Tianmin He

Synthesis and characterization of IT-electrolyte with perovskite structure La0.8Sr0.2Ga0.85Mg0.15O3−δ by glycine–nitrate combustion method

The intermediate-temperature electrolyte with perovskite-type La0.8Sr0.2Ga0.85Mg0.15O3-delta (LSGM) was synthesized using glycinenitrate combustion method. The formation process of the LSGM phase was investigated using DTA-TGA and XRD, and the thermal and electrical properties of the sintered samples were studied by thermal expansion and ac impedance technology. The research results show that the formation process of the LSGM phase suffered several different reaction stages. The perovskite phase was formed essentially at a sintering temperature of 1200 degreesC. The stable perovskite phase was formed completely after a sintering temperature of 1400 degreesC. The sinterability shows that the sintering temperature of the sample, which was synthesized by glycine-nitrate combustion method, is at least 100 degreesC lower than that of the conventional solid state method that was reported previously. The thermal expansion coefficient of the LSGM is somewhat higher than that of the YSZ. Impedance spectra indicate that the grain boundary resistance of the LSGM synthesized by glycine-nitrate combustion method is smaller. The conductivity of sample sintered at 1500 degreesC is higher than that at 1550 degreesC. The conductivity of a sample is 7.8X10(-2) S cm(-1) at 850 degreesC. The thermal analysis shows that the LSGM is relatively stable over an intermediate temperature range of 500-800 degreesC

Single intermedium-temperature SOFC prepared by glycine-nitrate process

A combustion synthesis method, the glycine-nitrate process, was used to prepare all nano-size materials used in a single intermedium-temperature solid-oxide fuel cell (IT-SOFC). Samaria-doped ceria (CeO2)(0.9)(SmO1.5)(0.1) (SDC) was used as electrolyte, La0.6Sr0.4Fe0.8Co0.2O3 (LSCF) with 50 wt% SDC was selected as the cathode, and a SDC-Ni composite powder was used as the anode. In this study, the performance of the SOFC was obtained from 250 to 750 degreesC. The highest open circuit voltage was about 0.95 V at 450 degreesC and the maximum power density of 0.104 W cm(-2) and a short circuit current density of 500 mA cm(-2) of the cell were achieved at 750 degreesC. The initial cell performance showed that, with a proper choice of synthesis process and technology, a SOFC using CeO2-based materials as electrolyte operating at IT-temperature is a realistic goal

Study on the properties of Al2O3-doped (ZrO2)0.92(Y2O3)0.08 electrolyte

Abstract Alumina (Al 2 O 3 ) is doped into cubic structured yttrium stabilized zirconia (ZrO 2 ) 0.92 (Y 2 O 3 ) 0.08 (YSZ) by a ceramic method. The influence caused by the access of Al 2 O 3 on the sintering behavior, mechanical and electrical properties of YSZ are studied, and the mechanism is analyzed. The experiments show that doping Al 2 O 3 to YSZ can significantly improve the sintering behavior by reducing sintering temperature. Impedance analysis shows that the electrical properties can be also improved by doping Al 2 O 3 because of the improvement of grain boundary conditions. YSZ doped with different amount of Al 2 O 3 have different grain boundary conductivities among which the highest value belongs to the specimen of YSZ doped with 4 wt% Al 2 O 3 . Pure YSZ and YSZ doped with 4 wt% Al 2 O 3 are used as the electrolytes to make SOFCs. The performance of SOFC with an Al 2 O 3 doped electrolyte is better than that with a pure YSZ one.

Properties of nonstoichiometric Pr0.6−xSr0.4MnO3 as the cathodes of SOFCs

A series of samples Pr0.6-xSr0.4MnO3 (x = 0, 0.01, 0.05, 0.1, 0.15, 0.2) were synthesized by a solid state reaction method. Pr deficiency at the A site has a great effect on the properties of Pr0.6-xSr0.4MnO3 as the cathode of SOFCs (solid oxide fuel cells). Compared to the commonly used La0.6Sr0.4MnO3 and La0.55Sr0.4MnO3 cathode, Pr0.6-xSr0.4MnO3 is better in the properties of conductivity, overpotential and impedance. In all the samples, the one with x = 0.05, Pr0.55Sr0.4MnO3, revealed the best performance in the measured temperature range

Characterization of YSZ electrolyte membrane tubes prepared by a vacuum casting method

