Convergent beam electron diffraction

Champness, P. E.

doi:10.1180/minmag.1987.051.359.04

Cited by 20 publications

(9 citation statements)

References 20 publications

(36 reference statements)

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“…1976; Champness, 1987). It is also potentially capable of demonstrating unambiguously whether or not a phase has a center of inversion and of identifying translational symmetry elements by observation of the extinction cross in kinematically-forbidden discs (Gjonnes and Moodie, 1965).…”

Section: •• Mel: Melilitementioning

confidence: 99%

A new titanium‐bearing calcium aluminosilicate phase: III. Crystals from a mixer furnace slag

Barber

Agrell

1994

Meteoritics

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Small crystals of an optically uniaxial Ti‐bearing calcium aluminosilicate were discovered in a mixer furnace slag consisting mostly of åkermanitic melilite. The crystals have the same unit cell as those observed for a phase crystallized from slowly‐cooled melts used to simulate the formation of aluminous inclusions in meteorites. Moreover, compositions of synthetic and meteoritic occurrences of the phase are all very similar and can be expressed in terms of a binary solid solution between the end‐members Ca3TiAl2Si3O14 and Ca3Ti(AlTi)(AlSi2)O14. Thus, crystallographic and crystallochemical information obtained from crystals in the mixer furnace slag can be used to constrain the origin of similar crystals found in meteoritic inclusions. We separated crystals from the mixer furnace slag by acid leaching; some were used for EPMA analysis, others were crushed for study by TEM methods or X‐ray powder diffraction. Convergent beam electron diffraction shows that the crystals belong to the trigonal (rhombohedral) class and have point group symmetry 3m. X‐ray powder diffraction gives the unit cell parameters a = 0.791 ± 0.009 nm, c = 0.492 ± 0.006 nm. The results suggest that the mineral has space group symmetry P3ml or P31m.

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Section: •• Mel: Melilitementioning

confidence: 99%

A new titanium‐bearing calcium aluminosilicate phase: III. Crystals from a mixer furnace slag

Barber

Agrell

1994

Meteoritics

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“…The next step was to obtain a CBED pattern corresponding to the three-fold axis in order to measure the radius of the first order Laue zone (FOLZ) ring. Its radius gives approximately the spacing of crystal planes in the direction of the zone axis along which the electron beam is directed according to the equation (e.g., Champness, 1987)…”

Section: General Observations By Atemmentioning

confidence: 99%

“…In the third paper of this series (Barber and Agrell, 1994), an occurrence of UNK from a furnace slag is described. Using CBED methods (Steeds, 1979;Williams, 1984;Champness, 1987), we establish that the space group of crystals. from the slag is either P3m1 or P31m; therefore, we use four-digit Miller-Bravais indices and hexagonal axes throughout this paper in describing the crystallography ofUNK.…”

Section: Introductionmentioning

confidence: 99%

A new titanium‐bearing calcium aluminosilicate phase: II. Crystallography and crystal chemistry of grains formed in slowly cooled melts with bulk compositions of calcium‐ aluminum‐rich inclusions

et al. 1994

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The crystallography and crystal chemistry of a new calcium‐titanium‐aluminosilicate mineral (UNK) observed in synthetic analogs to calcium‐aluminum‐rich inclusions (CAIs) from carbonaceous chondrites was studied by electron diffraction techniques. The unit cell is primitive hexagonal or trigonal, with a = 0.790 ± 0.002 nm and c = 0.492 ± 0.002 nm, similar to the lattice parameters of melilite and consistent with cell dimensions for crystals in a mixer furnace slag described by Barber and Agrell (1994). The phase frequently displays an epitactic relationship in which melilite acts as the host, with (0001)UNK | (001)mel and <10T0>UNK | <100>mel. If one of the two space groups determined by Barber and Agrell (1994) for their sample of UNK is applicable (P3ml or P31m), then the structure is probably characterized by puckered sheets of octahedra and tetrahedra perpendicular to the c‐axis with successive sheets coordinated by planar arrays of Ca. In this likely structure, each unit cell contains three Ca sites located in mirror planes, one octahedrally coordinated cation located along a three‐fold axis and five tetrahedrally coordinated cations, three in mirrors and two along triads. The octahedron contains Ti but, because there are 1.3–1.9 cations of Ti/formula unit, some of the Ti must also be in tetrahedral coordination, an unusual but not unprecedented situation for a silicate. Tetrahedral sites in mirror planes would contain mostly Si, with lesser amounts of Al while those along the triads correspondingly contain mostly Al with subordinate Ti. The structural formula, therefore, can be expressed as with Si + Ti = 4. Compositions of meteoritic and synthetic Ti‐bearing samples of the phase can be described in terms of a binary solid solution between the end‐members Ca3TiAl2Si3O14 and Ca3Ti(AlTi)(AlSi2)O14. A Ti‐free analog with a formula of Ca3Al2Si4O14 synthesized by Paque et al. (1994) is thought to be related structurally but with the octahedral site being occupied by Al, that is

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“…Figure 1 shows a comparison between conventional transmitted electron microscopy ͑TEM͒ and CBED. [14][15][16] In conventional TEM, a parallel beam is used to illuminate the specimen and the diffraction pattern consists of sharp spots. On the other hand, in CBED, a convergent beam is used to illuminate the specimen and the diffraction pattern consists of disks.…”

Section: Introductionmentioning

confidence: 99%

Effect of heavy boron doping on the lattice strain around platelet oxide precipitates in Czochralski silicon wafers

Yonemura

Sueoka

Kamei

2000

Journal of Applied Physics

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Effect of oxygen precipitates and induced dislocations on oxidation-induced stacking faults in nitrogen-doped Czochralski siliconThe effect of heavy boron doping on local lattice strain around platelet oxide precipitates in Czochralski silicon wafers was investigated quantitatively by convergent beam electron diffraction ͑CBED͒. Lightly boron doped (p Ϫ ) polished wafers, including platelet precipitates with density of about 5ϫ10 9 /cm 3 and with an edge length of about 500 nm, were prepared with an isothermal annealing at 800°C for 700 h. Heavy boron doped (p/ p ϩ ) epitaxial wafers, including an almost equal precipitate density and length to p Ϫ wafers, were also prepared with an isothermal annealing at 800°C for 200 h. It was found by strain analysis from high-order Laue zone patterns in the CBED disk that ͑i͒ the type of lattice strain was coincident in p Ϫ and p/ p ϩ wafers: the strain along the normal direction of the platelet precipitate was compressive, while the strain along the parallel direction of the platelet was tensile; ͑ii͒ the strain in p/p ϩ wafers was smaller than that in p Ϫ wafers; and ͑iii͒ the punched-out dislocations were generated by platelets only in p Ϫ wafers. The results of ͑ii͒ and ͑iii͒ indicate that the strain around the platelets is relaxed due to the heavy boron doping.

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Convergent beam electron diffraction

Cited by 20 publications

References 20 publications

A new titanium‐bearing calcium aluminosilicate phase: III. Crystals from a mixer furnace slag

A new titanium‐bearing calcium aluminosilicate phase: III. Crystals from a mixer furnace slag

A new titanium‐bearing calcium aluminosilicate phase: II. Crystallography and crystal chemistry of grains formed in slowly cooled melts with bulk compositions of calcium‐ aluminum‐rich inclusions

Effect of heavy boron doping on the lattice strain around platelet oxide precipitates in Czochralski silicon wafers

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