Dependence of oxygen diffusion in epitaxial YIG : Ca on defect concentration

Measurements of oxygen diffusion in YIG : Ca at different oxygen partial pressures have shown that the diffusion rate strongly depends on oxygen vacancy concentration. At very high vacancy concentration this diffusion is quite rapid. For example, with approximately 0.1 vacancies per formula unit the oxygen diffused 0.9 mm in 24 h at 325 °C. It has also been shown that under many conditions the rate limiting process occurs at the surface of the YIG : Ca. An additional thin epitaxial layer having a much higher defect concentration greatly reduces the limitations imposed by the surface.