/cm) was found for the LS modified KNN material. The properties as a function of temperature were determined in the range of −50-250 °C, showing a polymorphic phase transition near room temperature, giving rise to improved piezoelectric behavior. 相似文献
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Zhu G Wu G Xu X Ji X 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,82(1):74-78
A detailed study was explored to compare the transient absorption spectra of the neat 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) with its solution in water or acetonitrile. It was concluded that the excited triplet state 3[bmim]+* was produced after 266 nm laser irradiation, and then the neutral radical [bmim] and the cation radical [bmim] 2+ were formed through two possible paths. The transient absorption spectra of the neat [bmim][BF4] and its solution were similar but the reaction kinetics were different due to their different local structures such as dimeric or cluster. The energy transfer between excited [bmim][BF4] and β-carotene further affirmed the existence of 3[bmim]+*. And the reaction that the hydrated electron captured by [bmim]+ to produce [bmim] in solution was observed. 相似文献
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Dr. Shuyu Zhou Yuxuan Sun Tong Gao Junhong Liao Prof. Shixi Zhao Prof. Guozhong Cao 《Angewandte Chemie (International ed. in English)》2023,62(42):e202311930
Cation-disordered Rocksalt oxides (DRXs) are a promising new class of cathode materials for Li-ion batteries due to their natural abundance, low cost and great electrochemical performance. High entropy strategy in Mn-based DRXs appears to be an effective strategy for improving the rate capability, but it suffers from challenges including capacity degradation. The present paper reports a new group of high entropy DRXs (HE DRX) based on Ni2+-Nb5+ pair; the structural and chemical evolution upon cycling of DRXs with an increasing transition metal (TM) species are systematically investigated. An explanation is proposed for how the crystal field stability energy determines that HE DRX could exist in single Rocksalt solid solution structures. We further reveal that the charge compensation mechanism in HE DRX is the result of various TM synergistic effect. More importantly, through various in situ and ex situ techniques and theoretical calculation, the effective integration of more TM cation species within the HE DRX framework promotes better Li+ diffusion and improves lattice oxygen stability, consequently increasing capacity upon cycling. 相似文献