Natural Quartz Crystals Research Articles

Distribution of OH in synthetic and natural quartz crystals

The relative intensities of different OH vibration bands have been studied in synthetic quartz crystals with total OH concentration varying by more than a factor of 30 by means of infrared absorption measurements at 78°K. Local variations of OH concentration also have been measured for different directions in these samples and in two crystals of natural quartz from Brazil. Integral absorptions of the different bands in the 3400 cm −1 region were all found to increase linearly with total OH concentration. Therefore, mechanical Q could be related to any one band of the spectrum as well as to the total OH concentration. Since for natural quartz no relation between total OH concentration and mechanical Q seems to exist, the effect of OH defects characteristic for synthetic quartz must be high, while the OH defects characteristic for natural quartz (i.e., rock crystals and smoky quartz) have a small effect on the mechanical Q. OH concentrations in the Z- and + X-zones were found to be lower near the edge than near the seed. The concentration of OH varies in the order Z < + X ⪡ − X, suggesting that OH acts as a charge compensator for metal impurities, notably Al +3. In natural quartz, the OH concentrations near the edge were also lower than in the interior parts. The overall differences for different directions were much smaller than in the case of synthetic quartz.

Distributions of OH in synthetic and natural quartz crystals: Dipak Chakraborty, Central Glass and Ceramic Research Institute, Jadavpur, Cal-700032, West Bengal, India, and Gerhard Lehmann, Institut für Physikalische Chemie der Universität Münster, 44 Münster, West Germany

Distributions of OH in synthetic and natural quartz crystals: Dipak Chakraborty, Central Glass and Ceramic Research Institute, Jadavpur, Cal-700032, West Bengal, India, and Gerhard Lehmann, Institut für Physikalische Chemie der Universität Münster, 44 Münster, West Germany

Anisotropy in the track development properties of various crystallographic planes of natural quartz crystals

Abstract Fission fragment track development properties of x-cut (1, 0, 0), y-cut (0, 1, 0) and z-cut (0, 0, 1) planes in natural quartz crystals have been studied. Both HF and boiling solution of NaOH have been used as etchants. It has been found that x-cut and y-cut planes show quite significant anisotropy in the angular distribution of etched tracks. The degree of isotropy is higher when boiling solution of NaOH is used as an etchant than HF etching. Among the planes studied, the x-cut plane is found to be the most sensitive, while no etchable tracks could be obtained in z-cut plane. In the early stages of the etching process, the degree of isotropy seems to increase with the increasing etching time. Attempts have been made to explain these observations.

Natural quartz: A useful detector for in-core measurements

Experiments have been carried out to study the track registration and retention properties of natural quartz crystals. The results indicate that important characteristics such as the critical angle of etching ( θ c ), the etchable track formation efficiency (η), the maximum etched track length ( l max) and the track stability against high temperature annealing depend upon the particular crystallographic plane. It has also been observed that a natural quartz crystal is more efficient than fuzed silica (Vitreosil) for the registration and retention of fission fragment latent damage trails at elevated temperatures. Preliminary results indicate that gamma doses below ∼200 Mr do not affect the above-mentioned properties of these crystals. The experiments seem to suggest that a natural quartz crystal is probably the only known insulating solid in which the fission tracks are fairly stable, (a) at temperatures as high as ∼800 °C (maintained for a few hours), and (b) under fairly severe background conditions. It may therefore prove to be an extremely useful track detector for measurements in high temperature and radiation environments such as reactor cores.

