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Sex expression contributes to fruit quality and yield in the Cucurbitaceae. In melon, orchestrated regulation by sex determination genes explains the mechanism of sex expression, resulting in a great variety of sexual morphologies. In this study, we examined the Japanese weedy melon UT1, which does not follow the reported model of sex expression. We conducted QTL analysis using F2plants for flower sex on the main stem and the lateral branch and mapped a “femaleness” locus on Chr. 3 (Fem3.1) and a “type of flower femaleness” (female or bisexual) locus on Chr. 8 (tff8.1).Fem3.1included the known sex determination geneCmACS11. Sequence comparison ofCmACS11between parental lines revealed three nonsynonymous SNPs. A CAPS marker developed from one of the SNPs was closely linked to femaleness in two F2populations with different genetic backgrounds. The femaleness allele was dominant in F1lines from crosses between UT1 and diverse cultivars and breeding lines. This study suggests that the identity oftff8.1isCmCPR5, a recently reported bisexual flower control gene. We found that the Japanese weedy melon UT1 does not follow the conventional sex expression model because of the interaction of the lociFem3.1andtff8.1with the previously reported sex determination genes. The results of this study provide new insights into the molecular mechanisms of sex determination in melons and considerations for the application of femaleness in melon breeding.Key messageJapanese weedy melon exhibits unique sex expression with interactions between previously reported sex determination genes and two novel loci.

A LA-ICP-MS based analytical method for the evaluation of trace PGE leaching.

A self-powered system with a long lifetime would represent an opportunity in the development of a next-generation, standalone Internet of Things. Ceramic capacitors are promising candidates for energy storage components because of their stability and fast charge/discharge capabilities. However, even the energy density of state-of-the-art capacitors needs to be increased markedly for this application. Improving the breakdown electric field represents a potential solution, but operations at such high fields relying on unchanged dielectric permittivity sacrifice the lifetime of the capacitor to some degree. Here, we report ferrorestorable polarization engineering capable of more than doubling the effective permittivity. Our experiments and ab initio calculations demonstrate that a defect dipole composed of Cu3+ and oxygen vacancy in a prototypical ferroelectric BaTiO3 ceramic is coupled with spontaneous polarization. The resultant ferrorestorable polarization delivers an extraordinarily large effective relative permittivity, beyond 7000, with a high energy efficiency up to 89%. Our work paves the way to realizing efficient ceramic capacitors for self-powered applications.

For efficient energy conversion and energy storage, developing highly efficient hydrogen permeable membranes is a crucial issue. Ceramic hydrogen permeable membranes, i.e., protonic electronic mixed conductors, work on bipolar transport of protons and electrons. Ceramic composite membranes meet this requirement with chemical and thermal stability, and they can be used not only as hydrogen permeable membranes but also as electrolytes in protonic ceramic fuel cells (PCFCs). Although improvement in protonic conductivity at heterointerfaces between constituting materials and/or space-charge relaxation around the resistive grain boundaries can be possible origins of the enhanced hydrogen permeability in the composite electrolyte membranes, its detailed mechanisms have not been clarified yet and the strategy of material design for composite membranes has not been established. In this study, the transport properties of composite electrolyte membranes consisting of protonic conductors and electronic conductors are investigated to realize highly efficient PCFC operating at low temperatures and to clarify the principles of carrier transport in the composite membranes. For the protonic conductor and the electronic conductor, we selected La2Ce2O7 (LDC) with a fluorite structure and La0.3Sr0.6TiO3 (LST) with a perovskite structure, respectively. The composite membrane composed of LDC and LST (LDC/LST) with various LDC to LST ratios was prepared by a solid-state reaction. Phase stability of LDC and LST were investigated by X-ray diffraction (XRD) measurements. Transport properties of hydrogen permeation cells using the LDC-LST composite membranes with Pt electrodes were assessed by electrochemical impedance spectroscopy (EIS) measurements and hydrogen permeation measurements. Hydrogen fluxes were measured by gas chromatography. The EIS measurements revealed that the grain-boundary resistance was reduced for the LDC/LST composite membrane in comparison with an LDC membrane. In particular, LDC/LST (weight ratio 1:2) showed the smallest grain-boundary resistance of 26 Ω cm at 600°C under 1%H2/Ar among the measured samples. Besides, the hydrogen permeation measurement showed that LDC/LST exhibited higher hydrogen permeability than the LDC membrane. In addition, the hydrogen flux of LDC/LST (1:2) was almost twice as high as that of LDC at 600°C. The low grain-boundary resistance and the high hydrogen permeability of LDC/LST composite membrane suggests that the introduction of LST accelerates the proton conduction in the membrane.

