Collector Layer Research Articles

Optimization of the Anode Current Collector Layer Thickness for the Cathode-Supported Solid Oxide Fuel Cell

The influence of anode current collector layer (ACCL) thickness is studied for different ACCL porosity and different pitch width. The results shows conclusively that the output current density depends strongly on the ACCL thickness and a suitable choice of the ACCL thickness is very important for the high performance of a SOFC stack. Furthermore, the optimal ACCL thickness is found to be dependent linearly on the pitch width and the parameters for the linearity are given.

Characterization of PCFC‐Electrolytes Deposited by Reactive Magnetron Sputtering; Comparison with Ceramic Bulk Samples

AbstractSrZr0.84Y0.16O3–α (SZY16), BaZr0.84Y0.16O3–α (BZY16), BaCe0.8Zr0.1Y0.1O3–α (BCZY10), and BaCe0.90Y0.10O3–α (BCY10) thin films with the thickness of lower than 6 micron are successfully deposited by reactive magnetron sputtering on alumina substrate covered by about 200 nm Pt3Ti collector layer. The corresponding ceramic bulk samples are prepared by solid state reaction. In order to obtain dense BZY16 and BCZY10 samples, 1 wt.% ZnO was added before sintering process.As deposited films are amorphous and crystallise under the expected crystal structure at different temperatures (e.g., SZY16 ≈ 623 K; BZY16 ≈ 423 K; BCY10 ≈ 873 K, and BCZY10 ≈ 873 K). SZY16 and BZY16 coatings are stable in air with respect to carbonation and hydration. BZY16 coatings require an in situ crystallization in order to avoid further cracking due to the tensile stress generation associated with the crystallization phenomenon, so they are deposited directly onto hot substrate (Tsubstrate ≈ 523 K). BCZY10 amorphous coatings present a good chemical stability against carbonation in air up to 573 K but the coatings decompose in BaCO3 and CeO2 mixture after annealing treatment at around 873 K for 2 h in air, instead of the expected double substituted BaCeO3 perovskite structure. Nevertheless, the crystallization perovskite structure is obtained after annealing treatment under vacuum to prevent the carbonation of the coating. BCY10 requires in situ crystallisation (Tsubstrate ≈ 873 K) to obtain BaCeO3 structure while avoiding the carbonation of the film. All the bulk samples present the perovskite structure with a relative density higher than ∼80% and without trace of ZnO or BaCO3. Eighty percent of relative density was demonstrated to give a good compromise between porosity and grain boundary blocking effects. The electrical properties of the films and pellets are investigated by AC impedance spectroscopy in air. Conductivities of crystallised coatings are close but always significantly lower than those of ceramic bulk samples of the same composition.

Principles of kinetic “Ion” modeling of adsorptive collector layer at the surface of nonferrous heavy metal sulfides

The article considers principles of constructing kinetic models of an adsorptive collector layer at sulfide mineral surface and explains the physics of the models that consists in the connection between ions of flotation slurry liquid phase and relative areas of mineral grain surface.

Polymer Material Dependence in the Polymer/Small Molecule Metal-Base Organic Transistors

A hybrid metal-base organic transistor composed of a vacuum-deposited small-molecule emitter layer and a solution-processed polymer collector layer was fabricated using three types of conductive polymer, poly(3-hexylthiophene) (P3HT), poly(2-methoxy-5(2′-ethyl)hexoxy-phenylenevinylene (MEH-PPV) and poly(9, 9-dioctylfluorene-co-benzothiadiazole) (F8BT). Clear current amplification was observed only in the device with P3HT, and output current density of 12.6 mA/cm2, on/off ratio of 105, and current amplification factor of 76 were achieved at a collector voltage of 5 V and base voltage of 3 V. The output current decreased in order of P3HT > MEH-PPV > F8BT. The relationship between energy levels of polymer materials and carrier transmission process through the base electrode were discussed.

