Premium
Structural transformation in Ni‐bearing Na 2 Si 2 O 5 glass and melt
Author(s) -
Farges F.,
Brown G. E.,
Calas G.,
Galoisy L.,
Waychunas G. A.
Publication year - 1994
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl01079
Subject(s) - x ray absorption fine structure , xanes , materials science , coordination number , crystallization , analytical chemistry (journal) , absorption spectroscopy , nickel , non blocking i/o , spectroscopy , spectral line , mineralogy , metallurgy , geology , chemistry , optics , ion , biochemistry , physics , organic chemistry , chromatography , quantum mechanics , astronomy , catalysis
The coordination environment around Ni at minor concentration levels (2 wt. % NiO) in Na 2 Si 2 O 5 glass and melt (293–1250K) has been investigated by Ni K‐edge X‐ray Absorption Fine Structure (XAFS) spectroscopy. X‐ray Absorption Near Edge Structure (XANES) spectra indicate that both IV Ni and V Ni occur in the glass, whereas IV Ni is dominant in the melt. The average anharmonic Ni‐O distances derived from XAFS spectra of the glass at 293 K and the melt above 1150 K are 2.00 (±0.02) and 1.97 (± 0.02) Å, respectively. The Ni‐O distance in the glass is consistent with a mixture of IV Ni and V Ni, whereas that in the melt is consistent with dominantly IV Ni, suggesting a Ni‐coordination change during glass melting. This major change in Ni coordination indicates significant reorganization of the melt during quenching and crystallization. These observations for a compositionally‐simple melt/glass system may help explain the enrichment of Ni in early‐formed igneous minerals. They also suggest the possibility of a pressure‐induced coordination change around Ni in the mantle which may influence geochemical modeling of the deep Earth.