The electrochemical promotion of ammonia formation on Fe-based electrode catalysts is investigated using proton-conducting-electrolyte-supported cells of H2–Ar, Pt|BaCe0.9Y0.1O3 (BCY)| Fe-based catalysts, H2–N2 at temperatures between 550 °C and 600 °C, and ambient pressure. To clarify the reaction mechanism, the ammonia formation rate is examined using two cathodes: (I) a porous pure Fe electrode with a shorter triple phase boundary (TPB) length and (II) a cermet electrode consisting of Fe–BCY (or W–Fe–BCY) with a longer TPB length. Using the different electrode structures, we investigate the effects of cathodic polarization, hydrogen partial pressure, and electrode materials. The porous pure Fe electrode shows better performance than the Fe–BCY cermet electrode, which suggests that the ammonia formation is accelerated by the electrochemical promotion of catalysis (EPOC) effect on the Fe surface rather than the charge-transfer reaction at the TPB. The electrochemical promotion is governed by a dissociative mechanism, i.e., acceleration of direct N2 bond dissociation with cathodic polarization on the Fe surface, with a smaller contribution by a proton-assisted associative mechanism at the TPB. These findings indicate that the porous pure Fe electrode is more effective for ammonia formation than the (W–)Fe–BCY cermet electrode. Despite the relatively short TPB length, the porous pure Fe cathode achieves a very high ammonia formation rate of 1.4 × 10−8 mol cm−2 s−1 (450 μg h−1 mg−1) under appropriate conditions. This significant result suggests that the effective double layer spreads widely on the Fe electrode surface. Using the identified reaction mechanism, we discuss key processes for improving ammonia formation.

The mechanism of electrochemical promotion of ammonia formation was investigated by kinetic and deuterium isotope analyses using a cell with a Pt (anode)|BaCe0.9Y0.1O3 (BCY)|Fe (cathode) configuration on the introduction of a gaseous mixture of H2(D2)–N2 to the cathode at 550 °C. To clarify the mechanism of electrochemical ammonia synthesis, the reaction orders for hydrogen, α, and nitrogen, β, were investigated. The values of α and β did not change after applying a negative voltage, which indicates that the reaction mechanism at rest potential is the same as that with cathodic polarization. Furthermore, deuterium isotope analysis was conducted to investigate the mechanism of electrochemical promotion. The isotopic composition of ammonia (i.e., NH3−xDx) formed in the cathode was determined using Fourier-transform infrared spectroscopy (FTIR). The results show that the ammonia products with cathodic polarization correspond to the species of H2 (or D2) in the cathode, that is, NH3 (or ND3) was mainly formed when H2 (or D2) was introduced to the cathode. Isotopic analysis revealed that the ammonia formation rate via the electrochemical promotion of catalysis (EPOC) is faster than that via the charge-transfer reaction, suggesting that a significant increase in the ammonia formation rate will be caused by the EPOC.

Colletotrichum orbiculare is a hemibiotrophic fungal pathogen that causes anthracnose disease in cucumber (Cucumis sativus L.) and other cucurbit crops. The cucumber accession Ban Kyuri (G100) has a high level of resistance to anthracnose and is considered to be promising breeding material. Here, we report genetic mapping of loci from this cultivar that confer resistance to 104-T and CcM-1 of C. orbiculare that belong to pathogenic races 0 and 1, respectively. Quantitative trait locus (QTL) analysis based on phenotypic data from 196 F2:3 families detected one major QTL, An5, and one minor QTL, An6.2, for resistance to race 0, and one major QTL, An2, and three minor QTLs (An1.1, An1.2 and An6.1) for resistance to race 1. We identified lysM domain receptor-like kinase 3 (CsaV3_5G036150) and wall-associated receptor kinase-like (CsaV3_6G048820) as candidate genes for An5 and An6.2, respectively. Multiple genes encoding pattern recognition receptors were located in the regions of the QTLs conferring resistance to race 1. Thus, we identified potential sources of genetic resistance to different pathogenic races of C. orbiculare in the Ban Kyuri cultivar of cucumber.Key messageQuantitative trait locus analysis identified independent novel loci in cucumber responsible for resistance to races 0 and 1 of the anthracnose fungal pathogen Colletotrichum orbiculare.