Lattice orientation control of lithium cobalt oxide cathode film for all-solid-state thin film batteries

For the application to all-solid-state thin film batteries, LiCoO2 thin films are deposited by RF-sputtering with controlling the lattice orientations to maximize lithium-ion diffusivity in film textures. The nano-sized crystalline grains grow up with the (003) preferred orientation parallel to the substrates at room temperature due to the lowest surface energy of this atomic plane. However, because the surface energy difference of atomic planes of LiCoO2 reduces with increasing substrate temperature, the influence of surface energy becomes weaker at high temperature. The LiCoO2 thin films with the (110) preferred orientation are obtained at higher temperatures by dominant influence from the lowest the volume strain energy of this orientation. To take advance of this orientation effect in full cell, the influences of the metallic current collector layer on the structural properties of sputtered cathode are investigated. It turns out that the Li2O buffer layers between the cathode films and the metallic current collector layers can suppress the formation of lithium-deficient phase, Co3O4, and the growth of (003) plane by reducing the lattice match between of LiCoO2 plane and Al(111) plane. The LiCoO2 films with the controlled orientation show enhanced rate performance owing to improved interfacial resistance and lithium-ion conductivity.

Electrochemical contribution of silver current collector to oxygen reduction reaction over Ba0.5Sr0.5Co0.8Fe0.2O3−δ electrode on oxygen-ionic conducting electrolyte

Nowadays, there is a doubt about the electrochemical contribution of silver current collector on the oxygen reduction reaction (ORR) over oxide electrodes in SOFCs since many reports have demonstrated that the modification of porous oxide electrodes with nano-size silver can obviously improve the electrocatalytic activity for ORR. In this study, the electrochemical contribution of silver current collector to the performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) electrode on Sm0.2Ce0.8O1.9 (SDC) electrolyte for ORR was specifically investigated. The active layer of BSCF electrode was found to be around 25 μm by using both silver and gold current collectors. Much better performance was demonstrated by using silver current collector, both from symmetric cell and single cell tests. However, EIS of silver on SDC electrolyte demonstrated the silver alone as electrode actually had poor performance for ORR. In addition, SEM-EDX confirmed that there was no silver diffused from the current collector layer to modify the porous BSCF electrode. Interestingly, the activation energy for oxygen reduction over BSCF electrode was reduced by applying silver current collector. We then proposed a mechanism to explain the improved electrochemical performance of BSCF electrode by considering the high activity of silver for oxygen surface diffusion.

Electrochemical Properties of Silver Based Composite Electrodes for SOFC Cathodes and Current Collectors

Performance of the cathode and cathode current collecting layers is of vital importance for development of stable solid oxide fuel cells (SOFCs) during long-term operational conditions. Although pure silver electrodes densify and become impermeable for gas transport at operating temperatures (e.g. 800oC) of SOFCs, incorporation of oxide particles introduces open porosity to silver composites. Previously, it was demonstrated that stable porosity and electrical properties of porous silver composites were achieved at 800oC in air for >5000 hours. Stable open porosity of obtained silver current collectors was utilized to fabricate LSM (lanthanum-strontium manganite), LSF (lanthanum-strontium ferrite), and LSCF (lanthanum-strontium-cobalt ferrite) composites of silver for SOFC cathode applications. Impedance spectroscopy techniques were applied to reveal polarization mechanisms of fabricated cathode/current collector layers. While infiltration of LSM gave rise to the performance of porous silver as cathode, infiltration of LSF and LSCF lowered the cathode polarizations further due to their enhanced ionic conductivities.

$\hbox{GaAs/In}_{0.5}\hbox{Ga}_{0.5}\hbox{P}$ Laser Power Converter With Undercut Mesa for Simultaneous High-Speed Data Detection and DC Electrical Power Generation

We demonstrate novel GaAs/In0.5Ga0.5P high-speed laser power converters (LPCs), which not only can detect the envelope of incoming high-speed optical data but also can efficiently convert its optical dc component to dc electrical power. By utilizing the graded p-type GaAs and n-type In0.5Ga0.5P layers as photoabsorption (P) and collector (C) layers, respectively, the problem of slow-motion holes under 830-nm-optical-wavelength excitation and the conduction-band-offset-induced electron blocking effect between the P/C layers, which seriously limit the high-speed performance of LPC, can both be eliminated. Furthermore, by using the undercut mesa structure of the In0.5Ga0.5P C layer to further reduce the large junction capacitance under forward operation, we can achieve invariable high-speed performance (~9 GHz) from zero to near turn-on voltage (+0.8 V), which corresponds to the operation point of our LPC with the maximum power conversion efficiency (~15%).

