DIFFUSION COEFFICIENT IN CaAl_(12)O_(19) BY SOLID-STATE REACTION AND IONIC CONDUCTIVITY MEASUREMENT

摘要

The growth of CaAl_(12)O_(19) in diffusion couples of single crystal Al_2O_3 and poly-crystalline CaAl_4O_7 was investigated between 1573 and 1823 K. The growth rate of CaAl_(12)O_(19) obeyed a parabolic rate law. CaAl_(12)O_(19) was reported to have a layered structure composed of alternating layers of spinel block and ionically conductive layers. Electrical conductivity measurements indicated major defects in CaAl_(12)O_(19) to be interstitial oxide ion and calcium ion on the conduction layers. Diffusion coefficients of oxide ion and calcium ion in CaAl_(12)O_(19) were determined between 1123 and 1823 K.