We examined students’ initial and concluding attitudes toward statistics based on course delivery methods. Students enrolled in either traditional or online undergraduate statistics courses (N = 196) completed the Survey of Attitudes Toward Statistics-36. At the beginning of the semester, students in traditional courses felt better about the course and believed it would be easier, compared to students taking statistics online. Attitude differences, however, were mitigated as traditional courses were forced online by the pandemic, and distinct attitudinal differences were not observed at the semester’s end. With limited offerings and restrictions on the delivery of traditional courses in the COVID-19 era, statistics educators should be cognizant of student attitudes, their potential for change, and how to best influence positive attitude shifts for different instructional formats.

The performance of an anode-supported proton-conducting solid oxide fuel cell (p-SOFC) was investigated by controlling transport properties of thin electrolyte membranes. Hole conductivity in electrolyte, which induces to degrade the cell performance, was sufficiently suppressed by using lanthanum tungstate La28-xW4+xO54+3x/2v2-3x/2 (LWO) with high proton conductivity and low hole conductivity. SrFe0.95Nb0.05O3-δ (SFN) and Ni-Ce0.9Gd0.1O2-δ (Ni-GDC10) cermet were used as the cathode and anode, respectively. GDC10 was also used as an interlayer to prevent chemical reactions between the electrolyte and electrodes. SEM images and electrochemical impedance spectroscopy showed that the boundaries between the electrolyte and electrodes were stable because GDC10 blocked chemical reactions and cation diffusion at the electrolyte-electrode interfaces. Fuel cell tests were also performed with SFN/GDC10/LWO/GDC10/Ni-GDC anode-supported single cells. The thickness of the LWO thin electrolyte was approximately 3 μm. The OCV values were measured to be 0.88 V and 0.94 V at 800 °C and 600 °C, respectively. Moreover, the evaluation of the leakage current indicated that thin LWO could achieve the low leakage current due to transport properties such as high proton conductivity and low hole and electron conductivities.

Solid oxide fuel cells (SOFCs) with proton-conducting solid electrolyte, instead of the oxide-ion conducting solid electrolyte have attracted attentions because of their high potential to reduce operating temperatures and to enhance the electrical efficiencies of SOFCs. In addition, the proton-conducting SOFCs with multistage electrochemical oxidation configuration will be promising technology for critically-high electric efficiencies. However, it is known that there are non-negligible charge -carriers other than protons in typical proton-conducting solid oxide electrolytes at relatively high temperatures. The existence of the partial conductivities of holes and/or electrons will cause the internal leakage current that consumes fuel but never generates any electrical power output. The higher ratio of the leakage current to external current will more deteriorate the electrical efficiency. In this study, the effects of blocking -layers formed on the air side surface of base electrolyte layer consisting of BaZr0.8Y0.2O3-δ (BZY82) for suppressing the leakage current have been investigated by using electrochemical parameters of the partial conduction of the materials. The chemical potential profile and leakage current showed large dependence on the material of the blocking -layer. Lanthanum tungstate was found to play a role as unique and strong blocking -layer against the leakage current.

Ferroelectric (Bi0.5K0.5)TiO3–BiFeO3 solid solutions are promising materials for high-temperature piezoelectric applications because of their high depolarization temperature. In this study, we demonstrate the successful growth of high-quality (Bi0.5K0.5)TiO3–BiFeO3 single crystals near the morphotropic phase boundary by a flux method. Crystal growth at a high oxygen pressure of 0.9 MPa drastically reduces leakage currents, which enables ferroelectric polarization switching and a piezoelectric response associated with a rotation of polar nanosized domains. This study contributes to further detailed analyses of the relationship between crystal structures and ferroelectric properties of the (Bi0.5K0.5)TiO3–BiFeO3 solid-solution system.

