Search

We studied the sintering behavior under reducing conditions of laminates and the performance of the sintered monolithic samples of Li- and Ta-modified sodium potassium niobate (KNNLT) lead-free piezoceramics. Sintering under low p O2 allows co-firing with base metal electrodes, which is an important step towards competitive multilayer actuator fabrication technologies. We present results on phase composition, microstructure and electromechanical properties of KNNLT ceramics, obtained by sintering laminates under low oxygen partial pressure of 10−10 atm at temperatures from 970 °C to 1070 °C and reoxidized at 850 °C with p O2 between 10-9 atm and 10-1 atm. Sintered samples exhibit dense and fine-grained microstructures with low dielectric losses of 2%. A normalized strain coefficient d 33 * = 330 pm/V was obtained at 3 kV/mm for a sample reoxidized at 10-3 atm. Samples reoxidized at very low p O2 exhibit increased dielectric losses and leakage currents at 150 °C as signature of larger oxygen vacancy concentrations. [ABSTRACT FROM AUTHOR]

The sintering behavior, microstructure and permeability of Co/Ti-substituted M-type hexagonal ferrites BaCo x Ti x Fe 12−2 x O 19 (1.0≤ x ≤1.4) was studied for applications as multilayer inductors in the high-frequency range up to 2 GHz. Single-phase M-type ferrites were obtained after calcination at 1000 °C. The saturation magnetization and coercivity decrease with x and hysteresis measurements illustrate a gradual transition of the anisotropy from uniaxial to planar. Addition of 5 wt% of a BBSZ glass allows densification at 900 °C through liquid-phase sintering. The permeability of samples sintered at 900 °C increases with the Co/Ti substitution and reaches its maximum of µ′ =16 at 1 MHz at x =1.3 with a resonance frequency f r ≥1 GHz. Monolithic ferrite multilayer inductors were fabricated with printed Ag coil patterns by co-firing at 900 °C. It is shown that Co/Ti-substituted hexagonal M-type ferrite is an excellent material for the high-frequency multilayer inductors. [ABSTRACT FROM AUTHOR]

The Super-Junction power Metal-Oxide-Semiconductor Field-Effect-Transistor (SJ-MOSFET) is one of the main switches in solar, lighting, consumer, server, and telecom applications. Among other market requirements a long lifetime is crucial, thus device robustness and reliability are decisive in quality assessment. Several failures are attributed to the action of the parasitic Bipolar Junction Transistor (BJT) inherent to the physical structure of the SJ-MOSFET. Our purpose is to gain insight into the role of the parasitic BJT under fast voltage pulse condition and to determine if the Transmission Line Pulse (TLP) can be used as a new method for predicting the Single Event Burnout (SEB) sensitivity of SJ-MOSFETs. SEB is caused by extreme localized triggering of the parasitic BJT while the whole device is in the off-state. However, TLP is uniform across a device and drives it into the avalanche multiplication regime. We demonstrate by direct comparison to equivalent SJ-Diodes that the parasitic BJT stabilizes the SJ-MOSFET when subjected to high voltage pulses generated by a TLP system. We conclude that the fast voltage method is not suited for emulating cosmic ray induced failure, but shows immense potential in analyzing device failure in other regimes. [ABSTRACT FROM AUTHOR]

Room-temperature deposited SiNx passivation of InGaAs/InP heterostructure bipolar transistors (HBTs) with graded base was investigated. The passivation indicated that the surface recombination significantly affected the HBT performances. Both the base current and the base current ideality factor were found to decrease drastically after the SiNx passivation. The passivation also resulted in the increase of the current gain. The ideality factor of the surface recombination current of 2 was identified by the analyses of emitter–base diodes with different sizes. The emitter-size-dependent current gain showed that the improvement was due to the reduction of surface recombination. The SiNx passivation also suppressed the dependence on the perimeter-to-area ratio of the emitter junction. [Copyright &y& Elsevier]

Abstract: This study discusses the complex late Holocene evolution of the Gediz River north of Kula, western Turkey, when a basaltic lava flow dammed and filled this river valley. Age control was obtained using established and novel feldspar luminescence techniques on fluvial sands below and on top of the flow. This dating constrained the age of the lava flow to 3.0–2.6ka. Two damming locations caused by the lava flow have been investigated. The upstream dam caused lake formation and siltation of the upstream Gediz. The downstream dam blocked both the Gediz and a tributary river, the Geren. The associated lake was not silted up because the upstream dam already trapped all the Gediz sediments. Backfillings of the downstream lake are found 1.5km upstream into the Geren valley. The downstream dam breached first, after which the upstream dam breached creating an outburst flood that imbricated boulders of 10m3 size and created an epigenetic gorge. The Gediz has lowered its floodplain level at least 15m since the time of damming, triggering landslides, some of which are active until present. The lower reach of the Geren has experienced fast base level lowering and changed regime from meandering to a straight channel. Complex response to base level change is still ongoing in the Geren and Gediz catchments. These findings are summarized in a diagram conceptualizing lava damming and breaching events. This study demonstrates that one lava flow filling a valley floor can block a river at several locations, leading to different but interrelated fluvial responses of the same river system to the same lava flow. [Copyright &y& Elsevier]