A series of Ti-doped diopsides were synthesised by flux growth in a boron-rich melt under low fO2 conditions. Following chemical characterisation by EMPA and nuclear reaction microanalysis, their crystal structures were refined by single crystal X-ray diffraction. The diopside samples were doped with increasing amounts of Ti, resulting in a coupled increase in Na and B. The tetrahedral Si is substituted by Ti4+ and B, whereas Mg is substituted by Ti3+ and Ti4+ in the M1 octahedron with simultaneous charge compensation by coupled substitution of Na for Ca in the M2 octahedron. The occurrences of Ti4+ in the tetrahedral site and Ti3+ in the M1 octahedron are in agreement with optical absorption studies performed on the same samples. The diopside framework is strongly influenced by the incorporation of Ti4+ and Ti3+, with the M1 and M2 sites becoming more distorted as the substitutions increase, accompanied by a decreasing distortion of the T-site and the T-chain and an increase of the c lattice parameter.

Crystal chemistry of Ti3+-Ti4+-bearing synthetic diopsides

MOLIN, GIANMARIO;DAL NEGRO, ALBERTO
2004

Abstract

A series of Ti-doped diopsides were synthesised by flux growth in a boron-rich melt under low fO2 conditions. Following chemical characterisation by EMPA and nuclear reaction microanalysis, their crystal structures were refined by single crystal X-ray diffraction. The diopside samples were doped with increasing amounts of Ti, resulting in a coupled increase in Na and B. The tetrahedral Si is substituted by Ti4+ and B, whereas Mg is substituted by Ti3+ and Ti4+ in the M1 octahedron with simultaneous charge compensation by coupled substitution of Na for Ca in the M2 octahedron. The occurrences of Ti4+ in the tetrahedral site and Ti3+ in the M1 octahedron are in agreement with optical absorption studies performed on the same samples. The diopside framework is strongly influenced by the incorporation of Ti4+ and Ti3+, with the M1 and M2 sites becoming more distorted as the substitutions increase, accompanied by a decreasing distortion of the T-site and the T-chain and an increase of the c lattice parameter.
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2450649
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus ND
  • ???jsp.display-item.citation.isi??? 8
social impact