Density functional theory calculations are conducted for tetragonal BiFeO3–BaTiO3 superlattices to investigate the influence of electronic structures on ferroelectric spontaneous polarization (P s). When the number of the perovskite unit cells in one layer (N) is decreased below 10, the P s starts to decrease from the volume-averaged one (50.9 μC cm−2) and eventually becomes half at N = 1. In the BiFeO3 cell (N = ∞) with a large P s (73.3 μC cm−2), a covalent bond arising from a Bi_6p-O_2p orbital interaction is extended through a Bi–O network and stereo-chemical lone-pair electrons of Bi are accommodated in the opposite direction of the polar c axis. In the superlattice with N = 1, the Bi–O network cannot be developed by the presence of Ba, and then the Bi–O bond becomes ionic. We show that the large P s of the BiFeO3 cell originates from the Bi_6p-O_2p mixing superimposed on the stereo-chemical nature of the lone-pair electrons of Bi.

Highly efficient carriers are developed for hydrogen production by methane cracking with carbon-dioxide activation in a chemical looping system. The carrier materials comprise BaZr0.9Y0.1O3−δ (BZY) with a high proton conductivity and Fe as a base metal, and they are prepared by doping Fe into BZY. Thermal gravimetric analysis (TGA) showed that Fe-doped BZY (BaZr0.9−xFexY0.1O3−δ, BZFY) with x = 0.4 (BZFY40) exhibited a high activity for carbon deposition with methane thermal decomposition. Surface observation and kinetic analysis suggested that the high activity for carbon deposition results from the promotion of tubular carbon growth with growth-mode transition from horizontal to vertical direction for the tubular carbon on reduced BZFY40. The rapid growth of carbon tubes proceeded with the base-growth mechanism, which can provide an advantage in the stable cycle reactions. The carbon removal reaction with carbon dioxide was also investigated. In BZFY, the removal reaction was completed in ~10 min. BZFY reacted with carbon dioxide under carbon dioxide flow to generate barium carbonate. From the BZFY surface observation before and after the reactions, the BZFY plate that was mechanically broken during the carbon deposition and removal cycles could be repaired by filling cracks with carbonate in the BZFY that was generated via the reduction reaction with methane. Therefore, carbon removal from the BZFY surface with carbon dioxide contributes to maintaining the BZFY particle shape during cycles with the self-healing scheme. The BZFY40 carrier has a high activity and durability for the carbon deposition and removal cycle and provides an effective system design for carbon dioxide-free hydrogen generation.

Photoferroelectrics offer unique opportunities to explore light energy conversion based on their polarization-driven carrier separation and above-bandgap voltages. The problem associated with the wide bandgap of ferroelectric oxides, i.e., the vanishingly small photoresponse under visible light, has been overcome partly by bandgap tuning, but the narrowing of the bandgap is, in principle, accompanied by a substantial loss of ferroelectric polarization. In this article, we report an approach, ‘gap-state’ engineering, to produce photoferroelectrics, in which defect states within the bandgap act as a scaffold for photogeneration. Our first-principles calculations and single-domain thin-film experiments of BiFeO3 demonstrate that gap states half-filled with electrons can enhance not only photocurrents but also photovoltages over a broad photon-energy range that is different from intermediate bands in present semiconductor-based solar cells. Our approach opens a promising route to the material design of visible-light-active ferroelectrics without sacrificing spontaneous polarization., Overcoming the optical transparency of wide bandgap of ferroelectric oxides by narrowing its bandgap tends to result in a loss of polarization. By utilizing defect states within the bandgap, Matsuo et al. report visible-light-active ferroelectrics without sacrificing polarization.

Controlling and manipulating defects in materials provides an extra degree of freedom not only for enhancing physical properties but also for introducing additional functionalities. In ferroelectric oxides, an accumulation of point defects at specific boundaries often deteriorates a polarization-switching capability, but on the one hand, delivers interface-driven phenomena. At present, it remains challenging to control oxygen vacancies at will to achieve a desirable defect structure. Here, we report a practical route to designing oxygen-vacancy distributions by exploiting the interaction with transition-metal dopants. Our thin-film experiments combined with ab-initio theoretical calculations for BiFeO3 demonstrate that isovalent dopants such as Mn3+ with a partly or fully electron-occupied eg state can trap oxygen vacancies, leading to a robust polarization switching. Our approach to controlling oxygen vacancy distributions by harnessing the vacancy-trapping capability of isovalent transition-metal cations will realize the full potential of switchable polarization in ferroelectric perovskite oxides.

