La Ga Research Articles

Heterogeneous Composite Fibrous Cathode Undergoing Emphasized Active Oxygen Dissociation for La(Sr)Ga(Mg)O3‐Based High‐Performed Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are of great importance in terms of reducing operational costs and benefiting from system durability. However, SOFCs exhibit sluggish oxygen reduction reactions (ORRs) at cathodes. To overcome this, extensive research is focused on the development of cathodes with superior ORR properties for SOFCs. In this study, a fibrous composite cathode composed of strontium‐doped samarium cobaltate (SSC) and samarium‐doped ceria (SDC) is fabricated via electrospinning. Composite fiber cathodes prepared at specific ratios exhibit ORR properties and oxygen‐ion conductivity, which are attributed to the growth of small SSC particles in the fibrous electrode and nanolattice strain of SSC at the SSC and SDC interface. As such, the enhanced cathode performance contributes to an improvement in the power‐generation characteristics of SOFCs (1.33 W cm−2 at 1073 K using 300 μm thick La(Sr)Ga(Mg)O3 electrolyte). This structural engineering of dual‐phase fiber is a promising design that promotes cathodic ORR performance.

Solubility of Lanthanum in Liquid Alloys with Gallium and Indium

The solubility of lanthanum in indium and Ga–In alloys containing 21.8, 40 and 70 wt. % In was determined experimentally at temperatures up to 1081 K. The low temperature limit depended on the melting point of the alloy. The solubility was measured using isothermal saturation and high-temperature filtration methods. The phase composition of solid intermetallic compounds formed in the ternary La–Ga–In systems of various compositions was determined by X-ray diffraction. Activity coefficients of lanthanum in the alloys based on gallium, indium and three Ga–In mixtures (21.8, 40 and 70 wt. % In) were calculated. Temperature dependencies of thermodynamically possible separation factors for the uranium/lanthanum couple in “LiCl–KCl–CsCl melt–liquid alloy” systems were derived for various gallium–indium alloys.

Towards deliberate design of persistent phosphors: a study of La–Ga admixing in LuAG:Ce crystals to engineer elemental homogeneity and carrier trap depths

Persistent luminescence in Lu3Al2Ga2O12:Ce,La crystal was studied. La codoping elongated luminescence and increased trapping centers. The influence of La on crystal growth, structure, and Al/Ga sublattices was analyzed.

Phase formation between La(Sr)Ga(Mg)O3 and Ce(La)O2 for solid oxide fuel cell applications

AbstractIn strontium‐ and magnesium‐doped LaGaO3 (LSGM) electrolyte‐based solid oxide fuel cells (SOFC), lanthanum‐doped CeO2 (LDC) is usually used as buffer layer material to prevent reactions between LSGM electrolyte and NiO‐based anode. In literature, based on results for one particular LSGM composition, a fixed buffer layer composition of 40% La‐doped ceria (LDC40) has been used even with electrolytes of different LSGM compositions. In this study, we report the results of a comprehensive study of phase formations between various LSGM and LDC compositions. Our results show that only one LSGM/LDC combination results in no additional phases. For the other combinations, at least one and often two additional phases, LaSrGaO4 and LaSrGa3O7, result. Because LaSrGa3O7 has much lower conductivity, it is necessary to select combinations that avoid this phase. We propose that the combination that results in no additional phase should be considered favorably for SOFCs. For other LSGM compositions, LDC50 should be used as a buffer layer instead of LDC40 as is presently done in SOFC studies. Alternately, if LDC40 is preferred for buffer layer, then lower Sr content LSGM compositions should be used as electrolytes. These combinations are likely to lead to better long‐term SOFC performance.

