Oxygen Vacancy Relaxation in Ca₃Co₄O_9+δ Ceramics

Abstract

Ca3Co4O9+δceramic powders were synthesized by the polymerized complex (PC) method. The same Ca3Co4O9+δceramic bar were treated in turn with three different processes of oxygen treatment: with no treatment, with oxydol (H2O2) treatment, and with N2treatment. Dynamic mechanical analysis (DMA) was performed from 123 to 623 K at rate of 1 K/min while the measuring frequencies are 0.05, 0.1, 0.25, 0.5, 1, 2, and 5 Hz. Two internal friction peaks are observed: one at the temperature range from 360 to 400 K (a broad peak, peak 1) and the other at around 390 K (a sharp peak, peak 2). Peak 2 is in correspondence with sudden metal-semiconductor transition (MST) near 400 K. Peak 1 is a kind of internal friction relaxation peak. For the sample with H2O2treatment and with no treatment, the activation energyHare 1.24 eV and 1.04 eV, respectively, and the preexponential factor τ0are 2.54×10-17sec and 7.82×10-15sec, respectively. We speculate that the mechanical relaxation process occurs in the Ca2CoO3subsystem of Ca3Co4O9+δ. The relaxation process for sample with no treatment is associated with the migration of OVs clusters in Ca2CoO3subsystem, and the relaxation process for the sample with H2O2treatment is associated with the migration of isolated OVs in Ca2CoO3subsystem.

Octahedral distortion due to oxygen vacancy reduction in La3+ modified BNT-BTO solid solutions near morphotropic phase boundary

“…However, at high temperatures, the oxygen vacancies actively take part in the conduction process due to their high mobility. From the calculation, it is found that the range of activation energy lies between 0.99-1.53 eV, which is comparable with the other perovskite-based compounds, as reported by different authors [61,57]. The above observations confirmed the increase in activation energy with the increase of La 3+ concentration in the composition.…”

Oxygen-vacancy-related relaxation and conduction behavior in (Pb1-xBax)(Zr0.95Ti0.05)O3 ceramics

“…43 The activation energy (E a ) is dependent on the concentration of OVs: E a = 0 eV for stoichiometric ABO 2.8 , 0.5 eV for ABO 2.9 , 1.0 eV for ABO 2.95 , and 2.0 eV for ABO 3 . 44,45 According to our results, activation energy increases with the increasing concentration of Ba 2+ , this successfully indicates that Ba 2+ doping can reduce the volatilization of Pb 2+ and restrict the generation of OVs. Based on the values of activation energy calculated from impedance, we can reasonably conclude that the relaxation observed in high temperature region was contributed to the short-range hopping of OVs, and the slight higher activation energy was due to low concentration of OVs.…”

The influence of oxygen vacancies on piezoelectricity in samarium‐doped Pb(Mg1/3Nb2/3)O3‐PbTiO3 ceramics

“…As the samples considered here were not processed at high oxygen partial pressure, we conclude that despite having been batched to favor A‐site vacancy compensation, the source of the reduction in conductivity of Sm‐doped sample (Figure 5) is oxygen vacancy annihilation. Also, the activation energy for oxygen ion conductivity in perovskites has been observed to increase with increasing oxygen occupancy within the range from 0.5 to 2.0 eV 37,38 . Hence both the decrease in σ 0 and small increase in E a suggest a decrease in oxygen vacancy concentration with the addition of Sm.…”