Papers by Keyword: Solid Electrolyte

Abstract: Through computer aided design, manufacturing and evaluation, various ceramics dendrites with spatially ordered micro cavities were successfully fabricated by utilizing stereolithography. Micrometer order ceramic lattices were propagated spatially in computer graphic space. Ceramics nanoparticles were dispersed in to photo sensitive liquid resins to obtain thixotropic slurries. The paste material was spread on a grass substrate by using a mechanical knife edge, and an ultra violet micro pattern was exposed to create cross sectional solid layer. After the layer stacking process, the obtained composite precursor was dewaxed and sintered in an air atmosphere. By the micro patterning stereolithography, solid electrolyte dendrites of yttria stabilized zirconia with spatially ordered porous structures were fabricated for fuel cell miniaturizations. Gaseous fluid profiles and pressure distributions in the formed ceramic lattices with various porosity percent were visualized and analyzed by a finite element method. Subsequently, alumina micro photonic crystals with a diamond lattice structure were fabricated. Electromagnetic wave properties were measured by using a terahertz time domain spectroscopy. A complete photonic band gap was exhibited, and a localized mode to select the wavelength was obtained by introducing a defect cavity.

Abstract: In this study, powders of BaCe_0.54Zr_0.36Y_0.1O_2.95 (BCZY) were synthesized by a sol-gel method assisted with three different groups of chelating agents. The chelating agents used were citric acid, tartaric acid, glycolic acid from carboxylic group, tryelthylenetetraamine (TETA) from polyamino group, nitriloaacetic acid (NTA) and ethylenediaaminetetraacetic acid (EDTA) from polyamino carboxylic group. The samples were dried at 325 °C and calcined at a series of temperatures. The solution and resulting powder properties were studied using Fourier transform Infrared (FTIR) spectroscopy. FTIR spectra showed all the samples exhibit different characteristics of absorption bands after being treated at various temperatures. Such behavior indicates that the chelation process took place before the formation of metal oxide. The chelating agent from polyamino group that consists of N-donor atoms, which is TETA showed no characteristics peak of carbonates was detected after the sample was calcined at 1100 °C. Therefore, TETA gave a significant role in reducing calcination temperature for synthesizing cerate-zirconate powder.

Abstract: This paper discusses the crystal structure, the conductivity character and ionic migration inside Sm_0.2Ce_0.8O_1.9 (SDC) crystal and it’s composite with sodium carbonate salt, Na₂CO₃ (NSDC). XRD measurement equipped with Le Bail refinement shows that SDC crystallized in single phase of cubic with space group of Fm3m. The addition of Na₂CO₃ does not change the crystal structure of SDC however it increases the cell parameters. NSDC has a lower ionic conductivity than the SDC at the same temperature. However at 600 °C, SDC provides electronic conductivity which indicates the diffusion of electrons between the electrolyte and electrode caused by the reduction of Ce(IV) to Ce(III). It may cause a short circuit and the fuel cell performance if it is used as electrolyte. Meanwhile, NSDC still produces pure ionic conductivity at 600 °C which indicates a better chemical stability. Based on its capacitance values, it is known that the ionic conductivity of SDC is generated by migration of ions inside grain, while the conductivity of NSDC is generated by the migration of ions between grains or it is named as grain boundaries conductivity.

Abstract: The preparation of the BaZr_0.8Y_0.2O_3-δ solid electrolyte obtained by a nitrate-citrate combustion is reported. This synthesis method is compared with solid state reaction. The phase formation process was studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The phase evolution during the gel-combustion process and solid state process as a function of heat-treatment temperature was also studied by X-ray powder diffraction (XRD). When using nitrate-citrate combustion method a pure phase was formed at 800°C, which is much lower than that of conventional solid state reaction (at 1200°C). The sinterability of electrolyte powder was also investigated. At 1700°C very dense pellets can be obtained for both samples. The conductivity of BaZr_0.8Y_0.2O_3-δ (BZY20) electrolyte prepared using two different processes was measured by AC impedance spectroscopy. Impedance spectra analyses showed that the grain boundary conductivity is much lower than that of the bulk for BZY20. Furthermore, the grain-boundary resistance of the BZY20 prepared via nitrate-citrate combustion process was reduced markedly compared to that of the BZY20 prepared by conventional solid state reaction.

