Oxidation state, local structure distortion, and defect structure analysis of Cu doped α-MnO2 correlated to conductivity and dielectric properties

E. Hastuti, A. Subhan, P. Amonpattaratkit, M. Zainuri, T. Triwikantoro, S. Suasmoro*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Cu-doped MnO2 with the composition of Mn1-xCuxO2 (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-MnO2 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 Mn3+ and Mn4+, while the copper is mainly attributed to Cu2+ and Cu3+ respectively. The small ionic size and highly oxidized Cu3+ substitute Mn4+, while Cu2+ substitutes Mn3+ or simultaneously with the larger K+ incorporated in the tunnel. Accordingly, the defects to exist in the sample, namely CuMn, MnMn, VO••, and e. Electrical characterization at room temperature revealed that the conductivity of Cu-doped MnO2 is dominated by electrons influenced by the various oxidation state of the cations in the octahedron sites, while space charges dominate the dielectric response.

Original languageEnglish
Article numbere11459
JournalHeliyon
Volume8
Issue number11
DOIs
Publication statusPublished - Nov 2022

Keywords

  • Defect structure
  • Doping
  • Local distortion
  • Manganese dioxide
  • Oxidation state

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