Oxidation state, local structure distortion, and defect structure analysis of Cu doped α-MnO(2) correlated to conductivity and dielectric properties

Cu-doped MnO(2) with the composition of Mn(1-x)Cu(x)O(2) (x = 0–0.15) was synthesized and characterized. The synthesis was carried out by hydrothermal method at 140 °C for 5 h of reaction dwell time. The characterizations include X-Ray Diffraction (XRD), Microscopy, X-ray Absorption Spectroscopy (XAS), and Impedance complex analysis. It was revealed that all samples have nanorod morphology. Their size increases with the increasing dopant. Additionally, K ions are detected by EDX. All samples pose α-MnO(2) type structures performing (2 × 2) and (1 × 1) tunnels permitting large ions incorporated and oxygen deficiency. The octahedron was distorted to elongate up to x = 0.10, then compressed for x = 0.15, inducing the Jan Teller effect. Oxidation state analysis revealed that the manganese has Mn(3+) and Mn(4+), while the copper is mainly attributed to Cu(2+) and Cu(3+) respectively. The small ionic size and highly oxidized Cu(3+) substitute Mn(4+), while Cu(2+) substitutes Mn(3+) or simultaneously with the larger K(+) incorporated in the tunnel. Accordingly, the defects to exist in the sample, namely [Formula: see text] , [Formula: see text] , [Formula: see text] , and [Formula: see text]. Electrical characterization at room temperature revealed that the conductivity of Cu-doped MnO(2) is dominated by electrons influenced by the various oxidation state of the cations in the octahedron sites, while space charges dominate the dielectric response.