Abstract Eight mol% YSZ electrolyte membrane tubes with a thickness of 0.2 mm were made using a vacuum casting method. The sintered densities, microstructure and electrical conductivity of the YSZ electrolyte membrane tubes were studied using the Archimedes water immersion technique, SEM and complex impedance, respectively. The sintering temperature corresponding to optimal sinterability for the YSZ electrolyte membrane tubes was determined. The research results show that vacuum casting is a simple way of preparing YSZ electrolyte membrane tubes with high density and high electrical conductivity. YSZ electrolyte membrane tubes with a relative density of 98.1% and 254 mm in length are fabricated using this method. The range of sintering temperatures is 190–200°C lower than that of the conventional slip casting. The densification and the electrical conductivity of the samples increase gradually with the increase of the sintering temperature. The density and electrical conductivity of the samples reach an optimum value at a sintered temperature of 1600°C for 2 h. As the sintering temperatures are raised further, both the density and the electrical conductivity of the samples decrease.

Study on new copper-containing SOFC anode materials

Abstract A series of new Ni–Cu–YSZ cermet made of oxide raw materials was employed as the anode of a SOFC. The reducing properties of these materials were first investigated. The open circuit voltage was over 1.1 V, and the output power density was about 33–43 mW/cm2 at 900°C. Altering the fuel gas between H2 and city coal gas shows that the output voltage and power are affected by fuel, and the response of fuel cell to the fuel gas is rapid. When pitch exists in the fuel gas, a tar-liked carbon is deposited on the Al2O3 tubes of the cell but not on the anode. It has been proved that the anode with Cu has a self-cleaning function.

Electrical properties of thin-walled 8 mol% yttria-stabilized zirconia electrolyte tubes prepared by an improved slip casting method

Yttria (8 mol %)-stabilized zirconia electrolyte tubes with thin walls, which are 266 mm in length, 0,4-0.9 mm in thickness, and 96.7% in relative density, were prepared with an improved slip casting method. The microstructure and electrical properties of the samples sintered at different temperatures were studied using SEM and a.c. impedance spectroscopy. The effects of sintered density, grain and grain boundary on the electrical properties of samples were analyzed. The results show that the densification of samples increases gradually with increasing sintering temperatures. The microstructure of samples strongly influences their electrical properties, and with increasing sintered density, the electrical properties of samples are enhanced. The ionic conductivity of grain and grain boundary is improved as the sintering temperatures increase. The grain boundary resistance of samples sintered at 1650degreesC is higher than that of samples sintered at 1600degreesC. Better sinterability of samples was obtained at a sintering temperature of 1650degreesC

The Pr4+ ions in Mg doped PrGaO3 perovskites

In this study, the valence state of Pr in Mg doped PrGaO3 perovskites was investigated. It is found that Pr4+ ions are created in samples doped with low-valence ions, for example, with Mg2+. The color of the doped samples changes from black to light green after being treated in H-2 atmosphere, which shows that the Pr4+ ions in the sample are reduced to Pr3+ ions. The open circuit voltage of the solid oxide fuel cell (SOFC) using PrGa0.95Mg0.05O3 as the electrolyte increases with time and the X-ray photoelectron spectroscopy (XPS) data of PrGa0.9Mg0.1O3 also show the existence of Pr4+ ions in Mg doped PrGaO3

Preparation and Electrochemical Performance of Cobalt-free Cathode Material Ba 0.5 Sr 0.5 Fe 0.9 Nb 0.1 O 3- δ for Intermediate-temperature Solid Oxide Fuel Cells

Perovskite oxide Ba0.5Sr0.5Fe0.9Nb0.1O3−δ(BSFN) as a cobalt-free cathode for intermediate-temperature solid oxide fuel cells(IT-SOFCs) on the Ce0.8Sm0.2O1.9(SDC) and La0.9Sr0.1Ga0.8Mg0.2O3−δ(LSGM) electrolytes was prepared and investigated. The single phase BSFN oxide with a cubic perovskite structure and relatively high electrical conductivities was obtained after sintering at 1250 °C for 10 h in air. The BSFN cathode exhibited excellent chemical stability on the SDC and LSGM electrolytes at temperatures below 950 °C. The area specific resistance of the BSFN cathode on the SDC and LSGM electrolytes were 0.024 and 0.021 Ω·cm2 at 800 °C, respectively. The maximum power densities of the single cell with BSFN cathode in 300 μm-thick SDC and LSGM electrolytes achieved 414 and 516 mW/cm2 at 800 °C, respectively. These results show that the BSFN material is a promising cobalt-free cathode candidate to be used in IT-SOFCs. A combination of the BSFN cathode and LSGM electrolyte is preferred owing to its excellent electrochemical performance.