TEM and EDS investigation of heterogeneous interfaces in cofired multilayer ceramic capacitors

Abstract The interfacial microstructure and cofiring migration between Ag Á/Pd electrode and Pb-based relaxor ferroelectric ceramics were directly investigated via transmission electron microscope and energy dispersive X-ray spectroscopy (EDS). Different silver migration abilities of 70Ag Á/30Pd and 90Ag Á/10Pd electrodes were confirmed by EDS microanalysis. This difference is generally considered to be responsible for different effects of inside electrode on the reliability of multilayer cofired devices. Further, Pb diffusion and new phase formation near the interface were detected, incorporating interfacial microstructural observation. A good consistency of direct experimental evidence to the following theoretic analyses was well combined in this paper.

Combining parametric and nonparametric topic model to discover microblog event

Compared with traditional news media, microblog holds overwhelming superiority in fast-diffusion and comprehensive coverage of topics. Microblog becomes an effective, particular and important carrier of affair information and many other text analysis tasks, e.g., event discovering based on microblog have special significance. Common tools of content analysis, such as topic model, however, experience severe data sparsity problems due to short length of microblog. Following previous researchers' idea, such as separating personal interest post from global event post, we further differentiate general topics from event topics and adopt nonparametric method to model the birth and death of event. We conduct experiments on Twitter data set, and the experimental results demonstrate that our method can not only discover event effectively, but also mine higher quality general topics.Computer Science, Information SystemsEngineering, Electrical & ElectronicCPCI-S(ISTP)

Sintering and Electrical Properties of Lead-Free Na0.5K0.5NbO3 Piezoelectric Ceramics

Lead-free Na0.5K0.5NbO3 (NKN) piezoelectric ceramics were fairly well densified at a relatively low temperature under atmospheric conditions. A relative density of 96%–99% can be achieved by either using high-energy attrition milling or adding 1 mol% oxide additives. It is suggested that ultra-fine starting powders by active milling or oxygen vacancies and even liquid phases from B-site oxide additives mainly lead to improved sintering. Not only were dielectric properties influenced by oxide additives, such as the Curie temperature (Tc) and dielectric loss (D), but also the ferroelectricity was modified. A relatively large remanent polarization was produced, ranging from 16 μC/cm2 for pure NKN to 23 μC/cm2 for ZnO-added NKN samples. The following dielectric and piezoelectric properties were obtained: relative permittivity ɛT33/ɛ0=570–650, planar mode electromechanical coupling factor, kp=32%–44%, and piezoelectric strain constant, d33=92–117 pC/N

Transport of zinc ions in the hyporheic zone: Experiments and simulations

Large amounts of toxic metals are discharged into rivers and lakes, but little is known about the factors that drive the adsorption and transformation of these metals in the hyporheic zone and the exchange flux across the sediment-water interface. To better understand transport and transformation of metal ions in the hyporheic zone, flume experiments and numerical simulations were performed in a streambed with periodic bedforms using zinc ions. Compared to non-adsorbing contaminant, the results show that adsorption leads to a more rapid decrease in the concentration of Zn2+ in the overlying water, and a lower final concentration is reached. The mass of adsorbed ions is several times higher than that of free ions in the bedform’s water phase. Indeed, metal adsorption is in the shallow layer of the streambed. Although this prevents heavy metal groundwater contamination, the same cannot be said of shallow layer of the hyporheic zone. Knowledge of the migration and transformation of metal ions in the hyporheic zone provides insights pertinent to the restoration of polluted rivers

Excellent Energy-Storage Performance of (0.85 – <i>x</i>)NaNbO₃–<i>x</i>NaSbO₃–0.15(Na_0.5La_0.5)TiO₃ Antiferroelectric Ceramics through B‑Site Sb⁵⁺ Driven Phase Transition

NaNbO3-based relaxor antiferroelectric (AFE) ceramics are receiving more and more attention for high power pulse applications. A commonly used design strategy is to add complex perovskites with lower tolerance factors. Herein, a new lead-free AFE system of (0.85 – x)NaNbO3–xNaSbO3–0.15(Na0.5La0.5)TiO3 was specially designed considering the substitution of Sb5+ for Nb5+ reduces the polarizability of B-site ions but increases the tolerance factor. The formation of nanodomains with stable AFE orthorhombic R phase symmetry contributes to a slim and double-like polarization-field hysteresis loop, while the increased resistivity and activation energy as a result of sintering aids lead to an enhanced breakdown strength. Therefore, an excellent energy density Wrec ≈ 6.05 J/cm3, a high energy efficiency η ≈ 80.5%, and good charge–discharge performances (power density PD ≈ 155 MW/cm3 and discharging rate t0.9 ≈ 44.6 ns) were achieved in MnO2-doped x = 0.03 ceramics. The experimental results demonstrate that the B-site Sb5+ driven orthorhombic P–R phase transition and increased local structure disorder should provide a new strategy to design high-performance NaNbO3-based relaxor AFE capacitors