Characterization of low-dislocation synthetic quartz grown on highly distorted seed by X-ray topography (original) (raw)
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New seed geometry for growth of low dislocation synthetic quartz
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
A method to grow low dislocation density synthetic quartz by using a special cutting seed geometry is reported. With this method, a relatively high dislocation density seed material is allowable. For such a purpose, a seed of new geometry was prepared and grown in a standard hydrothermal growth condition, long in Y-direction with multiple V-shaped notches made on Z-face. The characterization study was conducted by X-ray topography. The results showed new growth regions, equal to the numbers of V-shaped notches made in the seed and usually not found in the conventional Y-and Z-bar synthetic quartz crystals. Each new growth region is composed of two sectors of distinct textures. Soon they disappear due to their high growth velocity, and they are replaced by the so-called Z-region. However, the growth process of these new sectors grown perpendicular to the internal faces of the V-shaped notches played an important role in inhibiting the propagation of the dislocation originally present in the seed into the grown Z-region.
Materials Research-ibero-american Journal of Materials, 2004
In the present study, the morphology and the impurity distribution were investigated in growth sectors formed around the [0001] axis of synthetic quartz crystals. Plates containing cylindrical holes and cylindrical bars parallel to [0001] were prepared by ultrasonic machining and further used as seed-crystals. The hydrothermal growth of synthetic quartz was carried out in a commercial autoclave under NaOH solution during 50 days. The morphologies of crystals grown from cylindrical seeds were characterized by X-ray diffraction topography. For both types of crystals, +X- and X- growth sectors were distinctly observed. Infrared spectroscopy and ionizing radiation were adopted to reveal the distribution of point defects related to Si-Al substitution and OH-species. It was found a different distribution of Al-related centers in relation to the crystals grown from conventional Y-bar and Z-plate seeds.
High resolution X-ray Laue topography of thick quartz crystals at SPring-8
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
High resolution X-ray Laue topography was conducted on the SPring-8 BL-28B2 beamline, operating at a 5-100 keV energy range. The use of this beamline was particularly suitable for characterization of thick samples of giant blocks of natural quartz used as seeds for growing synthetic quartz; and also to understand the propagation mechanism of dislocation lines in synthetic quartz. Area enlargement of Laue topographs by scanning the sample-film stage in the vertical direction was particularly useful for high energy diffraction images, due to their relatively small vertical dimensions. The methodology applied to characterize thick crystals used in the present research, is an effective contribution to develop nearly perfect large dimension seeds and synthetic quartz bars for the next generation of ''surface acoustic waves'' device substrates.
Tectonophysics, 2006
Deformation experiments have been carried out to investigate the effect of dynamic recrystallisation on crystallographic preferred orientation (CPO) development. Cylindrical samples of natural single crystals of quartz were axially deformed together with 1 vol.% of added water and 20 mg of Mn 2 O 3 powder in a Griggs solid medium deformation apparatus in different crystallographic orientations with compression direction: (i) parallel to bcN, (ii) at 45°to bcN and 45°to baN and (iii) parallel to baN. The experiments were performed at a temperature of 800°C, a confining pressure of 1.2 GPa, a strain rate of ∼ 10 − 6 s − 1 , to bulk finite strains of ∼14-36%. The deformed samples were analysed in detail using optical microscopy, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Two different microstructural domains were distinguished in the deformed samples: (i) domains with undulatory extinction and deformation lamellae, and (ii) domains with new recrystallised grains. Within the domains of undulatory extinction, crystal-plastic deformation caused gradual rotations of the crystal lattice up to ∼30°away from the host orientation. New recrystallised grains show a strong CPO with c-axis maxima at ∼ 45°to the compression direction. This is the case in all experiments, irrespective of the initial crystallographic orientation. The results show that c-axes are not continuously rotated towards the new maxima. The new grains thus developed through a mechanism different from subgrain rotation recrystallisation. New grains have a subeuhedral shape and numerous microcavities, voids, fluid channels and fluid inclusions at their grain boundaries. No host control is recorded in misorientation axes across their large angle grain boundaries. New grains might have been created by nucleation from solution in the μm-scale voids and microfractures. The CPO most likely developed due to preferred growth of the freshly precipitated grains with orientations suitable for intracrystalline deformation at the imposed experimental conditions.
