Synthetic and natural spinel single crystals having compositions approaching spinel end-members MgAl2O4, CoAl2O4, FeAl2O4, ZnAl2O4, MgCr2O4 and ZnCr2O4 were investigated by Raman spectroscopy in the 100-900 cm-1 range using the excitation of the blue 473.1 nm line of a diode pumped Nd:YAG laser. Each studied end-member exhibits a Raman fingerprint with at least one peculiar peak in terms of Raman shift and relative intensity. The chromates exhibit the A1g mode at 680 cm-1, more intense than the other modes and localized at lower frequencies than the aluminates, in agreement with the heavier atomic mass of Cr with respect to Al. For aluminate spinels the more intense and diagnostic peak in the spectrum is Eg at 405 cm-1 for MgAl2O4, F2g(2) at 516 cm-1 for CoAl2O4, F2g(3) at 660 cm-1 for ZnAl2O4 and A1g at 750 cm-1 for FeAl2O4. The discrimination between natural and synthetic spinels is quite successful. Synthetic spinels usually show high cation disorder which causes a broadening of the bands and the occurrence of a new peak at ca. 720 cm-1 with an A1g mode behavior, not predicted by the group theory.
Raman fingerprint of spinels / Andreozzi, Giovanni Battista; D'Ippolito, Veronica; P. P., Lottici; D., Bersani. - (2014). (Intervento presentato al convegno 21st General Meeting of the International Mineralogical Association tenutosi a Gauteng, South Africa nel 01-05/09/2014).
Raman fingerprint of spinels
ANDREOZZI, Giovanni Battista;D'IPPOLITO, VERONICA;
2014
Abstract
Synthetic and natural spinel single crystals having compositions approaching spinel end-members MgAl2O4, CoAl2O4, FeAl2O4, ZnAl2O4, MgCr2O4 and ZnCr2O4 were investigated by Raman spectroscopy in the 100-900 cm-1 range using the excitation of the blue 473.1 nm line of a diode pumped Nd:YAG laser. Each studied end-member exhibits a Raman fingerprint with at least one peculiar peak in terms of Raman shift and relative intensity. The chromates exhibit the A1g mode at 680 cm-1, more intense than the other modes and localized at lower frequencies than the aluminates, in agreement with the heavier atomic mass of Cr with respect to Al. For aluminate spinels the more intense and diagnostic peak in the spectrum is Eg at 405 cm-1 for MgAl2O4, F2g(2) at 516 cm-1 for CoAl2O4, F2g(3) at 660 cm-1 for ZnAl2O4 and A1g at 750 cm-1 for FeAl2O4. The discrimination between natural and synthetic spinels is quite successful. Synthetic spinels usually show high cation disorder which causes a broadening of the bands and the occurrence of a new peak at ca. 720 cm-1 with an A1g mode behavior, not predicted by the group theory.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
