Papers by Keyword: Barium Zirconate

Abstract: Protonic conductors of BaZr_0.5Ce_0.3Ln_0.2O_3-δ (BZCLn532, Ln=Y, Sm, Gd, Dy) were successfully synthesized by using a cost-effective solid state reactive sintering (SSRS) method with 1 wt.% NiO was added as a sintering aid. The pellets of the BZCLn532 were obtained at sintering temperatures between 1300 - 1600 °C. The results show that the morphologies and the final relative densities of the obtained BZCLn532 pellets are influenced significantly when different sintering temperatures were applied. Densified pellets of the BZCLn532 can be prepared at sintering temperatures of 1600 °C (BaZr_0.5Ce_0.3Y_0.2O_3-δ) and 1400 °C (BaZr_0.5Ce_0.3Sm_0.2O_3-δ, BaZr_0.5Ce_0.3Gd_0.2O_3-δ and BaZr_0.5Ce_0.3Dy_0.2O_3-δ,). The conductivity results show that the BaZr_0.5Ce_0.3Y_0.2O_3-δ (BZCY532) and BaZr_0.5Ce_0.3Dy_0.2O_3-δ (BZCD532) ceramics are demonstrated to be good candidates of oxygen ion conductor and proton conductor materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) applications.

Abstract: Investigation on polycrystalline electroceramics involves the synthesis, the consolidation and the analysis of the electrical behavior, along with careful evaluation of the final microstructure. The synthesis of ceramic powders with controlled characteristics is crucial in the study of materials with optimized properties. Distinct properties may be found in ceramic materials prepared by the several existing methods, due to chemical and phase homogeneities, and to the particle size distribution or medium particle size. In this work, yttrium-doped barium zirconate proton conductor was synthesized by spray pyrolysis, and characterized by several techniques aiming identifying the influence of some parameters of this method of synthesis with particle characteristics. Nanocrystalline powders synthesized at 600-700oC were found to be cubic and single phase. Moreover, depending on the gas flow and furnace temperature, spheroid and porous or cubic and solid particles may be obtained.

Abstract: The perovskite-type Ba(Zr_0.63Ce_0.27)Y_0.1O_3-δ (BZCY) was synthesized by solid-state reaction. Sintering behavior and electrical conductivity of the electrolyte materials were improved through optimizing the content of ZnO as sintering aid. The obvious enhancement of density of sintered body was observed due to ZnO reacting with BZCY powder. Relative densities of the samples increased with ZnO content added. A conductivity of 9.27×10^-3 S/cm tested in humid hydrogen at 800°C was obtained when the ZnO content was 2 mol%. A peak power density of 12.4 mW/cm² was delivered based on a single fuel cell with electrolyte-supported configuration.

Abstract: We study the formation mechanism of nanoparticles in thin films of the superconductor YBa₂Cu₃O_7-δ (YBCO). We form the films by metal-organic deposition (MOD) on buffered, textured metal substrates. Through the addition of Dy or Zr salts to the precursor solution we precipitate (Y,Dy)₂O₃ and BaZrO₃ nanoparticles, uniformly distributed through the film thickness. By quenching samples during the film growth, we show the nanoparticles form in the precursor layer before YBCO growth. The size of the nanoparticles was quantitatively analysed by TEM. We found that Zr doping produces smaller nanoparticles than Dy doping.

Abstract: Barium zirconate fine powders of pure cubic phase were readily prepared from the reactions between BaCl22H2O and ZrOCl28H2O under ammonothermal conditions at a very low temperature of 130oC as the lowest. KOH concentration was important in determining phase formation and particle morphology. Reaction temperature and time showed influences on the evolution of particle morphology and aggregation formation, respectively. Sizes of the primary particles critically depended on the BaII:ZrIV mole ratio. Phase formation mechanism is suggested.

Abstract: An all-oxide composite consisting of alumina fiber, alumina matrix, and barium zirconate interphase has been investigated. The barium zirconate interphase was applied on alumina fibers through coating via a sol-gel route. The incorporation of the coatings did not significantly influence the densification behavior of the composite under hot-pressing conditions. During the processing of the composite, the barium zirconate reacted in situ with alumina fiber and alumina matrix to form Ba-β-alumina platelets with an elongated morphology, which is propitious for crack deflection and thus toughness enhancement. The results reveal that it is possible to reduce fiber strength degradation by controlling the coating and densification processes.