酸化物固体電解質ナノ複合粒子の合成と焼結

抄録

The synthesis of CeO₂/ZrO₂ core/shell nanocrystals (NCs), which are CeO₂ NCs overcoated by a thin ZrO₂ layer, has been studied together with CeO₂, Sm₂O₃ and Gd₂O₃ doped CeO₂ and ZrO₂ NCs by a hot-surfactant colloidal method. Colloidal oleylamine solutions of the CeO₂, and doped CeO₂ NCs with an approximately 2.0 nm diameter and ZrO₂ NCs with a 2.5～3.5 nm diameter were respectively synthesized by the thermolysis of metallic acetylacetonates and the nonhydrolytic sol-gel reaction of Zr[OCH(CH₃)₂]₄ and ZrCl₄. The CeO₂/ZrO₂ core/shell NCs have been successfully synthesized by the addition of CeO₂ NCs as seed crystals to the ZrO₂ source solution and its reaction at 300□. The core/shell nanostructure, which consists of a 2.4 nm diameter CeO₂-core and 1.2 nm thick ZrO₂-shell, was determined by its XRD and HREM results.

The synthesis of Y₂O₃-stabilized zirconia was attempted by the following procedure: Zirconium isopropoxide, zirconium chloride and yttrium isopropoxide were dissolved in oleylamine at 60□ for a hour. The Y-concentration of the starting solution were varied as 10, 20, 30 at% and then the solutions were heated at 340□ for 2 h under Ar atmosphere. The products were transparent and colloidal solutions. Average particle sizes of the product powders extracted from the solutions were ranged in 2.0～2.6nm diameter. The lattice parameter, calculated from XRD patterns, increased with the analytical concentration of Y in the obtained powders. Based on these results, it was concluded that the YSZ nanocrystals were successfully synthesized. The grain growth behavior of the obtained YSZ nanocrystals was also investigated. Distinct grain growth was not observed below 800□; steep grain growth occurred above 850□. The low temperature sintering at 600□ of the YSZ nanocrystals using SPS technique was attempted, however, the resulting compact showed 69% of the theoretical density. Further study was needed in order to obtain the high density sample with several nm in grain size.