Measurement of iron self-diffusion in hematite single crystals by secondary ion-mass spectrometry (SIMS) and comparison with cation self-diffusion in corundum-structure oxides

Iron bulk self-diffusion coefficients were measured in FC2O3 single crystals using original methodology based on the utilization of 57 Fe stable isotope as iron tracer and depth profiling by secondary ion-mass spectrometry (SIMS). The iron self-diffusion coefficients were measured along and perpendicular to the c-axis, between 900 and 1100 degrees C, in an oxygen atmosphere. Along the c-axis, the coefficients can be described by D-parallel to c (cm(2)/s) = 5.2 x 10(6) exp[-510 (kJ/mol)/RT], and are close to reliable data, available in the literature, obtained by means of radioactive techniques. Perpendicular to the c-axis, D-perpendicular to c (cm(2)/s) = 83exp[-430 (kJ/mol)/RT], and the coefficients are smaller than coefficients along the c-axis. The data are compared with previously results of cation bulk self-diffusion in Cr2O3 and Al2O3 single crystals.