Recent Advances in High Temperature Electrolysis Cells using LaGaO3-based Electrolyte

High temperature electrolysis is a promising option for carbon-free hydrogen production and huge energy storage with high energy conversion efficiencies from renewable and nuclear resources. Over the past few decades, yttria-stabilized zirconia (YSZ) based ion conductor has been widely used as a solid electrolyte in solid oxide electrolysis cells (SOECs). However, its high operation temperature and lower conductivity in the appropriate temperature range for solid electrochemical devices were major drawbacks. Regarding improving ionic-conducting electrolytes, several groups have contributed significantly to developing and applying LaGaO3 based perovskite as a superior ionic conductor. La(Sr)Ga(Mg)O3 (LSGM) electrolyte was successfully validated for intermediate-temperature solid oxide fuel cells (SOFCs) but was rarely conducted on SOECs for its high efficient electrolysis performance. Their lower mechanical strengths or higher reactivity with electrode compared with the YSZ electrolysis cells, which make it difficult to choose compatible materials, remain major challenges. In this field, SOECs have attracted a great attention in the last few years, as they offer significant power and higher efficiencies compared to conventional YSZ based electrolysers. Herein, SOECs using LSGM based electrolyte, their applications, high performance, and their issues will be reviewed.

Recent Advances in High Temperature Electrolysis Cells using LaGaO3-based Electrolyte

High temperature electrolysis is a promising option for carbon-free hydrogen production and huge energy storage with high energy conversion efficiencies from renewable and nuclear resources. Over the past few decades, yttria-stabilized zirconia (YSZ) based ion conductor has been widely used as a solid electrolyte in solid oxide electrolysis cells (SOECs). However, its high operation temperature and lower conductivity in the appropriate temperature range for solid electrochemical devices were major drawbacks. Regarding improving ionic-conducting electrolytes, several groups have contributed significantly to developing and applying LaGaO3 based perovskite as a superior ionic conductor. La(Sr)Ga(Mg)O3 (LSGM) electrolyte was successfully validated for intermediate-temperature solid oxide fuel cells (SOFCs) but was rarely conducted on SOECs for its high efficient electrolysis performance. Their lower mechanical strengths or higher reactivity with electrode compared with the YSZ electrolysis cells, which make it difficult to choose compatible materials, remain major challenges. In this field, SOECs have attracted a great attention in the last few years, as they offer significant power and higher efficiencies compared to conventional YSZ based electrolysers. Herein, SOECs using LSGM based electrolyte, their applications, high performance, and their issues will be reviewed.

(Invited) Effects of Cobalt Co-Doping on Mixed Ion Conductivity in La(Sr)Ga(Fe)O3 for Oxygen Separation

Mixed ion conductor shows oxide ion and electronic conduction simultaneously and expecting for application to oxygen separation membrane from air. Because of significant volume change depending on oxygen partial pressure, oxygen separation membrane using mixed ion conductor has disadvantage of narrow range of oxygen partial pressure resulting in the limited permeation rate. Therefore, increased oxide ion conductivity and mechanical strength have been required for mixed ion conducting membrane for oxygen separator. In our previous study, we found that Fe doped LaGaO3 shows reasonably high oxide ion conductivity and chemical stability. In particular, La0.7Sr0.3Ga0.6Fe0.4O3 (LSGF) shows largest oxide permeation rate from air to He. In this study, for further increase in oxygen permeation rate, effects of dopant to Ga site in LSGF was investigated. Application to CH4 partial oxidation was also studied. All LSGF sample was prepared with conventional solid state reaction method using oxide as source materials. Partial substitution was performed for Ga site in LSGF and dense sample without impurity phase was confirmed by XRD measurement. For oxygen permeation measurement, La0.6Sr0.4CoO3 catalyst was coated on the surface of LSGF disk (Φ17mm diameter, 0.5mm thickness) It was found that the oxygen permeation from air to He was sensitively influenced by dopant and the oxygen permeation rate was increased as the following order, Co>Al>In>Ni>Mn at 1273 K. On the other hand, in case of Ru and Ir which is easily reduced to metallic state decreased the oxygen permeation rate significantly. Therefore, it was found that addition of 10 mol % of Co or Al is effective for increasing oxygen permeation rate of LSGF. Effects of Co in LSGF was further studied from oxygen permeation rate and the highest oxygen permeation rate was achieved at 3 mol% in Ga site of LSGC. On this optimized composition, La0.7Sr0.3Ga0.57Fe0.4Co0.03O3, shows 225 μmol min-1 cm-2 at 1273 K and this value is almost 2.5 times larger than that of LSGF. Effects of small amount of Co on electrical conductivity in LSGF were also studied. Although LSGF shows high hole conduction like log(σ/Scm-1)=0.6, the conductivity was increased by Co doping, in particular, at lower temperature. In contrast, Al doping decreases total conductivity and so, increase in oxygen permeation rate could be assigned to the increased mobility of oxide ion in LSGF. Application of Co doped LSGF to CH4 partial oxidation was further studied. Although optimized amount of Co doped for Ga site in LSGF is 3 mol%, the membrane was broken when 3 mol% doped LSGF was used for oxygen membrane. 1% Co doped LSGF was applied for oxygen permeation membrane and it was found that amount of oxygen permeation rate was 1.5 times increased comparing with LSGF. In addition, no crack was formed in membrane. The amount of oxygen permeation was achieved 364μmol cm2 min-1 which is corresponded to 8.9ml/min cm2 at 1273K. In summary, this study reveals that doping small amount of Co to Ga site of LSGF is highly effective for increasing oxygen permeation rate without decreasing chemical stability.

