Physics and Chemistry of Minerals

, Volume 45, Issue 5, pp 443–461 | Cite as

Co2+-doped diopside: crystal structure and optical properties

  • C. Gori
  • M. Tribaudino
  • F. Mezzadri
  • H. Skogby
  • U. Hålenius
Original Paper


Synthetic clinopyroxenes along the CaMgSi2O6–CaCoSi2O6 join were investigated by a combined chemical-structural-spectroscopic approach. Single crystals were synthesized by flux growth methods, both from Ca-saturated and Ca-deficient starting compositions. Single crystal structure refinements show that the incorporation of Co2+ at the octahedrally coordinated cation sites of diopside, increases the unit-cell as well as the M1 and the M2 polyhedral volumes. Spectroscopic investigations (UV–VIS–NIR) of the Ca-rich samples reveal three main optical absorption bands, i.e. 4 T 1g4 T 2g(F), 4 T 1g4 A 2g(F) and 4 T 1g4 T 1g(P) as expected for Co2+ at a six-coordinated site. The bands arising from the 4 T 1g4 T 2g(F) and the 4 T 1g4 T 1g(P) electronic transitions, are each split into two components, due to the distortions of the M1 polyhedron from ideal Oh-symmetry. In spectra of both types, a band in the NIR range at ca 5000 cm−1 is caused by the 4 A 2g4 T 1g(F) electronic transition in Co2+ in a cubic field in the M2 site. Furthermore, an additional component to a band system at 14,000 cm−1, due to electronic transitions in Co2+ at the M2 site, is recorded in absorption spectra of Ca-deficient samples. No variations in Dq and Racah B parameters for Co2+ at the M1 site in response to compositional changes, were demonstrated, suggesting complete relaxation of the M1 polyhedron within the CaMgSi2O6–CaCoSi2O6 solid solution.


Pyroxenes Crystal structure Cobalt UV–VIS–NIR Crystal field 



We thank Michael Taran and an anonymous reviewer for comments that helped to improve the paper.

Supplementary material

269_2017_932_MOESM1_ESM.doc (1.1 mb)
Supplementary material 1 (DOC 1099 KB)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2017

Authors and Affiliations

  1. 1.Department of Chemistry, Life Sciences and Environmental SustainabilityUniversity of ParmaParmaItaly
  2. 2.Department of GeosciencesSwedish Museum of Natural HistoryStockholmSweden

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