ESB Layer Research Articles

A simulation study on electrochemical properties of Bi-layered electrolytes GDC(Gd0.1Ce0.9O1.95)/YSZ(Y0.16Zr0.84O1.92), ESB(Er0.4Bi1.6O3)/GDC and ESB/YSZ with different layer thickness fractions in solid oxide fuel cells

The electrochemical properties of bi-layered electrolytes GDC(Gd0.1Ce0.9O1.95)/YSZ(Y0.16Zr0.84O1.92), ESB(Er0.4Bi1.6O3)/GDC and ESB/YSZ with different layer thickness fractions in the temperature range from 400 to 800 °C have been investigated by simulating calculations based on a charge transport continuity equation and the characteristic conductivity parameters of YSZ, GDC and ESB. It has been found that the model cells with ESB/GDC and ESB/YSZ bi-layered electrolytes can render a higher maximum power density that increases with the ESB layer thickness than those with GDC/YSZ bi-layered electrolytes in the studied temperature range. While the oxygen partial pressure at the interface of ESB/GDC is much lower than that of ESB/YSZ electrolyte with the same ESB thickness fraction, a higher interfacial oxygen partial pressure than the critical decomposition value of Bi2O3 can be achieved in the ESB/YSZ electrolytes even with small YSZ thickness fractions. This result strongly suggests that the ESB/YSZ, instead of ESB/GDC, would be a thermodynamic stable bi-layered electrolyte with high output power density for potential applications in the intermediate to low temperature SOFCs.

In Situ Formation of Er0.4Bi1.6O3 Protective Layer at Cobaltite Cathode/Y2O3-ZrO2 Electrolyte Interface under Solid Oxide Fuel Cell Operation Conditions.

Bismuth-based oxides exhibit outstanding oxygen ionic conductivity and fast oxygen surface kinetics and have shown great potential as a highly active component for electrode materials in solid oxide fuel cells (SOFCs). Herein, a Nb-doped La0.6Sr0.4Co0.2Fe0.7Nb0.1O3-δ (LSCFNb) electrode with 40% Er0.4Bi1.6O3 (ESB) composite electrode was successfully fabricated by decoration method and directly assembled on barrier-layer-free yttrium-stabilized zirconia (YSZ) electrolyte cells, achieving a peak power density of 1.32 W cm-2 and excellent stability at 750 °C and 250 mA cm-2 for 100 h. ESB decoration also significantly reduces the activation energy from 214 kJ mol-1 for the O2 reduction on pristine LSCFNb electrode to 98 kJ mol-1. Further microstructural analysis reveals that there is a redistribution and migration of the ESB phase in the ESB-LSCFNb composite toward the YSZ electrolyte under the influence of cathodic polarization, forming a thin ESB layer at the cathode/YSZ electrolyte interface. The in situ formed ESB layer not only prevents the direct contact and subsequent reaction between segregated SrO and YSZ electrolytes, but also remarkably promotes the oxygen migration/diffusion at the interface for O2 reduction reaction, resulting in a remarkable increase in power output and a decrease in activation energy. The present study clearly demonstrated the in situ formation of a highly functional and active ESB protective layer at LSCFNb cobaltite cathode and YSZ electrolyte interface via ESB-decorated LSCFNb composite cathode under SOFC operation conditions.

Vertical coupling between the mesopause region and sporadic-E layer during equatorial counter electrojet events – A case study

This paper presents a case study exploring the variability of daytime ionospheric sporadic E (Es) during Counter Equatorial Electrojet (CEJ) events over Trivandrum (8.5°N, 77°E, 0.5°N dip lat.), a dip equatorial station in India. It makes use of collocated measurements of (a) daytime mesopause temperature estimated using a Multiwavelength Dayglow Photometer, (b) base height of sporadic E-layer i.e. Esq obtained from a Digital Ionosonde, (c) Equatorial Electrojet (EEJ) induced magnetic field at the surface measured using a Proton Precession Magnetometer and (d) neutral meridional and zonal winds measured using meteor wind radar. The study addresses why, only on certain CEJ days, the Es layer turns into a blanketing Es layer, also referred to as Esb layer, appearing for a brief period and almost simultaneously as the CEJ induced magnetic field on the surface is either zero or very small, and not on all the CEJ days despite the reversal of the zonal winds in the dynamo region (∼98 km). Further, a simulation using the simultaneously measured zonal wind and temperature shows that during CEJ, especially when the zonal wind reverses and the mesopause temperature lowers, the conditions are in fact less favourable for the ionization to converge resulting in Esb. On the other hand, on such occasions, the meridional wind exhibits a tendency to turn equatorward with time with the changeover gradually happening as the altitude decreases. These observations have been discussed to allude to the possible role of the overall wind system and its spatio-temporal changes in the ionospheric altitudes which could influence the gradual transition of Esq to Esb over the dip equator.

