Origin of the colossal dielectric properties in double-perovskite Sr2CoNbO6

Abstract

Sr2CoNbO6 ceramics were prepared via the solid-state reaction route. The dielectric properties of Sr2CoNbO6 ceramics were investigated as a function of temperature (90–330 K) in the frequency range from 20 Hz to 10 MHz. Our results reveal that the dielectric properties of Sr2CoNbO6 are closely linked with the conductivity of the sample. The conductivity is dominated by hopping localized carriers. The hopping process not only produces considerable conductivity followed the universal dielectric response behavior, but also gives rise to dipolar effects leading to the polaron relaxation in intermediate-temperature range. At low enough temperatures, the hopping process is frozen-in and the low-temperature Maxwell-Wagner relaxation due to frozen carriers featuring the nearly constant loss behavior appears. At higher temperatures, the long-distance transportation of the carriers becomes remarkable. These carriers are easily blocked by various interfaces resulting in space charge therein and the conventional Maxwell-Wagner relaxation in the high-temperature range. Our results demonstrate that a multirelaxation mechanism instead of a single relaxation underlies the colossal dielectric properties of Sr2CoNbO6

Structural, Dielectric, and Energy Storage Properties of Citric Acid and Ethylene Glycol Assisted Hydrothermally Synthesized Y2FeCoO6

“…The Y 2 FeCoO 6 has a higher value of ε r comparative to many other double perovskites such as La 2 FeCoO 6 , Sr 2 CoNbO 6 , Pr 2 CoTiO 6 , Po 2 CoZrO 6 , La 2 NiMnO 6 at room temperature, which makes it a useful material for electrochemical application. [ 8,9,11,39,40 ] The value of tan δ for Y 2 FeCoO 6 is almost similar to other double perovskites in high‐frequency range >1 kHz. However, this material has a large tangent loss in the low‐frequency and high‐temperature range in comparison to other similar compounds.…”

“…[ 3–7 ] Furthermore, the room temperature giant relative permittivity and low loss factor of such materials, viz., Ba 2 PrRuO 6 , La 2 MnCoO 6 , La 2 FeCoO 6 , Sr 2 CoNbO 6 , Ho 2 CdTiO 6 , Pr 2 CoTiO 6 , Y 2 CoMnO 6 make them very useful for energy storage application. [ 6,8–11 ]…”

Structural, transport, optical and electronic properties of Sr$_2$CoNbO$_6$ thin films

“…It has been reported that the Sr 2 CoNbO 6 and related compounds crystalize in cubic phase with the random occupancy of B-site cations i.e. perovskite unit cell with P m 3m space group [34,39,62], while others have shown the rhombohedral structure with R 3m space group [33] as well as octahedral tilted tetragonal structure with I4/m space group having a 0 a 0 c − Glazer notation i.e antiphase tilting of NbO 6 and CoO 6 octahedra along [001] direction [36][37][38]63]. It is well known that perovskites with ideal cubic structure (P m 3m with the random occupancy of B-site cations) is centrosymmetric and hence Raman inactive, while group theory predict four Raman active modes for cubic B-site ordered structure (F m 3m double perovskite structure, where unit cell doubles in all the three crystallographic directions) i.e.…”

“…The density functional theory (DFT) calculations within the generalized gradient approximation predict the semiconducting nature of the material with 0.2 eV band gap [38], which is supported by the positive temperature coefficient of conductivity carried out on bulk Sr 2 CoNbO 6 with an activation energy of 0.25-0.35 eV, where conductivity sensitively increase with the oxygen partial pressure at 973 K [35,40]. Wang et al showed the colossal dielectric properties in the compound, where the dielectric response was found to be closely related to the conduction mechanism governed by the hopping of localized charge carriers [36]. Electronic band structure can give a valuable information about the spin state of Co 3+ and hence the magnetic properties of Sr 2 CoNbO 6 as LS Co 3+ is insulating while IS/HS states are electrically conducting due to the presence of unpaired electrons.…”

“…In this context, Sr 2 CoNbO 6 is of particular interest due to its interesting structural, magnetic, transport and electronic properties and hence their wide range of applications [33][34][35][36][37][38][39][40]. However, a large discrepancy in the literature can be found regarding the effective magnetic moment and hence the spin states of Co 3+ in bulk Sr 2 CoNbO 6 .…”