Design and Analysis of Ultra-High-Speed Near-Ballistic Uni-Traveling-Carrier Photodiodes Under a 50-$\Omega$ Load for High-Power Performance

We demonstrate a near-ballistic uni-traveling-carrier photodiode (NBUTC-PD) with a scaled-down epi-layer structure designed for high-power performance in the sub-THz frequency regime. Compared with UTC-PDs, NBUTC-PDs offer a higher optimum bias voltage for the near-ballistic transport of electrons, which leads to improvement in the output power performance. Furthermore, a small load resistance ( <; 50 Ω), which would sacrifice the output power for minimizing the output ac voltage swing on dc bias point, is not necessary. By scaling down the collector layer thickness and active area of the NBUTC-PDs, we achieve a large optical-to-electrical bandwidth (250 GHz) and a high saturation current (17 mA), which is close to the theoretical maximum, under a 50-Ω load and -2-V bias.

High Responsivity and High Power UTC and MUTC GaInAs-InP Photodiodes

We have developed a high-performance uni-traveling-carrier (UTC) and a modified uni-traveling-carrier (MUTC) photodiode (PD). We report a comparison between the two devices comprising both a 1.5- μm-thick absorption layer followed by a 0.5-μm-thick transparent collector layer. Both devices showed simultaneously a high responsivity (larger than 0.92 A/W at 1.55 μm), a high saturation current (larger than 100 mA at 10 GHz), and a high linearity (OIP3 of 35 dBm at 10 GHz). Thanks to a partly depleted absorber, the MUTC-PD is demonstrated to achieve a higher bandwidth (more than 20 GHz at high current), while the UTC-PD is demonstrated to achieve a higher saturation current and a less voltage dependent radio-frequency and linearity characteristics.

Silver Based Perovskite Nanocomposites as Combined Cathode and Current Collector Layers for Solid Oxide Fuel Cells

Properties of silver at elevated temperatures limit its use as a porous electrode or current collector in solid oxide fuel cell (SOFC) configurations. Its relatively low melting temperature (962°C) leads to accelerated densification of silver at operating temperatures of intermediate temperature SOFCs (550°C–800°C). In previous studies, powder based silver composites demonstrated stable microstructures with desirable porosity and electrical conductivity during long-term testing. Although the characterized features of the silver based composites allowed their use as efficient and stable cathode current collectors, they demonstrated limited electrochemical performance as a cathode layer. In this study, nanostructured coatings of various perovskite based cathode materials (lanthanum-strontium manganite (LSM), lanthanum-strontium ferrite (LSF), lanthanum-strontium cobalt-ferrite (LSCF)) were deposited into porous silver composites by infiltration of polymeric precursors to enhance their electrode efficiencies. As a result, novel metal-matrix perovskite nanocomposites were obtained. The properties of the Ag based nanocomposites allowed their use as a combined cathode and current collector layer with significantly improved electrochemical performance and long term stability at 800°C in air.

Surface‐light‐emitting transistors based on vertical‐type metal‐base organic transistors

Abstract— Light‐emitting transistors having a metal‐base organic transistor (MBOT) structure demonstrate both the function of an organic thin‐film transistor (OTFT) and organic light‐emitting diode (OLED). The MBOT is a vertical‐type organic transistor having a simple structure composed of organic/metal/organic layers demonstrating high‐current and low‐voltage operation. The light‐emitting MBOT was fabricated simply by inserting additional layers of hole‐transporting and emissive materials used in the OLED into the col lector layer. The device showed perfect surface emission similar to an OLED. A luminance modulation of 370 cd/m2 was observed at a collector voltage of 20 V and a base voltage of 3 V. This device can be applied to an OLED display device to increase the numerical aperture or reduce the required current of the TFT backplane.