High performance cathode-unsintered solid oxide fuel cell enhanced by porous Bi1.6Er0.4O3 (ESB) interlayer

Dense bismuth oxides stabilized with lanthanide dopants (δ-Bi2O3) are always used as interlayer for thin layer GDC (gadolinia-doped ceria) or YSZ (yttria-stabilized zirconia) electrolyte solid oxide fuel cell to improve the cell performance. Dense ESB (Bi1.6Er0.4O3) layer preparation needs special equipment or well synthesized nano-sized powders, which is not friendly for large scale and commercial application. In this paper, anode support unsintered cathode cell with porous ESB interlayer is prepared through simple screen print and its electrochemical performance is tested. No matter sintered or not, porous ESB interlayer lowers both the polarization resistance and ohmic resistance, and enhances cell performance, especially for the ohmic resistance of unsintered cells. The cell with ESB porous interlayer and SSC (Sm0.5Sr0.5CoO3-δ)-ESB unsintered cathode achieves a peak power density of 1.329 W cm−2 at 700 °C, which is 1.61 times higher than that of the cell without ESB interlayer and 0.93 times higher than that of the sintered cell. However, the durability of porous ESB interlayer enhanced cells is not ideal and it should be improved in further works.

The influence of tidal winds in the formation of blanketing sporadic e-layer over equatorial Brazilian region

This work analysis the blanketing sporadic layers (Esb) behavior over São Luís, Brazil (2° 31′ S, 44° 16′ W, dip: −4.80) which is classified as a transition region between equatorial and low-latitude. Hence, some peculiarities can appear as Esb occurrence instead of the common Esq, which is a non-blanketing irregularity layer. The analysis presented here was obtained using a modified version of a theoretical model for the E region (MIRE), which computes the densities of the metallic ions (Fe+ and Mg+) and the densities of the main molecular ions (NO+, O2+, N2+) by solving the continuity and momentum equations for each one of them. In that model, the Es layer physics driven by both diurnal and semidiurnal tidal winds are taken into account and it was extended in height coverage by adding a novel neutral wind model derived from the all-sky meteor radar measurements. Thus, we provide more trustworthy results related to the Es layer formation in the equatorial region. We verified the contribution of each tidal wind component to the Esb layer formation in this equatorial region. Additionally, we compared the Es layer electron density computed by MIRE with the data obtained by using the blanketing frequency parameter (fbEs) deduced from ionograms. The results show that the diurnal component of the tidal wind is more important in the Esb layer formation whereas the semidiurnal component has a little contribution in our simulations. Finally, it was verified that the modified MIRE presented here can be used to study the Esb layers occurrence over the equatorial region in the Brazilian sector.

Competition between winds and electric fields in the formation of blanketing sporadic E layers at equatorial regions

In the present work, we analyze the competition between tidal winds and electric fields in the formation of blanketing sporadic E layers (Esb) over Sao Luis, Brazil (2° 31′ S, 44° 16′ W), a quasi-equatorial station. To investigate this competition, we have used an ionospheric E region model (MIRE) that is able to model the Esb layers taking into account the E region winds and electric fields. The model calculates the densities for the main molecular and metallic ions by solving the continuity and momentum equations for each of the species. Thus, the main purpose of this analysis is to verify the electric fields role in the occurrence or disruption of Esb layers through simulations. The first results of the simulations show that the Esb layer is usually present when only the tidal winds were considered. In addition, when the zonal component of the electric field is introduced in the simulation, the Esb layers do not show significant changes. However, the simulations show the disruption of the Esb layers when the vertical electric field is included. In this study, we present two specific cases in which Esb layers appear during some hours over Sao Luis. We can see that these layers appear when the vertical electric field was weak, which means that the tidal components were more effective during these hours. Therefore, the vertical component of the electric field is the main agent responsible for the Esb layer disruption.

