Intrinsic Co4+/Co2+ defect formation in late members of the perovskite rare earth metal cobaltate oxide series as evidenced by dielectric relaxation measurements

The ac dielectric response of GdCoO3 and HoCoO3 was investigated. Dielectric relaxations were observed in the imaginary part of the electric modulus M″ for both compounds. The relaxation times obeyed an Arrhenius relationship in HoCoO3, whereas they did not in GdCoO3. The behavior has been discussed in terms of polaron hopping accompanying the Co4+ species, suggesting the electrical transport mechanism to be similar to that in LaCoO3. The calorimetric relevance to the rearrangement of the polaron in HoCoO3 has also been referred to as compared to that in GdCoO3 and LaCoO3.