ARC-fusion growth and characterization of high-purity MgO crystals

Butler, Charles; Sturm, B.; Quincy, Roger B.

doi:10.1016/0022-0248(71)90142-4

Cited by 55 publications

(10 citation statements)

References 8 publications

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“…We refer to the powders as a container wall material, which decreases the chance of contamination of the melt by the outer powders and reduces operating costs. In the experimental process, three graphite electrodes with different currents are applied according to the experimental requirement, which is different from that of Butler et al [7]. The disturbance of the temperature field is reduced by maintaining a constant voltage (e.g., 50 V) for a long time (20 h), which is advantageous to growing high-quality MgO single crystals with large and super-large sizes.…”

Section: Resultsmentioning

confidence: 99%

“…Butler et al [7] investigated the possibility of producing MgO single crystals that were purer and clearer than those previously available and found that developed methods could produce high-purity MgO single crystals, which were typically 1-3 cm in diameter, and 4-6 cm in length. Most of them weighed 50-100 g, some even weighed 300 g or more.…”

Section: Introductionmentioning

confidence: 98%

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Growth of large MgO single crystals by an arc-fusion method

Zhang

Xue

et al. 2005

Journal of Crystal Growth

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Growth of large MgO single crystals by an arc-fusion method

Zhang

Xue

et al. 2005

Journal of Crystal Growth

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“…The quantity C total depends on the grain size and is a steep function of temperature. Then C bulk is on the order of 2% around 3000 K, the crystallization temperature of MgO (Butler et al 1971). Upon cooling to 300 K, assuming equilibrium could be maintained, C bulk decreases by 6 orders of magnitude to about 0.01 ppm.…”

Section: A5 Grain Size Effectsmentioning

confidence: 99%

“…The difference in mean chain length of the carboxylic acids is consistent with the difference in the CH intensities in Figure 1, i.e., average CH 2 /CH 3 ratios of 8:1 in MgO and 10-12:1 in olivine. The MgO crystals, grown in the laboratory from an MgO melt, had cooled within a few hours (Butler et al 1971). The olivine crystals have cooled much more slowly, over thousands of years, in the conduit of a failed volcanic eruption (Frey & Prinz 1978).…”

Section: Càh Bonds In Mgo and Olivv Ine Singg Le Crystalsmentioning

confidence: 99%

Solid Solution Model for Interstellar Dust Grains and Their Organics

Freund

2006

ApJ

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We present a dust grain model based on the fundamental principle of solid solutions. The model is applicable to the mineral (silicate) component of the dust in the interstellar medium (ISM ). We show that nanometer-sized mineral grains, which condense in the gas-rich outflow of late-stage stars or expanding gas shells of supernova explosions, do not consist of just high melting point oxides or silicates. Instead they form solid solutions with gas-phase components H 2 O, CO, and CO 2 that are omnipresent in environments where the grains condense. Through a series of thermodynamically well-understood solid-state processes, these solid solutions become ''parents'' of organic matter that precipitates inside the grains. Thus, the mineral dust grains and their organics become part of the same thermodynamically defined solid phase and, hence, physically inseparable. This model can account for many astronomical observations, which no prior model can adequately address, specifically: (1) Organics in the diffuse ISM are identified by a 3.4 m IR band, characteristic of aliphatic hydrocarbons composed of ÀCH 2 À and of ÀCH 3 groups. (2) The methylene-to-methyl ratio is nearly constant, implying a CH 2 :CH 3 ratio of $5:2. (3) The intensity ratio between the 9.7 and the 3.4 m band is nearly constant, implying a silicate-to-organics ratio of $10:1. (4) In dense clouds the complex 3.4 m band is replaced by a weak, featureless 3.47 m band. (5) Whereas silicate grains identified by their 9.7 m band tend to align in magnetic fields, grains with a strong 3.4 m organic signature do not tend to align.

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“…Valuable information was obtained through follow-on single crystal studies of the electrical conductivity [Kathrein and Freund, 1983], thermal expansion [Wengeler and Freund, 1980], magnetic susceptibility [Batllo et al, 1991], electron spin resonance [Kathrein et al, 1984], dielectric polarization [Freund et al, 1993], refractive index [Freund et al, 1994], and most recently muon spin relaxation [unpublished results]. These additional investigations have provided irrefutable evidence that, despite their provenance from the extremely highly reducing conditions of a carbon arc fusion furnace [Abraham et al, 1971;Butler et al, 1971], the MgO crystals contain peroxy defects and evolve H 2 gas [Freund et al, 2002].…”

Section: Redox Conversion Of Oh -Pairs To Peroxy Plus Hmentioning

confidence: 99%

Paradox of peroxy defects and positive holes in rocks. Part I: Effect of temperature

Freund

2015

Journal of Asian Earth Sciences

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a b s t r a c tMost non-seismic, non-geodesic pre-earthquake phenomena are believed to be controlled by the stress-activation of peroxy defects in rocks, which release highly mobile electric charges. Though ubiquitous in minerals of igneous and high-grade metamorphic rocks, peroxy defects have been widely overlooked in the past. The charge carriers of interest are positive holes, chemically equivalent to O À in a matrix of O 2À , physically defect electrons in the O 2À sublattice, highly mobile, able to propagate fast and far. O À are oxidized relative to O 2À . As such O À are not supposed to exist in minerals and rocks that come from deep within the Earth's crust, where the environments are overwhelmingly reduced. The presence of O À appears to contradict thermodynamics. However, there is no conflict. In order to understand how peroxy defects are introduced into common rock-forming minerals, over which temperature window they release positive holes, and how this may be related to pre-earthquake phenomena, we look at peroxy defects in a crystallographically and compositionally well characterized model system: single crystals of nominally high-purity MgO, grown from the melt under highly reducing conditions. During crystallization the MgO crystals incorporate OH À through dissolution of traces of H 2 O in the MgO matrix, leading to a solid solution (ss) Mg 1Àd (OH) 2d O 1À2d , where d ( 1. During cooling, the ss leaves thermodynamic equilibrium, turning into a metastable supersaturated solid solution (sss). Using infrared (IR) spectroscopy it is shown that, during further cooling, OH À pairs at Mg 2+ vacancy sites rearrange their electrons, undergoing a redox conversion, which leads to peroxy anions, O 2 2À , plus molecular H 2 . Being diffusively mobile, the H 2 molecules can leave the Mg 2+ vacancy sites, leaving behind cation-deficient Mg 1Àd O. During reheating, but in the sss range, the O 2 2À break up, releasing positive hole charge carriers, which profoundly affect the electrical conductivity behavior. In igneous mafic and ultramafic rocks, similar changes in the electrical conductivity are observed in the temperature window, where peroxy defects of the type O 3 Si-OO-SiO 3 break up. They release positive holes, which control the electrical conductivity response. Deciphering these processes helps understanding the stress-activation of positive holes along the geotherm.

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ARC-fusion growth and characterization of high-purity MgO crystals

Cited by 55 publications

References 8 publications

Growth of large MgO single crystals by an arc-fusion method

Growth of large MgO single crystals by an arc-fusion method

Solid Solution Model for Interstellar Dust Grains and Their Organics

Paradox of peroxy defects and positive holes in rocks. Part I: Effect of temperature

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