Abstract: Composites of mesoporous SiO₂ and LiAlCl₄ were synthesized, and the change in ionic conductivity due to the formation of the composites was investigated. The electrical conductivity of the composite with the SiO₂ : LiAlCl₄ of 2 : 3 was the highest with a value of 2 x 10^-6 S/cm at room temperature. A higher order of conductivity was observed for the composite compared to the non-composite LiAlCl₄. In addition, it was found that the conductivity of the composites depends on the pore size of the mesoporous SiO₂.

Abstract: LaYO₃ doped-ZrO₂ ceramic with the composition La_0.95Zr_0.05YO_3+δ was prepared via the solid state reaction. The samples were sintered at 1450 °C and sintering times in range of 6-15 hours have been varied for both doped and base samples in order to study its effect on its properties. The results showed that relative density increased remarkably with sintering time. The highest relative density was observed for the samples sintered for 15 hours. Scanning electron micrographs also proved that the porosity of the samples reduced when samples sintered for the longer time.

Abstract: La_0.95Sr_0.05GaO2.975 has been prepared by conventional solid state reaction method. The calcined sample has been isostatically pressed into pellets at a load of 12 kN cm^-2 and then sintered at 1400 °C for 12h. The crystalline phase formation and composition has been examined by X-ray diffraction (XRD) method. Dielectric relaxation of the samples has been investigated in the steps of 25 °C in the temperature range 200-600 °C and frequency range of 1-10⁶ Hz. The bulk and grain boundary contribution with frequency has been studied using Nyquist plots. The equivalent circuit model have been drawn which are well fitted with the plots. The activation energy has been found in the range of Ea = 0.95 eV which indicates that the prepared sample is essentially ionic conductor.

Abstract: Li₂O-Al₂O₃(La₂O₃)-TiO₂-P₂O₅ glass-ceramics were fabricated through heat-treatment of the original glass. The differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical workstation were employed to study the structural, morphology and electrical properties of the samples heat-treated at different temperatures. The results showed that: the glass-ceramics consist of the dominating LiTi₂(PO₄)₃ phases, trifle AlPO₄, TiO₂ and unknown phases. With the heat-treatment temperature increasing from 700 °C to 1100 °C, the structure of glass-ceramic become denser and grain grew, lithium ion conductivity increased quickly and subsequent cut down gradually. While the specimen was obtained by crystallization at 900 °C for 12 h, the total conductivity of glass-ceramic material come up to the maximum (5.85 ×10^-4 S•cm^-1) at 25 °C. This inorganic solid electrolyte has a potential application in lithium batteries or other devices.

Abstract: The (ZrO₂-1.6P₂O₅)-PTFE composite electrolytes have been prepared by mixing PTFE powders with different particle sizes and the shell-core-type ZrO₂-1.6P₂O₅ electrolyte, synthesized by solid state reaction with diammonium hydrogen phosphate, to improve the mechanical strength of the electrolyte. The H₂ gas permeability decreased and the cell performances improved with decreasing PTFE-particle size. The aging at 0.4 V above 443 K enhanced the ITFC performance owing to the penetration of the electrolyte to the carbon paper. The maximum output power enhanced by 63% after 15 h of aging at 573 K.

Abstract: This paper presents a micro solid electrolyte CO2 gas sensor in which Li2CO3, Li2TiO3-TiO2 serves as sensing and reference electrodes respectively, and the Li3PO4 film acts as the electrolyte. The sensor was constructed in the sequent layers of O2, CO2, Li2CO3, Pt | Li3PO4 | Pt, Li2TiO3-TiO2, O2, CO2 on the Al2O3 substrate by MEMS process. Experimental results indicate that the micro solid-electrolyte CO2 gas sensor has a relatively rapid speed of response. By discussions, we may find that the improved performance will be realized by optimizing the primary parameters of the sensor.