An innovative occluder for cardiac defect: 3D printing and a biocompatibility research based on self-developed bioabsorbable material-LA-GA-TMC.

This study adopted the latest self-developed bioabsorbable material lactide-glycolide-1,3-trimethylene carbonate (LA-GA-TMC) and applied the three-dimensional (3D) printing technique to manufacture the occluder for cardiac septal defects, so as to realize the individualized treatment of cardiac septal defects. At the same time, its biosafety was evaluated, with an aim to establish foundation for futural large-scale animal experiment and clinical trial. The traditional "one-pot synthesis" was modified, and the "two-step synthesis method" was utilized to synthesize the LA-GA-TMC terpolymer at the lactide: glycolide: trimethylene carbonate ratio of 6:1:1.7. Afterward, the synthesized terpolymer was used as the raw material to fabricate the occluder model via using 3D printing technique. Then, its biocompatibility was comprehensively evaluated through cytocompatibility, blood compatibility, and histocompatibility. The occluder made from LA-GA-TMC 3D printing had favorable ductility and recoverability; besides, it possessed the temperature-control feature, and the relative cell proliferation rates in extract liquids at various concentrations were all >70%, suggesting that it had favorable cytocompatibility. Moreover, hemolytic experiment revealed that its hemolytic rate was <5%, dynamic blood coagulation experiment demonstrated that the sample material moderately activated the blood coagulation, and the above findings suggested that it had good blood compatibility. In addition, implanting experiment in vivo revealed that its histocompatibility was superior to the traditional nitinol and the emerging poly-l-lactic acid. It is completely feasible to manufacture the cardiac septal defects occluder based on the novel absorbable material LA-GA-TMC, which has favorable biocompatibility, through 3D printing technique and it possesses broad prospects in large-scale animal experiment and clinical trial.

Activity coefficients of lanthanum in gallium and gallium-aluminum based alloys

Activity of β-lanthanum were determined in gallium and gallium-aluminum alloy (12 mol. % Al) at 573–1081 K and 573–999 K, respectively, using the electromotive force measurements method. Partial molar thermodynamic functions of lanthanum in the said alloys were calculated. Solubility of lanthanum in liquid gallium was measured between 368 and 1073 K and activity coefficients of β-lanthanum in liquid Ga and Ga–Al alloy calculated. Comparison of results obtained for La–Ga and La–Ga–Al alloys showed that addition of aluminum to Ga–La alloys had an insignificant influence on thermodynamic properties of lanthanum.

Fabrication of multilayer ceramic structure for fuel cell based on La(Sr)Ga(Mg)O3–La(Sr)Fe(Ga)O3 cathode

Fabrication by co-sintering method of a multilayer pore-free electrode–electrolyte structure promising for use in solid-oxide fuel cell and its characteristics have been studied. A material with high ionic conductivity of La0.88Sr0.12Ga0.82Mg0.18O3–δ (LSGM) served as electrolyte. The composite electrode was formed from a 1: 2 mixture of LSGM and LSFG (La0.7Sr0.3Fe0.95Ga0.05O3–δ). The maximum temperature of the materials co-sintering ability is 1250°C. It was shown by the impedance spectroscopy that the polarization resistance of the LSGM–LSFG electrode is 0.14 Ω cm2 at 800°C.