The Effect of Humidity and Oxygen Partial Pressure on LSM–YSZ Cathode

AbstractTwo series of anode supported solid oxide fuel cells (SOFC) were prepared, one with a composite cathode layer of lanthanum strontium manganite (LSM) and yttria stabilized zirconia (YSZ) on top and the other further has a LSM current collector layer on top. The fuel cells were heat treated at 1,000 °C in air or nitrogen choosing dry or humid (70% steam) conditions. XRD, SEM, and XPS investigations were performed on the various samples. The most severe modifications were observed in humid nitrogen atmosphere at low oxygen partial pressure. LSM surface change goes along with a decrease of manganese concentration and strontium enrichment on the surface of the materials. Formation of monoclinic zirconia and zirconate phases was also observed. These results give a closer insight into possible degradation mechanisms of SOFC composite cathode materials in dependence of humidity and oxygen partial pressure.

Dynamic Analysis of Cascaded Laser Power Converters for Simultaneous High-Speed Data Detection and Optical-to-Electrical DC Power Generation

We analyze the dynamic behaviors of a novel device, i.e., cascaded high-speed laser power converters (LPCs), which can detect the direct-current (dc) component of an incoming high-speed optical data stream and efficiently convert its dc component to dc electrical power. By utilizing a p-type photoabsorption layer in our LPC, the problem of slow-motion holes can be eliminated, and only the electrons act as the active carriers. We can thus achieve high-speed performance with the LPC under forward-bias operation with a small electric field inside. Furthermore, according to our modeling and measurement results, there are a significant alternating-current capacitance reduction and an electron-trapping effect at the interface between the absorption and collector layers with a significant degradation in the carrier drift velocity. These become more serious with the increase in optical pumping power and forward-bias voltage and truly limit the net optical-to-electrical (O-E) bandwidth of the device. In order to overcome such a transient-time-limited bandwidth and further increase the maximum dc output voltage of the LPC, we connect two single LPCs in series (cascade). Error-free data detection of 10-Gb/s and an O-E dc power-generation efficiency of 21.1% can be achieved simultaneously at a wavelength of 850 nm by the use of such two cascaded LPCs.

Fabrication of Ni-YSZ anode supported tubular SOFC through iso-pressing and co-firing route

In the present work, a co-pressing and co-firing process has been developed to fabricate thin YSZ electrolyte film over tubular NiO-YSZ anode support for solid oxide fuel cell (SOFC) application. The one-end-closed tubular anode support was fabricated by cold isostatic pressing (CIP) and electrolyte coating was made by dip coating a terpineol based YSZ slurry over the anode support. The anode support along with coated electrolyte layer was co-pressed in CIP and co-fired at 1350 °C to get impervious electrolyte layer. LSM-YSZ composite cathode layer and LSM cathode current collector layer was formed by dip coating terpineol based slurries followed by sintering at 1150 °C. Symmetric cells in planar configuration were fabricated and tested by electrochemical impedance spectroscopy (EIS) in order to determine area-specific resistance (ASR) for electrode polarization. An ASR value of 0.79 Ω cm2 was obtained for Ni-YSZ|YSZ interface at 900 °C in humidified H2. The ASR value was 0.55 Ω cm2 for LSM-YSZ|YSZ interface at 900 °C in air. Tubular single cell having ∼1 cm2 cathode current collecting area was generated and the cell was found to give a maximum of 62 mW cm−2 power density when tested at 900 °C. The interfacial microstructures and electrochemical test results illustrate the feasibility of fabrication of tubular anode supported SOFC by co-pressing and co-firing.

