固体の表面構造と相転移の研究 [in Japanese] Studies on the Surface Structure and Phase Transformation of Solids [in Japanese]
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The author shows two examples of phase transformation in some oxide ceramics, which is caused by the reaction of oxide ceramics and a vapor phase. The first example is a tetragonal-to-monoclinic transformation in ZrO<SUB>2</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> ceramics which takes place isothermally during low temperature aging in air, accompanying an weight increase. An absorption band at 3340 cm<SUP>-1</SUP> appears in FT-IR DRIFT spectrum in association with the appearance of monoclinic phase in ZrO<SUB>2</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> ceramics. The reaction between ZrO<SUB>2</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> ceramics and H<SUB>2</SUB>O in air, and the diffusion of OH- ions in the powders must be essential for this phase transformation to take place. The second case is an oxidation and reduction of powdered ceramic superconductor YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>y</SUB> In the case of isothermal reduction using orthorhombic powders, the reduction is controlled by the removing rate of oxygen from the particle surface. On the other hand, in a case of isothermal oxidation of tetragonal powders, the orthorhombic phase exists as a skin surrounding the unreacted core of the tetragonal phase. The oxidation is recognized to be controlled by the moving rate of the interface between the tetragonal and orthorhombic phases.
- J. Jpn. Soc. Powder Powder Metallurgy
J. Jpn. Soc. Powder Powder Metallurgy 44(10), 905-911, 1997-10-15
Japan Society of Powder and Powder Metallurgy