X-RAY TOPOGRAPHIC STUDY OF VACUUM SWEPT QUARTZ CRYSTALS
Aluminium is invariably present in both synthetic and natural quartz crystals which exists as a substitution for silicon. The trivalent aluminium can make only three of the bonds normally made by a silicon and hence a negative charge exists on the site due to the fourth non-bonding oxygen. This charge is compensated by impurity ions which are bound electrostatically in an adjacent *-axis channel. During sweeping the compensating impurity ions which are weakly bound near the aluminium atoms move toward the cathode. This result in the collection of negative space charges near the anode side of the crystal deforming the lattice. X-ray transmission topographs recorded from vacuum swept quartz crystals show a strong dark contrast near the anode side of the crystals due to lattice strain. This strong X-ray topographic contrast disappears when the crystals are subjected to prolonged X-ray irradiation. The negative charge formed near the anode side of the crystals during sweeping is compensated by forming aluminium-hole and aluminium-hydroxyl centres during the irradiation
A New X-ray Topographic Defect Contrast on Swept Quartz Crystals
X-ray topographic studies are made on vacuum-swept a-quartz crystals. A strong defect contrast is observed on X-ray topographs near the anode side of the crystal. This contrast disappears when the crystals are subjected to prolonged X-ray irradiation. The presence of this unusual contrast is attributed to lattice strains due to the collection of space charges near the anode side during vacuum sweeping. The negative space charge so formed is compensated by forming A1-OH and Al-hole centres during irradiation
Journal of Geophysical Research, 1984
A hydrothermally grown synthetic quartz crystal with 370 + 60 ppm hydroxyl impurity was cut into right rectangular prisms in eight crystallographic orientations. We compressed the prisms under constant axial force corresponding to a uniaxial stress of 140.0 + 0.5 MPa, and temperatures of 510 ø and 750øC. All but one of the samples sustained permanent axial strains of 2-3%. We established the operating slip systems from specimen shape change, slip bands and dislocation etch pits on polished surfaces, crystallographic orientation changes, stress optical features in thin sections, and transmission electron microscopy. The observed creep behavior and plasticity divided the samples into three groups'(1) Crystals compressed at 45 ø to [0001] and [2ii0] and those compressed 2_(01il) and 2_(0i11) deformed principally by slip parallel to [0001]. Creep rates were relatively high and were not strongly sensitive to test __ temperature. Dislocation arrays approximately parallel to (2110) are common. Dislocation loops are elongate parallel to [0001], indicating that the edge segments were more mobile than the screw segments. (2) The second g_roup of samples were loaded normal to [0001] in three orientations: 2_(2ii0), 2_(01i0), and at 45 ø to (1100). These samples deformed primarily by •10i0• (a) slip with some evidence for secondary slip on the other systems. They were more creep resistant than the first group and displayed a much higher sensitivity of creep rate to test temperature. Dislocation loops are very elongate parallel to [0001], indicating that the screw dislocation segments were much more mobile than the edge segments. (3) A sample compressed parallel to [0001] at 750øC crept at a barely detectable rate (~ 10-9 s-•) and no optical scale slip features were observed. These results confirm our earlier work on one orientation each from groups 1 and 2, which indicated a strong creep anisotropy for this same crystal. This creep anisotropy parallels a remarkably similar anisotropy in the diffusivity of impurities in quartz, suggesting a causal relationship between impurity diffusion and creep associated with hydrolytic weakening. INTRODUCTION Quartz crystals in nature can be remarkably pure. Total impurity concentrations in inclusion-free, colorless, and transparent vug-grown natural crystals rarely exceed 100 ppm [Frondel, 1962]. Natural transparent and colorless quartz has very high plastic yield strength even at elevated temperatures [Griggs and Blacic,
European Journal of Mineralogy, 2007
The crystallographic orientations of two sets of 3144 and 1660 straight segments of sutured quartz grain boundaries, formed during dynamic recrystallization and subsequent annealing at lower greenschist and lower amphibolite-facies conditions respectively, have been studied by combined universal-stage and electron backscatter diffraction measurements. The segments preferentially occupy orientations of ∼ 20-60 • to quartz-c and segments sub-parallel to basal and prism planes are under-represented, however, more strongly at amphibolite-facies conditions. Few segments have low-index orientations to both neighbouring grains. Coherent or nearly coherent grain boundaries represent only ∼ 2.4% of all existing grain-boundary orientations, i.e. show random distribution and, consequently, do not represent orientations of relatively low energy. At triple junctions grain-boundary segments opposite to large dihedral angles are preferentially oriented within a ∼ 25-65 • girdle to quartz-c whereas segments opposite to small dihedral angles preferentially occupy orientations partly sub-parallel to c. This suggests lower energies of segments oriented at ∼ 25-65 • to quartz-c compared to segments sub-parallel to c. Measurements on samples with different annealing temperatures show that grain-boundary segments are increasingly concentrated at ∼ 20-60 • to quartz-c with increasing temperatures. Consequently, the angle between c and grain-boundary planes represents a potential geothermometer.
A possibility for improvement of the quality of quartz crystals
Crystal Research and Technology, 1994
Experiments intended to improve the quality of seed plates for hydrothermal synthesis of quartz crystals have been performed. The plates were subjected to electro-sweeping of alkali cations. More perfect crystals were grown on such seeds. Es wurden Experimente fur die Verbesserung der Qualitit der fur die hydrothermale Synthese von Quarzkristallen bestimmten lmpflinge durchgefuhrt. Die Plattchen wurden einer Elektroextraktion der alkalischen Kationen unterworfen. Auf solchen Impflingen wurden Quarzkristalle hoher Perfektion gezuchtet.