Proton-conducting oxides have attracted much attention in recent years due to their good ion conductivity at intermediate temperatures (500-700°C), as opposed to conventional oxide ion-conducting oxides that require high temperatures (usually, >900°C). Lowering the operating temperature of reversible protonic ceramic electrochemical cells (RePCECs) is desirable as it reduces material, heating, and insulation costs, while also increasing the operating life of the cell. Nevertheless, along with the desired proton conductivity, typical proton-conducting solid electrolytes also allow the transport of other charged defects like oxygen-vacancies, electrons, and electron holes. The presence of these other defects, especially the electron holes, causes leakage current that significantly reduces the cell’s electrical efficiency. Therefore, an electrolyte capable of reducing leakage current is necessary. Unfortunately, there is usually a trade-off between high ionic conductivity and low hole conduction. For example, while lanthanum tungstate (LWO) has a low electron conductivity and is capable of suppressing hole conduction below 800°C, its proton conductivity is lower than that of commonly used perovskite materials like yttria-doped barium cerate (BCY) or yttria-doped barium zirconate (BZY). Nonetheless, previous studies showed that LWO67 can act as a leakage current-blocking layer when deposited on a BZY82 base electrolyte and the estimated leakage current was almost 200 times lower than that of a BZY82 single layer electrolyte under open-circuit conditions. This suggests that under certain operating conditions, bilayer electrolytes can achieve better performance when compared to their corresponding single-layer electrolytes. Therefore, in this study, we design proton-conducting bilayer electrolytes by investigating the incorporation and transport of charged defects using a steady-state Nernst-Planck-Poisson (NPP) model. The main goals of this work are twofold. Firstly, to find the combination of electrolytes that better suppresses leakage current. For this purpose, we calculate the defect concentration, flux, and electrostatic profiles inside common materials like BCY, BZY, BZCYYb, BZCY, LWO, and different combinations of bilayer electrolytes to better understand how the addition of a leakage current-blocking layer affects proton conduction and overall efficiency. We consider three mobile defects when solving the NPP equation, protons (OHO •), oxygen vacancies (vO ••), and electron holes that are treated as small polarons localized at oxygen sites (OO •). Afterward, the I-V curve and relevant theoretical efficiency are predicted within and A cm-2 (fuel cell and electrolyzer operation) at 500, 600 and 700°C, in order to identify the most promising one. Secondly, to design a cell by finding the optimal thickness of the better performing bilayer electrolyte that maximizes efficiency.

A single crystal of Fe (0.3%)-doped BaTiO3 was grown by a top-seeded solution growth method, and the photovoltaic (PV) properties (at 3.1 eV) in a multi-domain state with a 90° domain structure are investigated. We show that the overall behavior can be well understood by an analytical expression of the domain wall (DW)-PV effect superimposed on the bulk-PV effect. The fitting of photocurrents as a function of light polarization reveals that the offset component of the DW-PV effect is much larger than that of the bulk-PV effect, even though the volume fraction of the DW region is extremely small. A local electric field in the DW region is estimated to be several hundred kV cm−1, which is three orders of magnitude higher than the effective field inside the domains.

