A Transmission Electron Microscope Study of Amethyst and Citrine

McLaren, A. C.; Phakey, P. P.

doi:10.1071/ph650135

Cited by 94 publications

(18 citation statements)

References 2 publications

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“…This defect can form as a result of beam damage in quartz, by dissociation of strained Si-O bonds (Devine 1990;Stevens Kalceff and Phillips 1995). In TEM, localised electron beam damage at dislocations, Brazil twin boundaries and, to a lesser extent, Dauphiné twin boundaries are a commonly observed phenomenon and continued beam damage finally results in complete (local) amorphisation (Carter and Kohlstedt 1981;Cherns et al 1980;McLaren et al 1970;Comer 1972;McLaren and Phakey 1965). Similar damage caused by inelastic scattering of the incoming electrons also occurs in the SEM (Vigouroux et al 1985, Stevens Kalceff 2009 andreferences therein).…”

Section: Discussionmentioning

confidence: 84%

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

2016

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Section: Discussionmentioning

confidence: 84%

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

2016

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“…Unfortunately, these specimens became damaged t o some extent by the electron beam during observation [6] and this seriously limited the time available for tilting the specimen into various diffracting conditions. 3.…”

Section: Methodsmentioning

confidence: 99%

“…Recently McLaren and Phakey [6] developed a simple method of preparing thin specimens of quartz suitable for transmission electron microscopy and have used tbis technique to examine the defect structures of a number of quartz minerals [7, 8,91.…”

Section: Introdactionmentioning

confidence: 99%

Transmission Electron Microscope Study of Brazil Twins and Dislacations Experimentally Produced in Natural Quartz

McLaren¹,

Retchford²,

Griggs³

et al. 1967

Physica Status Solidi (b)

127

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(a), J. A. RETCHFORD (a), I). T. GRINS (b), and J. M. CHBISTIE (b)Transmission electron microscopy haa been used to examine single crystals of natural quartz which have been plastically deformed in compression at high temperature (500 to 700 "C) and confining pressure (15 to 20 kbar) with high shear stress on (Oool). I n specimens deformed at 500 "C, the only features found are closely spaced pairs of planar defects parallel to (0001 }. Study of the diffraction contrast fringes reveals that each pair of defects bounds a Brazil twin band which has been produced by the high shear stress. At tho higher temperature there are dislocations in the twin bands and other regions of the crystals Eith disloeaticns only. The dislocations are almost invariably either pure screw ( b = a <1120>) or of a particular mixed character (predominantly edge, but with a 30" screw component). Arrays of the mixed dislocations are observed which would produce stress fields consistent with the stress-optical effects observed by optical microscopy.Eloktronenmikroskopische Durchstrahlungsmcthoden werden zur Untersuchung von natiirlichen Quarzeinkristallen benutzt, die in Kompression bei hohen Temperaturcn (600 bis 700 "C) im Druckbereich 15 bis 20 kbar mit hoher Schubspannung auf (OOO1) plastisch deformiert wurden. I n Proben, die bei 500 "C verformt wurden, sind die einzigen Merkmale eng beieinander liegende Paare von ebenen Defekten parallel zu (0001). Eine Untersuchung der Beugungskontrastbilder zeigt, dal3 jedes Defektpaar ein Zwillingsband vom Brazil-Typ begrenzt, das durch die hohe Schubspannung erzeugt wurde. Bei den hoheren Temperaturen findet man Versetzungen in den Zwillingsbandern und andere Kristallbereiche, die nur Versctzungen enthalten. Die Versetzungen sind meist gleichbleibend von reinem Schrauben-(b = a(1120)) oder von einem speziell gemischten Charakter (hauptsachlich Stufencharakter aber mit einem 30" Schraubenanteil). Anordnungen der gemischten Versetzungen werden beobachtet, die Spannungsfelder hervorrufen konnton in Ubereinstimmung mit dem spannungsoptischen Effekten, die lichtmikroskopisch beobechtet werden. Int,rodactionEarly experimental investigations of the mechanical deformation of quartz showed that it fractures in a brittle manner without evidence of plastic flow [l]. However, it is well known that high (hydrostatic) confining pressure tends to inhibit the fracture of materials thus enhancing the possibility of producing plastic deformation. In view of this Christie, Heard, and La Mori [2] attempted to deform quartz plastically at confining pressures in the region of 25 to 30 kbar at room temperature. In all experiments the quartz fractured as it does at lower confining pressures.

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“…I n view of the increasing interest in olivine type structures, a transmission electron microscope study has been made of defects in alexandrite. Samples suitable for transmission electron microscopy were made from gem-quality single crystals of yellow chrysoberyl and alexandrite, both natural and synthetic, using a technique previously described [ 7 ] .…”

Section: Introductionmentioning

confidence: 99%

Transmission Electron Microscope Study of Anti‐Phase Boundaries in Alexandrite (Al_2−xCr_xBeO₄)

Phakey

1969

Physica Status Solidi (b)

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A study has been made of the diffraction contrast fringe patterns observed by transmission electron microscopy in alexandrite (A12 -sCrZBe04), the chromium bearing variety of chrysoberyl. Evidence is presented that the fringe patterns are due to anti-phase boundaries resulting from faults in the cation stacking within the same oxygen lattice. Models for the probable ionic configuration of such boundaries are proposed and discussed. It is shown that the diffraction contrast fringe patterns observed with different operating reflections are consistent with those expected from the proposed models.Es wurden Beugungskontraststreifenbilder untersucht, die durch Transmissionselektronenmikroskopie in Alexandrit (A12 -&r,BeO,), die Chrom enthaltende Variante des Chrysoberyll, beobachtet wurden. Es wird bewiesen, da13 die Streifenbilder durch Antiphasengrenzen hervorgerufen werden, die von Fehlern der Kationenstapelung innerhalb desselben Sauerstoffgitters stammen. Modelle fur eine mogliche Ionenkonfiguration solcher Grenzen werden vorgeschlagen und diskutiert. Es wird gezeigt, da13 die Beugungskontraststreifenbilder, die mit unterschiedlichen Arbeitsreflexionen beobachtet wurden, mit denen ubereinstimmen, die fur die vorgeschlagenen Modelle erwartet werden. ' 52 physlca 32/2

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A Transmission Electron Microscope Study of Amethyst and Citrine

Cited by 94 publications

References 2 publications

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

Transmission Electron Microscope Study of Brazil Twins and Dislacations Experimentally Produced in Natural Quartz

Transmission Electron Microscope Study of Anti‐Phase Boundaries in Alexandrite (Al_2−xCr_xBeO₄)

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A Transmission Electron Microscope Study of Amethyst and Citrine

Cited by 94 publications

References 2 publications

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

Transmission Electron Microscope Study of Brazil Twins and Dislacations Experimentally Produced in Natural Quartz

Transmission Electron Microscope Study of Anti‐Phase Boundaries in Alexandrite (Al2−xCrxBeO4)

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Transmission Electron Microscope Study of Anti‐Phase Boundaries in Alexandrite (Al_2−xCr_xBeO₄)