Study of Crystallisation of Yttrium Garnets Y3R5O12(R = Al, Ga) by High Temperature EXAFS

Launay, X; Landron, C.; Coutures, Jean-Pierre; Bazin, Dominique

doi:10.1051/jp4:19972220

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“…The use of CO/CO 2 and N 2 /air gas mixtures to control f O 2 at temperatures up to $1500 K has also been reported (Hoser et al, 1995;Hilbrandt & Martin, 1999). In some designs a vacuum or inert gas is required to prevent oxidation of the furnace heating element (Farges et al, 1995;Filipponi et al, 2000); metals such as Ir, W and Ta can be used to achieve temperatures in excess of 3300 K. Reactive samples can be supported without contact by both electromagnetic and gas¯ow levitation (Jacobs et al, 1996;Launay et al, 1997). High pressures in conjunction with high temperatures have been achieved using autoclave, Paris±Edinburgh and diamond-anvil type cells [see Filipponi (2001) for a review].…”

Section: Introductionmentioning

confidence: 99%

A furnace design for XANES spectroscopy of silicate melts under controlled oxygen fugacities and temperatures to 1773 K

et al. 2003

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A controlled-atmosphere furnace has been constructed for X-ray absorption spectroscopy experiments under imposed oxygen fugacities at temperatures up to 1773 K. The use of the furnace is demonstrated in a study of the oxidation state of Cr in a basaltic silicate melt (mid-ocean ridge basalt) by K-edge XANES spectroscopy. This is the first time the Cr(2+)/Cr(3+) ratio has been identified directly in an Fe-bearing melt. At typical terrestrial oxygen fugacities around half the Cr is present as Cr(2+), even though this oxidation state has never been identified in a terrestrial material and only Cr(3+) is observed after quenching to a glass. Cr(2+) oxidizes to Cr(3+) on cooling in the presence of Fe(3+) according to the electron exchange reaction Cr(2+) + Fe(3+) --> Cr(3+) + Fe(2+). This illustrates the importance of the in situ determination of metal oxidation states in melts.

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