“…At higher Ti doping levels, the unit cell expands, which is suggestive of the reduction of Ti 4+ to the larger Ti 3+ . Based on a charge compensation model, 31,32 Ti 4+ ions in CFO will replace Fe 3+ ions in a 3 : 4 ratio with one negatively charged metal cation vacancy
and three positively charged defects
being generated in adjacent locations. Furthermore, negatively charged vacancies can provide electrons to positively charged defects, and result in the reduction of Ti 4+ ions to Ti 3+ .…”