Introduction Renewable and clean energies have attracted much interest in recent years due to environmental and economic concerns related to the use of fossil fuels. For this reason, solar and wind energies have become popular alternatives and are widely used in many countries as reliable energy sources. However, these technologies are intermittent by nature which makes it challenging to successfully integrate them into power grids. Reversible electrochemical cells provide an attractive way to store solar and wind energy surplus by operating as an electrolysis cell to produce hydrogen that can be later used to generate electricity by operating as a fuel cell. Reversible cells using proton conductive solid oxide electrolytes have some advantages over other technologies, for instance, they show higher ionic conductivity in the intermediate temperature range which lowers the need for heating. Nonetheless, previous studies show low faradaic efficiencies (FEs) that are usually between 20 and 70%, which means that less than 70% of the applied current is used to produce hydrogen. A state-of-the-art reversible cell by Choi et al [1]. in 2019 yielded a remarkable current density of -1.8 A cm-2 at 600°C and 1.3 V, but the reported faradaic efficiencies ranged from 40 to 75%. In a recent study BCZYYb+1.0wt% NiO electrolyte was used to obtain one of the highest reported faradaic efficiencies to date, between 90-98%. According to the authors, “low faradaic efficiencies can be almost entirely attributed to higher current leakage” [2]. Therefore, an electrolyte capable of considerably reducing leakage current is necessary. Lanthanum tungstate (LWO) is a promising electrolyte material since it has a good ionic conductivity, low electron conductivity and it is capable of suppressing hole conduction below 800°C [3]. In this study, we assess the performance of a solid oxide reversible cell using LWO and other common electrolyte materials like BCY10, BZY20 and BZCYYb1711. Methods The performances for LWO67 and other commonly used electrolyte materials were predicted based on their transport properties using Choudhury’s model [4] with the required conductivity parameters obtained by fitting to reported experimental data (Table 1). Power efficiencies (PEs) were computed for fuel cell operation and faradaic efficiencies for electrolysis cell operation. Additionally, the performances of LWO67/BCY10 electrolyte-supported-platinum (Pt)-symmetric cells were also evaluated using a fuel cell testing unit with an in-line gas chromatograph (GC) to measure the produced hydrogen. A potentiostat/galvanostat was used to measure the characteristic I-V curves and electrochemical impedance. Both the predictions and experiments were performed with a gas composition of 20% O2 in Ar (3% H2O) for the air electrode side and 1% H2 in Ar (3% H2O) for the hydrogen side. Pt was chosen as both the fuel and air electrode to be able to easily compare the efficiencies of LWO67 and BCY10 under the exact same conditions. This is because LWO can react with other electrodes and a thin protective layer would be necessary to prevent this from happening. Results and discussion According to the predictions, LWO67 exhibits the highest PE in fuel cell operation at typical operating conditions of current p-SOFC systems (Fig. 1). In the same way, LWO67 shows the highest faradaic efficiency in electrolysis operation (Fig. 2) exceeding that of BZCYYb by more than 10%. These results are due to LWO67’s low electron and hole conductivities and they suggest that it has great potential as an electrolyte for reversible cells. It was also found that the optimum electrolyte thickness is around 10 µm and lower values produce a decrease in the FE. This occurs because as ionic conductivity increases with decreasing thickness, so does the leakage current. Therefore, there is a trade-off relationship between the electrolyte thickness, the current density, and the efficiency. Moreover, the FEs measured experimentally were higher for LWO67. For example, at 650°C the FE was 26% for BCY10 while it was 37% for LWO67. Nevertheless, this difference is expected to be even higher in anode-supported cells with thinner electrolytes, indicating that LWO67 has potential as an electrolyte material. Additionally, it has been shown that poor electrode performance can affect the FE. Thus, a more active electrode should improve the performance. References [1] S. Choi, T.C. Davenport, S.M. Haile, Energy Environ. Sci. 12 (2019) 206–215. [2] C. Duan et al., Nat. Energy 4 (2019) 230–240. [3] G. Kojo, R. Tsukimura, J. Otomo, Solid State Ion. 306 (2017) 89–96. [4] N.S. Choudhury, J.W. Patterson, J. Electrochem. Soc. 118 (1971) 1398–1403. Figure 1

