Synthesis, optical properties and conduction mechanism study of α- and γ-NaMnO₂ materials

Abstract

NaMnO2, in both α and γ phases, cathode active materials are synthesized by the solid-solid method. X-ray powder diffraction analysis revealed that these compounds crystallize in the monoclinic with C2/m...

Investigation of optical, dielectric, and conduction mechanism in lead-free perovskite CsMnBr3

“…11b , as presented, the increase in temperature leads to an increase in the values of s 1 while the value of s 2 decreases which suggest that the short motion of charge carriers dominates as the temperature increase. 30 The temperature behavior of s 1 is typically to that proposed by the non-small polaron tunneling model, for which the conductivity is given by the following expression: 31 where α −1 (Å) is the spatial extension of the polaron, τ 0 represents the characteristic relaxations time, whose value is in the order of an atom vibrational period (10 −13 s), N EF is the density of states near the Fermi level and R ω is the tunneling distance given by the expression: where ω H is the energy of polaron hopping. The power exponent is given by the expression: …”

Study of alternative current conduction mechanisms on the -LiFeO 2 - Based solid electrolyte

“…Additionally, the stretching vibration of the LiO6 band is represented by the peaks detected at 867, 957 and 987 cm −1 . The peaks observed at 997 and 1063 cm -1 can be attributed to the 4 deformation mode of the FeO6 group [21,22].…”

“…Where R is the reflectance and e is the thickness of the compound (e=1mm), the term (F (R)/e) is proportional to the absorption coefficient (α). To calculate Eg, we used the modified Kubelka -Munk equation which corresponds to a direct electronic transition: By comparison with other similar lamellar type compounds, the gap energy of the LiFeO2 compound is of the same order as that of the LiMnO2 compound (Eg = 1.93 eV) [23], LiCoO2 (Eg = 2.15 eV) [24] and LiCo0.7Mn0.3O2 (Eg = 1.88 eV) [25] yet it is lower than that of the soduim-based compounds like NaMnO2 (Eg = 4.96 eV) [22] and the NaCu0.2Fe0.8-xMnxO2 series (2.8e V <Eg< 3 eV) [26]. The obtained band gap value of LiFeO2 compound is within range of the band gap of the semiconductors that are utilized in several applications in the optoelectronic field.…”