LaGa-based bulk metallic glasses**Project supported by the National Natural Science Foundation of China (Grant Nos. 51571209 and 51461165101), the National Basic Research Program of China (Grant No. 2015CB856800), and the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (Grant No. QYZDY-SSW-JSC017).

We report the formation of LaGa-based bulk metallic glasses. Ternary La–Ga–Cu glassy rods of 2–3 mm in diameter can be easily formed in a wide composition range by the conventional copper mold casting method. With minor addition of extra elements such as Co, Ni, Fe, Nb, Y, and Zr, the critical diameter of the full glassy rods of the La–Ga–Cu matrix can be markedly enhanced to at least 5 mm. The characteristics and properties of these new LaGa-based bulk metallic glasses with excellent glass formation ability and low glass transition temperature are model systems for fundamental issues investigation and could have some potential applications in micromachining field.

Influence of the nanoparticle sizes on the photo-induced absorption of La–Ga–S–O–Dy glass nanocomposites

We have established that the illumination by two coherent beams originating from nanosecond Nd:YAG laser at wavelengths 1064nm and 532nm in the La–Ga–S–O–Gd:PVA La-Ga-S-O-Dy polymer glass nanocomposites leads to substantial changes in the absorption. The effect is completely reversible and disappears after interruption of the optical treatment. The illumination power density was varied up to 0.6GW/cm2. All the samples show destruction less than 0.2% changes after more than 300,000 laser pulses. The beams were incident with the angles varying between 45° and 50° with respect to the nanocomposite surface. Moreover, the additional analysis of TEM did not demonstrate any additional aggregations. The role of light polarizations, beam stability, and light scattering is discussed.

Laser induced birefringence in La–Ga–S–O–Gd glass polymer nanocomposites

In this work, we demonstrate a possibility to use La–Ga–S–O–Gd glass polymer nanocomposites as effective materials for photo-induced birefringence. Here we chose PVA as a photopolymer matrix. The photo-induced effects were studied using 8 ns Nd: YAG laser generating bicolor coherent light beams with wavelengths 1064, and 532 nm. The detection of the photo-induced birefringence was carried out using cw He–Ne laser at 1150 nm. The optimal concentration of the nanoglass favoring maximal changes of refractive indices is established. The photo-induced laser power density was changed up to 0.9 GW/cm2. The photo-induced beams were incident at angles varying within the 32° and 52° with respect to the nanocomposite planes. The polarizations of the beams did not play principal role. We discovered an appearance of maximal birefringence equal to about 0.078. The effect is strongly dependent on the nanoparticle sizes and is completely reversible after switching off the laser treatment within several milliseconds. Such features are useful for the recording of optical information and production of gratings with desirable periods.

Thermodynamic properties of La–Ga–Al and U–Ga–Al alloys and the separation factor of U/La couple in the molten salt–liquid metal system

The electrochemical behaviour of lanthanum and uranium was studied in fused 3LiCl–2KCl eutectic and Ga–Al eutectic liquid metal alloy between 723 and 823 K. Electrode potentials were recorded vs. Cl−/Cl2 reference electrode and the temperature dependencies of the apparent standard potentials of La-(Ga–Al) and U-(Ga–Al) alloys were determined. Lanthanum and uranium activity coefficients and U/La couple separation factor were calculated. Partial excess free Gibbs energy, partial enthalpy of mixing and partial excess entropy of La-(Ga–Al) and U-(Ga–Al) alloys were estimated.

