Oxygen pipe diffusion in sapphire basal dislocation

The oxygen self-diffusion behavior in deformed sapphire single crystals (alpha-Al2O3 sapphire) with a high density of unidirectional basal dislocations was examined in the temperature range of 1424-1636 degrees C using O-18 isotopes and secondary ion mass spectrometry-depth profiling techniques. The pipe and lattice diffusion kinetics were best described by r(2) D-P = 4.6 x 10(-20) exp (- 4.8[eV]/kT) [m(4)/s] and D-1 = 2.9 x 10(-1) exp (- 5.5[eV]/kT) [m(2)/s], respectively. Both the magnitude of pre-exponential factor and activation energy for oxygen pipe diffusion were in good agreement with that of indirect measurements of pipe diffusion deduced from the annihilation of dislocation dipoles. The measured bulk diffusion coefficient is also in good agreement with previously reported data having activation energies ranged between 5.5-6.1 eV.