Precipitation in non-stoichiometric spinel

Donlon, W. T.; Mitchell, T. E.; Heuer, A. H.

doi:10.1007/bf00752251

Cited by 32 publications

(21 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Extensive characterization of defect spinels with varying compositions over the last 50 years has demonstrated that thermal stability is markedly reduced compared to stoichiometric spinel (e.g. Donlon et al, 1982;Saalfeld and Jagodzinski, 1957;Viertel and Seifert, 1979;Wang, 1969). At high temperatures, non-stoichiometric spinels precipitate their excess alumina as a-Al 2 O 3 , resulting in the formation of a stoichiometric spinel host with alumina lamellae.…”

Section: Stability Of Defect Spinelmentioning

confidence: 98%

“…As such, the possibility of alumina precipitation during high-temperature/pressure experiments performed here needs to be considered. Donlon et al (1982) investigated alumina precipitation in single crystals of defect spinel at temperatures up to 1300°C and concluded that alumina precipitation in single crystals is suppressed due to the difficulty of nucleation. The most likely cause for suppression is the large strain energy associated with precipitation, which would result in a significant increase in volume.…”

Section: Stability Of Defect Spinelmentioning

confidence: 99%

See 1 more Smart Citation

Water incorporation in synthetic and natural MgAl2O4 spinel

Bromiley

Nestola

Redfern

et al. 2010

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

The solubility and incorporation mechanisms of water in synthetic and natural MgAl 2 O 4 spinel have been investigated in a series of high-pressure/temperature annealing experiments. In contrast to most other nominally anhydrous minerals, natural spinel appears to be completely anhydrous. On the other hand, non-stoichiometric Al-rich synthetic (defect) spinel can accommodate several hundred ppm water in the form of structurally-incorporated hydrogen. Infrared (IR) spectra of hydrated defect spinel contain one main O-H stretching band at 3343-3352 cm À1 and a doublet consisting of two distinct O-H bands at 3505-3517 cm À1 and 3557-3566 cm À1 . IR spectra and structural refinements based on single-crystal X-ray data are consistent with hydrogen incorporation in defect spinel onto both octahedral and tetrahedral O-O edges. Fine structure of O-H bands in IR spectra can be explained by partial coupling of interstitial hydrogen with cation vacancies, or by the effects of Mg-Al disorder on the tetrahedral site. The concentration of cation vacancies in defect spinel is a major control on hydrogen affinity. The commercial availability of large single crystals of defect spinel coupled with high water solubility and similarities in water incorporation mechanisms between hydrous defect spinel and hydrous ringwoodite (Mg 2 SiO 4 ) suggests that synthetic defect spinel may be a useful low-pressure analogue material for investigating the causes and consequences of water incorporation in the lower part of Earth's mantle transition zone.

show abstract

Section: Stability Of Defect Spinelmentioning

confidence: 98%

Section: Stability Of Defect Spinelmentioning

confidence: 99%

Water incorporation in synthetic and natural MgAl2O4 spinel

Bromiley

Nestola

Redfern

et al. 2010

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

show abstract

“…Compared with the stoichiometric spinel, non-stoichiometric spinel is also very common. B 2 O 3 oxide can dissolve into AB 2 O 4 to form B-rich non-stoichiometric spinel, AO·nB 2 O 3 (n > 1) [38]. Tetrahedral A 2+ ions can be substituted by B 3+ ions accompanied by the formation of cation vacancies.…”

Section: X-ray Diffraction (Xrd)mentioning

confidence: 99%

High-temperature steam reforming of methanol over ZnO–Al2O3 catalysts

Yang

Chen

2011

Applied Catalysis B: Environmental

View full text Add to dashboard Cite

“…For example, O-H absorption onto spinel (100) surfaces annealed in H 2 has been recently shown to differ considerably from O-H bulk incorporation [22], with O-H showing a high affinity for incorporation into alumina-rich (Mg-free) surface layers. Annealing of non-stoichiometric spinel at ambient pressure and the high temperatures used by Fukatsu et al [14] additionally promotes alumina precipitation, resulting in the penetration of reaction fronts into bulk crystals [26]. This precipitation reaction is not energetically favourable at high pressures due to the large lattice strain energy associated with alumina growth, and would be further suppressed in the present study by the lower annealing temperatures used.…”

Section: H + and D + Incorporation And Diffusivity In Non-stoichiometmentioning

confidence: 65%