For efficient operation of proton ceramic fuel cell (PCFC), transport properties of hole and electron are important factors to be controlled as well as that of protons. Ba-based perovskite-type proton conductors have been used as typical electrolytes for the PCFCs because of their high proton conductivity. However, they also exhibit apparent hole conduction under oxidative atmospheres which causes leakage current through the electrolyte. The leakage current leads to not only a decrease in cell voltages but also a reduction of the energy efficiency since the leakage current cannot be utilized as electric power while hydrogen is consumed to generate protons and electrons. Therefore, a novel approach to suppress the leakage current has been required. Lanthanum tungstate (La28−x W4+x O54+3/2x ; LWO) with a high La/W ratio of 6.7 is one of the attractive proton conductors with a quite low hole conductivity. Though its proton conductivity is lower than the typical perovskite-type electrolytes, a high protonic transport number is attractive as a hole blocking layer for the PCFCs. An introduction of a thin LWO hole blocking layer on the Ba-based proton conductors with the high proton conductivity will suppress the leakage current by changing a profile of oxygen chemical potential in the electrolytes as we have proposed previously (Y. Matsuzaki et al., ECS Trans. 91, 1009-1018 (2019)). In this study, we explored the influence of the LWO hole blocking layer on the cell performances of PCFCs by theoretical calculations and experiments. In the theoretical calculations, a BZY|LWO bilayer cell model in which the LWO layer was located at the cathode side was employed. The calculations suggested that the bilayer structure not only improves efficiency but also gives flexibility to control the cell performance as required. Moreover, we experimentally investigated the performance of anode-supported cells with a BZY monolayer electrolyte and with a BZY|LWO bilayer electrolyte to elucidate the effect of the LWO layer. An LWO layer thickness (L LWO) dependence of the OCV in the BZY|LWO bilayer model was calculated based on the transport properties of BZY and LWO. Dependences of the energy efficiency and the power density with respect to a ratio of to a total electrolyte thickness (L total) of 10 μm were calculated for the model at a fixed external current density (I ext) of 250 mA/cm2 and at a fixed terminal voltage (V T) of 1.05 V, respectively. ε was defined by ε = V T I ext/V th I ion, where V th and I ion are a Nernst voltage and an ionic current density. We assumed the following operation conditions; operation temperature of 600 °C, 3% H2O + 97% H2 for anode gas, and 3% H2O + 19.4% O2 + 77.6 % Ar for cathode gas. In the experiments, a BZY monolayer electrolyte and a BZY|LWO bilayer electrolyte were prepared on NiO-BZY cermet substrates by the pulsed-laser deposition (PLD). La0.6Sr0.4Co0.2Fe0.8O3− d (LSCF) cathode was applied for both the cells. To suppress chemical reactions of LWO with BZY and LSCF, thin La-doped ceria (LDC) layers were introduced. The resulted structure of the monolayer cell and the bilayer cell were Ni-BZY|BZY(3.5 μm)|LSCF and Ni-BZY|BZY(3.5 μm)|LDC(40 nm)|LWO(1 μm)|LDC(40 nm)|LSCF, respectively. Cell performance tests were performed at 600 °C supplying 3% humidified H2 + Ar gas for the anode and 3% humidified 20% O2 + Ar gas for the cathode. The calculated OCV of the BZY monolayer model was 1.08 V and steeply increased up to 1.13 V by employing the thin LWO layer with L LWO/L total of 0.017 owing to suppression of the leakage current. Calculated dependences of ε and the power density for the model are shown in Fig.1. The efficiency and the power density showed a steep increase with increasing L LWO/L total. They showed the maximum values at certain L LWO/L total values, and then gradually decreased as L LWO/L total approached 1. This calculation result indicates that the cells exhibiting both the high ε and the high power density can be developed by employing the bilayer structure with the thin LWO hole blocking layer. Moreover, It is notable that, as the performance of the bilayer cell can be tuned by changing as presented in Fig. 1, the bilayer structure increases a degree of freedom for the design of the cells to satisfy various performance requirements. In the experiments, an enhancement of the OCV from 0.95 V for the BZY monolayer cell to 1.01 V for the bilayer cell was actually observed as suggested by the calculation. We consider that these theoretical calculations and experimental results present the effectiveness of the LWO hole blocking layer for the development of the high-performance PCFCs with high-design flexibility. Figure 1

Domain structures in polar materials provide an additional degree of freedom to tune ferroelectric photovoltaic (PV) effects. One of the approaches to control domain structures is to form a solid solution with analogs in different symmetries. In this study, we investigate the influence of domain structures on the PV properties of ferroelectric thin films in the xBaTiO3–(1−x)BiFeO3 (BT–BFO) solid-solution system (x = 0.1 and 0.2). We found that a substitution of BT for BFO substantially decreases the domain size down to several tens of nanometers, leading to an enhanced PV response owing to a marked contribution of the domain-wall PV effect.