Gd0.1Ce0.9O1.95/Er0.4Bi1.6O3 bilayered electrolytes fabricated by a simple colloidal route using nano-sized Er0.4Bi1.6O3 powders for high performance low temperature solid oxide fuel cells

Thin and dense bilayer electrolytes consisting of erbium stabilized bismuth oxide (ESB) and gadolinium-doped ceria (GDC) were fabricated on tape-cast porous Ni–GDC anode-supports using a scalable and cost-effective colloidal deposition process. Nano-sized ESB particles were successfully synthesized at temperatures as low as ∼500°C using wet chemical co-precipitation. Due to the high sinterability of this powder, dense ESB layers were obtained at a sintering temperature of 800°C. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis of a full button cell with an ESB/GDC bilayer sintered at 800°C showed no visible interfacial diffusion between each layer. A systematic study on the sintering behavior of ESB revealed that at higher sintering temperatures, bismuth oxide can sublime or penetrate into the GDC sublayer. The effect of both the ESB layer and the GDC layer thickness on increasing open circuit potential (OCP) was demonstrated. The current–voltage measurement of the cell showed high power density (∼1.5Wcm−2) at 650°C due to the increase in OCP and a significant reduction in area specific resistance when compared to solid oxide fuel cells (SOFCs) with a single GDC layer. These results demonstrate that ESB/GDC bilayer electrolytes have significant potential for high performance SOFCs at low operational temperature.

Development of High Performance Ceria/Bismuth Oxide Bilayered Electrolyte SOFCs for Lower Temperature Operation

This study examines the development of lower temperature solid oxide fuel cells (SOFCs) and the incremental improvement in performance obtained from a wide range of techniques, from pressed anodes to tape-cast anodes, from gadolinia-doped ceria (GDC) single-layer electrolytes to erbium-stabilized bismuth oxide (ESB)/GDC bilayer, and from -GDC composite cathodes to optimized -ESB composites. GDC single-layer electrolyte-based SOFCs were prepared from four different fabrications and exhibit maximum power densities ranging from 0.338 to at . At each fabrication stage, an ESB layer was applied to form a bilayer electrolyte. ESB was deposited by a range of techniques including colloidal deposition and pulsed laser deposition. The result confirms that depending on a fabrication route, the bilayer electrolyte can reduce the total area specific resistance (ASR) 33–49% and increase the maximum power density 44–93%. By using a combination of the materials and fabrication routes, a maximum power density of and total cell ASR was achieved at for a bilayer cell.

High Performance Ceria/Bismuth Oxide Bilayered Electrolyte IT-SOFC

This study examines the incremental improvement in SOFC performance comprised of components prepared from a wide range of techniques-from pressed anodes to tape-cast anodes, from GDC single-layer electrolytes to ESB/GDC bilayer, and from LSCF-GDC composite cathodes to optimized BRO7-ESB composites. GDC single-layer electrolyte based SOFCs were prepared from two different fabrications and exhibit maximum power densities ranging from 338 to 407 mW/cm2, at 650 {degree sign}C. At each fabrication stage, an ESB layer was applied to form a bilayer electrolyte. ESB was deposited by screen printing and drop coating. The result confirms that depending on a fabrication route the bilayer electrolyte can reduce the total ASR 33~48 % and increase the maximum power density 51~74 %. Using a combination of the materials and fabrication routes, a maximum power density of 808 mW/cm2 and 0.133 total cell ASR was achieved at 650 {degree sign}C for a bilayer cell.

Solar cycle dependent characteristics of the equatorial blanketing E<sub><i>s</i></sub> layers and associated irregularities

Abstract. The occurrence of blanketing type Es (Esb) layers and associated E-region irregularities over the magnetic equatorial location of Trivandrum (8.5° N; 77° E; dip ~0.5°) during the summer solstitial months of May, June, July and August has been investigated in detail for the period 1986–2000 to bring out the variabilities in their characteristics with the solar cycle changes. The study has been made using the ionosonde and magnetometer data of Trivandrum from 1986–2000 along with the available data from the 54.95 MHz VHF backscatter radar at Trivandrum for the period 1995–2000. The appearance of blanketing Es layers during these months is observed to be mostly in association with the occurrence of afternoon Counter Electrojet (CEJ) events. The physical process leading to the occurrence of a CEJ event is mainly controlled by the nature of the prevailing electro dynamical/neutral dynamical conditions before the event. Hence it is natural that the Esb layer characteristics like the frequency of occurrence, onset time, intensity, nature of gradients in its top and bottom sides etc are also affected by the nature of the background electro dynamical /neutral dynamical processes which in turn are strongly controlled by the solar activity changes. The occurrence of Esb layers during the solstitial months is found to show very strong solar activity dependence with the occurrence frequency being very large during the solar minimum years and very low during solar maximum years. The intensity of the VHF radar backscattered signals from the Esb irregularities is observed to be controlled by the relative roles of the direction and magnitude of the prevailing vertical polarization electric field and the vertical electron density gradient of the prevailing Esb layer depending on the phase of the solar cycle. The gradient of the Esb layer shows a more dominant role in the generation of gradient instabilities during solar minimum periods while it is the electric field that has a more dominant role during solar maximum periods.