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

Cu-doped MnO with the composition of MnCuO (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 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 and Mn, while the copper is mainly attributed to Cu and Cu respectively. The small ionic size and highly oxidized Cu substitute Mn, while Cu substitutes Mn or simultaneously with the larger K incorporated in the tunnel. Accordingly, the defects to exist in the sample, namely , , , and . Electrical characterization at room temperature revealed that the conductivity of Cu-doped MnO is dominated by electrons influenced by the various oxidation state of the cations in the octahedron sites, while space charges dominate the dielectric response.