InP/GaAsSb DHBTs With 500-GHz Maximum Oscillation Frequency

We report the realization of 0.3-μm emitter InP/GaAsSb/InP DHBTs with cutoff frequencies <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> = 365 GHz and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> = 501 GHz. Our devices were implemented with a 15-nm C-doped graded base and a 125-nm InP collector and feature a peak current gain β = 35, with a base sheet resistance <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SH</sub> = 1160 Ω/sq. The present transistors are the first InP/GaAsSb DHBTs to feature <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> = 500 GHz, according to three extraction schemes. The present transistor performance is limited by an undepleted collector layer associated with a doping tail extending from the subcollector.

Performance of (La,Sr)(Co,Fe)O 3− x double-layer cathode films for intermediate temperature solid oxide fuel cell

In this study the performance evaluation of (La,Sr)(Co,Fe)O 3− x (LSCF) double-layer films characterized by impedance spectroscopy between 403 and 603 °C to be used for intermediate temperature solid oxide fuel cells (IT-SOFCs) is presented. Two LSCF layers with different microstructures were sequentially deposited onto Ce 0.9Gd 0.1O 1.95 (CGO) substrates in a symmetrical fashion. A first layer of La 0.6Sr 0.4Co 0.2Fe 0.8O 3− x with a thickness of 7 μm and a nano-scaled particle size was deposited by electrostatic spray deposition (ESD) technique. Different deposition conditions were used in preparing the ESD films to evaluate the influence of film morphology on the electrochemical performance. After annealing, a current collector layer of La 0.58Sr 0.4Co 0.2Fe 0.8O 3− x with ∼45 μm in thickness and a larger particle size was deposited by screen printing. Area specific resistances ( ASRs) were determined from impedance spectroscopy measurements performed in air between 403 and 603 °C, at 25 °C steps. A dependence of electrochemical performance on the morphology of the LSCF layer deposited by ESD was observed. The lowest ASR, measured during 130 h of isothermal dwelling at 603 °C, averaged 0.13 Ω cm 2 with negligible variation and is the lowest reported value for this composition, to the best of our knowledge. Reported results assure an excellent suitability of this type of assembly for IT-SOFCs.

Efficient Cathodes for Solid Oxide Fuel Cells Prepared by Polymeric Precursor Infiltration

A novel technique based on polymeric precursor infiltration into porous layers was developed to process composite materials as highly efficient cathode/current collector structures for solid oxide fuel cells (SOFCs). Powder based Pt and YSZ inks were used to form porous cathode/current collector layers on electrolyte supported symmetrical structures that were infiltrated with polymeric LSM precursor. Electrochemical testing of the samples was performed by impedance spectroscopy techniques. Polarization resistance of the cathode was as low as 0.022 Ohm.cm2 at 800°C demonstrating the potential of fabricating highly efficient cathodes. Infiltration process led to a stable composite of the cathode/current collector structures, ensuring a high current collection efficiency and long term stability at operational temperatures.

Fabrication of InP/InGaAs DHBTs with Buried SiO2 Wires

In this paper, we report the fabrication and device characteristics of InP/InGaAs double heterojunction bipolar transistors (DHBTs) with buried SiO 2 wires. The SiO 2 wires were buried in the collector and subcollector layers by metalorganic chemical vapor deposition toward reduction of the base-collector capacitance under the base electrode. A current gain of 22 was obtained at an emitter current density of 1.25 MA/cm 2 for a DHBT with an emitter width of 400 nm. The DC characteristics of DHBTs with buried SiO 2 wires were the same as those of DHBTs without buried SiO 2 wires on the same substrate. A current gain cutoff frequency (f T ) of 213 GHz and a maximum oscillation frequency (f max ) of 100 GHz were obtained at an emitter current density of 725 kA/cm 2 .

Design principles of selective collecting agents

On the ground of the flotation theory requirements to composition of a collector layer adsorbed at the surface of minerals under flotation and depressing, the regularities of the effect exerted by intra-molecular and inter-molecular interactions on physicochemical properties of collectors, the selectivity conditions of the relationship between the functional group of a collector and crystal lattice elements of a mineral, as well as the demands for physical sorption form of collectors, the article couches and validates design principles for selective collecting agents.