Reversible Type Solid Oxide Fuel Cells Using Ni-Fe-CeO2 Based Cermet Fuel Electrode and Applied for Metal-Air Rechargeable Battery

Solid Oxide Fuel Cells (SOFC) is expecting as a highly efficient energy convertor. On the other hand, recently, there are strong interests on high temperature steam electrolysis because of efficient hydrogen production method. In addition, reversible operation of SOFCs is also interesting as an energy storage method. Therefore, recently, there is also high interest on reversible operation type SOFC so-called SORC. At present, for SORC, similar materials for conventional SOFC are widely used, i.e., Y2O3 stabilized ZrO2 and Ni based cermet for electrolyte and fuel electrode, respectively. However, because of high temperature operation, energy efficiency as well as stability is still not high as an energy storage process. In this study, we investigated intermediate temperature SORC using LaGaO3 electrolyte. For reversible type operation, aggregation of Ni is easily occurred but it was found that addition of small amount of Fe is effective for preventing aggregation of Ni. The optimized composition for fuel electrode is Ni-Fe(9:1) from stability. Effects of mixed conducting oxide added for Ni-Fe were studied. For SOFC operation, power density is larger as the following order, Ce(Mn,Fe)O2<NiFe=La(Sr)Ga(Mg)O 3<Ce0.8Sm0.2O2< La(Sr)Fe(Mn)O3. On the other hand, for SOFC operation, the electrolysis current density is increased as the following order, Ce(Mn,Fe)O2<NiFe<La(Sr)Ga(Mg)O3<< La(Sr)Fe(Mn)O3 <Ce0.8Sm0.2O2. Therefore, for reversible operation, NiFe-SDC shows the most active. Degradation of the cell using NiFe-SDC and Sm(Sr)CoO3 for fuel and air electrode, respectively, was studied at 1073 K, 100mA/cm2. The observed terminal potential was 1.13 and 1.025 V for SOEC and SOFC respectively at initial cycle and the observed potential slightly increased for SOFC and decreased for SOEC with cycle number, however, after 50 cycles, the observed terminal potential was 1.15 and 1.0 V for SOFC and SOFC, respectively. Therefore, the degradation is hardly observed for the reversible operation of the cell. Combination of SORC with metal oxidation could open a new application area for fuel cell. In this study, application of various metals like Fe, Sn, Al, and Mg to SORC were studied by using CaO Stabilized ZrO2 for electrolyte and it became clear that redox of metal proceeded in SORC electrochemically resulting in the all solid state metal-air rechargeable battery. The observed open circuit potential is well agreed with theoretical PO2 from Gibbs free energy of metal oxidation. By decreasing operating temperature, PO2 range of electrolyte domain can be expanded. Application of LSGM for electrolyte of this new concept of oxygen redox shuttle battery will also be discussed.

Reversible Type Solid Oxide Fuel Cells Using Ni-Fe-CeO2 Based Cermet Fuel Electrode and Applied for Metal-Air Rechargeable Battery

Effects of mixed conducting oxide added for Ni-Fe were studied as fuel electrode of Solid Oxide Reversible Cells (SORC). For SOFC operation, power density is larger as the following order, BaCe(Y)O3<<YSZ<Ce(Mn,Fe)O2<NiFe=La(Sr)Ga(Mg)O3<Ce0.8Sm0.2O2<La(Sr)Fe(Mn)O3. On the other hand, for electrolysis operation, the electrolysis current density is increased as the following order, BCY<Ce(Mn,Fe)O2 <YSZ=NiFe< La(Sr)Ga(Mg)O3<<La(Sr) Fe(Mn)O3<Ce0.8 Sm0.2O2. Therefore, for reversible operation, NiFe- Ce0.8Sm0.2O2 (SDC) seems to be the most active. Degradation of the cell using NiFe-SDC and Sm0.5Sr0.5CoO3 for fuel and air electrode, respectively, was studied at 1073 K, 100mA/cm2. The observed terminal potential was 1.13 and 1.025 V for SOEC and SOFC respectively at initial cycle and the observed potential slightly increased for SOFC and decreased for SOEC with cycle number, however, after 50 cycles, the observed terminal potential was 1.15 and 1.0 V for SOFC and SOFC, respectively. Therefore, the degradation is hardly observed for the reversible operation of the cell. Combination of SORC with metal oxidation could open a new application area for fuel cell. In this study, application of SORC for reversible metal-air battery

520 mJ langasite electro-optically Q-switched Cr, Tm, Ho:YAG laser

A flash lamp pumped 2.09 μm Cr, Tm, Ho:YAG laser utilizing a self-grown La(3)Ga(5)SiO(14) crystal as the electro-optic Q-switch generator is proposed and demonstrated for the first time. Operating at 3 Hz repetition rate, 520 mJ pulse energy with 35 ns pulse width is achieved by optimizing the Q-switch delay time and compensating for the thermal depolarization with a quarter-wave plate. The corresponding peak power is 14.86 MW, and the Q-switched-to-normal-mode energy extraction efficiency is 66.3%. To our knowledge, this Q-switched giant pulse is the best result reported to date in 2.09 μm laser resonator.

