Mg-Fe-Al-O系スピネル固溶体単結晶中の酸素拡散に対する酸化-還元過程の影響 Effects of redox processes on oxide ion diffusion in Mg-Al-Fe-O solid solution single crystals
Oxide ion diffusivities were evaluated in single crystals of Mg-Al-Fe-O spinel solid solutions. The single crystals were grown by a traveling solvent floating zone technique. The diffusion coefficients of oxide ions were obtained by means of a solid-gas exchange method, using <SUP>18</SUP>O isotope as tracer. The secondary mass spectrometer was used to measured the oxygen diffusion profiles in solids. Some profiles was not able to be interpreted by a simple error function. These anomalies are considered to be due to oxidizing or reducing process in the single crystals during the oxygen diffusion annealing. Iron ions preferentially diffused to surface during oxygen diffusion annealing in Mg<SUB>0.93</SUB>Al<SUB>1.24</SUB>Fe<SUB>0.83</SUB>O<SUB>4+δ</SUB>-crystals, while Mg<SUB>0.91</SUB>Al<SUB>0.72</SUB>Fe<SUB>1.37</SUB>O<SUB>4+δ</SUB>-crystals have not these behaviors. The resultant diffusion coefficient of Mg<SUB>0.91</SUB>Al<SUB>0.72</SUB>Fe<SUB>1.37</SUB>O<SUB>4+δ</SUB>-crystals were divided two temperature dependence as follows;<BR>D=2.0×10<SUP>-1</SUP>exp(-372(kJ/mol)/RT)cm<SUP>2</SUP>⋅s<SUP>-1</SUP>>1530K<BR>D=1.0×10<SUP>-7</SUP>exp(-181(kJ/mol)/RT)cm<SUP>2</SUP>⋅s<SUP>-1</SUP><1530K<BR>This tendency agreed with the polycrystalline data. In these samples it is considered that the oxide ions diffuses through oxygen vacancies.
粉体および粉末冶金 46(1), 36-47, 1999-01-15
Japan Society of Powder and Powder Metallurgy