Electronic structure, orbital symmetry transformation, charge transfer, and valence state studies on Fe3+ - substituted CaCu3Ti4O12 quadruple perovskites using X-ray photoelectron spectroscopy

Urmila M. Meshiya, Pooja Y. Raval, Pooja R. Pansara, Monika Nehra, Narendra Jakhar, Sandeep Kumar, Kunal B. Modi, Dong Kwon Lim, Rishi Kumar Singhal

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

Here, we report a detailed study on electronic structure of quadruple perovskite system, CaCu3-xTi4-xFe2xO12 (x = 0.0, 0.1, 0.3, 0.5 and 0.7), using the powerful X-ray photoelectron spectroscopy (XPS). The Ca2p and Ti2p XPS spectra indicate that Ca and Ti ions exist in the divalent and tetravalent state, respectively, and no visible change is observed in their valence states on Fe3+-substitution (x). The asymmetrically shaped peaks of Ti2p3/2 infer the significant orbital hybridization of Ti atoms with other metallic cations like Cu and Fe, i.e. the Ti2p-Cu3d-Fe3d mixed states, which shows an increment with the Fe3+-content. The spectra also indicate that the Fe-substitution causes an increase in the strength of CuFe3d-O2p hybridization while weakening the strength of TiFe3d-O2p orbital hybridization. The Cu2p spectra suggest that Cu ions exist in two valence states i.e. the Cu2+ and Cu3+ out of which Cu2+ is dominant. The XPS results show clear evidence of charge transfer amongst Ti–Cu ions and evolution of n-type charge carriers. The O1s XPS spectra indicate anti-bonding states of t2g and eg type molecular orbitals separated by an energy separation of ~1.6 eV. A systematic relative change in the intensity of t2g and eg peaks with Fe-substitution point towards a clear transformation of symmetry of the system from TiO6 octahedral to the square-planar.

Original languageEnglish
Pages (from-to)2147-2154
Number of pages8
JournalCeramics International
Volume46
Issue number2
DOIs
Publication statusPublished - 2020 Feb 1

Bibliographical note

Funding Information:
Sandeep Kumar thanks HSCST, Government of Haryana, India (research grant vide letter No. HSCST/R & D/2018/2103 dated 01-08-2018) and DST-PURSE sanctioned to GJUS & T, Hisar under PURSE program No. SR/PURSE Phase 2/40 (G). Authors (PYR and KBM) want to convey appreciation to Dr. S. D. Gupta, Dr. S. & S.S. Ghandhy government engineering college, Surat, India for his technical help to provide crystal structures.

Funding Information:
Sandeep Kumar thanks HSCST , Government of Haryana, India (research grant vide letter No. HSCST/R & D/2018/2103 dated 01-08-2018) and DST-PURSE sanctioned to GJUS & T, Hisar under PURSE program No. SR/PURSE Phase 2/40 (G). Authors (PYR and KBM) want to convey appreciation to Dr. S. D. Gupta, Dr. S. & S.S. Ghandhy government engineering college, Surat, India for his technical help to provide crystal structures.

Publisher Copyright:
© 2019 Elsevier Ltd and Techna Group S.r.l.

Keywords

  • Calcium-copper-titanate
  • Electronic structure
  • Orbital symmetry transformation
  • X-ray photoelectron spectroscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Process Chemistry and Technology
  • Surfaces, Coatings and Films
  • Materials Chemistry

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