Sol–gel synthesis of La0.6Sr0.4CoO3−x and Sm0.5Sr0.5CoO3−x cathode nanopowders for solid oxide fuel cells

Nano-powders of La0.6Sr0.4CoO3−x (LSC) and Sm0.5Sr0.5CoO3−x (SSC) compositions, which are being investigated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) with La(Sr)Ga(Mg)O3−x (LSGM) as the electrolyte, were synthesized by low-temperature sol–gel method using metal nitrates and citric acid. Thermal decomposition of the citrate gels was followed by simultaneous DSC/TGA methods. Development of phases in the gels, on heat treatments at various temperatures, was monitored by X-ray diffraction. Sol–gel powders calcined at 550–1000°C consisted of a number of phases. Single perovskite phase La0.6Sr0.4CoO3−x or Sm0.5Sr0.5CoO3−x powders were obtained at 1200°C and 1300°C, respectively. Morphological analysis of the powders calcined at various temperatures was done by scanning electron microscopy. The average crystallite size of the powders was ∼15nm after 700°C calcinations and slowly increased to 70–100nm after heat treatments at 1300–1400°C.

The investigation of (Bi,La)(Ga,Fe)O3–PbTiO3 thin film prepared by PLD technique

Abstract In this report, (Bi,La)(Ga,Fe)O 3 –PbTiO 3 (BLGF–PT) thin film was prepared on platinum coated Si wafer by pulsed laser deposition (PLD) method. BLGF–PT ceramic with morphotropic phase boundary (MPB) composition was used as the PLD target. The spot of Bi 2 Fe 4 O 9 impurity phase in X-ray diffraction profile implies a composition deviation in the BLGF–PT thin film from that of target. However, the MPB feature of co-existence of rhombohedral and tetragonal phases remains remarkable in the film. The characterization results of the leakage current and ferroelectric hysteresis loop indicate a desirable insulation in this BLGF–PT thin film. Polarization response by positive-up-negative-down pulse measurement and retention property are further carried out at room temperature to check the intrinsic ferroelectric performance. Moreover, high Curie temperature of 465 °C has been discovered in this BLGF–PT thin film, which may promote the application scope of the thin film.

Self-propagating high-temperature synthesis of La(Sr)Ga(Mg,Fe)O 3− δ with planetary ball-mill treatment for solid oxide fuel cell electrolytes

This study investigated the combined effects of self-propagating high-temperature synthesis (SHS), planetary ball-mill (PBM) treatment, and sintering temperature on La 0.7Sr 0.3Ga 0.7Mg 0.1Fe 0.2O 3− δ (LSGMF73712) as an electrolyte material for solid oxide fuel cells (SOFC). The SHS products (SHS-LSGMF73712) were compared with that prepared via solid-state reaction (SSR) in terms of sinterability and power generation performance. The SHS products were treated with PBM for 10, 30, 50, and 70 h. The SHS products contained the by-product LaSrGaO 4; however, in the SHS products treated with PBM for longer than 50 h, the by-product disappeared after sintering at 1350 °C for 3 h in air. Among the samples, SHS products treated with PBM for 70 h displayed superior sintering (1350 °C), whereas the SSR product (SSR-LSGMF73712) was successfully sintered at 1450 °C for 3 h in air. Under the cell configuration of Ni–Fe/SHS-LSGMF73712-PBM70 h (0.3 mm thick)/Sm 0.5Sr 0.5CoO 3, the maximum power density was 0.673 W/cm 2 at 800 °C using humidified hydrogen gas (3 mol% H 2O) as a fuel and air as an oxidizing agent at a flow rate of 100 mL/min, which was almost equivalent to that using SSR-LSGMF73712 (0.629 W/cm 2 at 800 °C) under the same conditions.