Plastic-deformati on mechanisms in quartz: The effect of water

High-temperature and pressure-deformation experiments indicate that small amounts of water strongly affect the plastic-deformation mechanisms that operate in quartz. Inherently dry natural quartz crystals exhibit a transition from T = (0001), t = 〈11 2 ̄ 0〉 to T = {10 1 ̄ 0} , t = [0001] glide at approximately 700° C at a strain rate of 8 · 10 −6 sec −1 . The transition temperature decreases with decreasing strain rate. When water is diffused into dry natural crystals at high temperature, duplex slip occurs on the systems (0001), 〈112&#x0304;0〉and either {112&#x0304;0}, [0001] or {101&#x0304;0}, [0001] depending on which of the latter systems is most highly stressed. Hydrothermally grown synthetic quartz crystals contain relatively large amounts of structurally bound water. In these crystals, a transition occurs from (0001), 〈112&#x0304;0〉 to dominantly pencil glide in the [0001] and possibly 〈112&#x0304;3〉 directions. The transition temperature is strongly dependent on the water content of the crystals, and coincides with the hydrolytic weakening temperature defined by Griggs and Blacic for these crystals. Inhomogeneous distribution of water in the synthetic crystals controls the distribution of plastic strain and may, in part, control the orientation of subbasal deformation lamellae in these. It is suggested that anisotropic diffusion of H-OH in quartz may be responsible for the operation of the [0001] pencil-glide system in the hydrolytic weakening regime. Crystal structure anisotropy may also play a role in the slip-system transition through its influence on the Peierls stress, and this is most likely the dominant factor in the dry crystals.

Transient changes in quartz resonators following exposure to pulse ionization

Abstract This paper is a review of the transient effect of pulse ionization on the resonant frequency and Q of quartz resonators. A number of different samples of both natural and synthetic quartz crystals have been used. Fifth-overtone 5, 32, and 125 MHz thickness shear (AT-cut) crystal units were fabricated and studied using several different oscillator circuits, one of which was designed such that the resistance Rs (αQ −1) of the crystal unit at series resonance as well as frequency could be measured after pulse exposure. With the exception of one purposely altered crystal, all the resonators exhibited a negative-transient frequency offset after irradiation which thereafter anneals as a function of t −1/2 over nearly four decades of time. The pulse irradiation effect on Q −1 is most striking at 5 MHz in natural quartz units, which suffer a thirty-fold increase in acoustic absorption after exposure to 104 rad. The transient increase in the acoustic absorption in natural quartz anneals within 10 seconds ...

Transport properties of MoTe 2− x and MoSe 2− x compounds between 130 and 300° K : A. Conan, G. Goureaux and M. Zoaeter, Laboratoire de Physique du Métal, Institut de Physique de l'Université de Nantes, 44037. Nantes-Cedex, France

It has been shown that the near infrared bands present at 3306, 3367, 3520 and 3507 cm−1 in natural quartz crystals can get transferred to cultured quartz if the hydrothermal synthesis is carried out at high pressures. These bands upon a chosen sequence of 77 K and 300 K-irradiations in both natural as well as cultured quartz synthesized at high pressures showed a similar radiation response pattern. This suggests that these bands represent similar species of hydroxyl point defects in the two types of quartz, natural and cultured.

Stratigraphical etch patterns on the rhombohedral cleavages of natural quartz crystals

Summary Rhombohedral cleavage faces of quartz have been etched hydrothermally and with fused KOH. Stratigraphical etch patterns were observed on isolated cleavages, matched cleavage faces, and opposite sides of a thin flake. The angle between the () cleavage plane and the planes responsible for the stratigraphical patterns was almost equal to the interfacial angle, 46° 16′ between adjacent rhombohedral faces. It is concluded that the stratigraphical patterns formed by preferential etching reveal the edges of weak planes deposited during growth. The implications are discussed.

Influence of Hydrogen and Alkali Impurities on the High‐Temperature Indentation Hardness of Natural Quartz Crystals

The indentation hardness of a natural quartz crystal was measured from 25° to 1000°C. The concentrations of alkali ions and hydrogen were varied by annealing and electrolysis; hydrogen content was determined from infrared absorption. The untreated crystal was soft from 500° to 850°C; there was evidence of transformation beneath the indenter to a phase of silica denser than quartz. When the crystal was annealed to remove alkali ions and hydrogen, it remained hard throughout the temperature range of the tests. Injection of hydrogen by electrolysis into previously annealed specimens reduced the strength slightly; injection of lithium by electrolysis produced a greater reduction in hardness. Only the untreated samples and those doped with lithium appeared to have transformed to a denser phase. Thus, trace impurities can influence the hardness of quartz by acting as “mineralizers” to promote densification and by facilitating normal deformation mechanisms involving dislocations.

Velocities of First and Zero Sound in Quartz

The temperature dependence of the velocity of sound in $X$-cut and $\mathrm{BC}$-cut natural quartz crystals has been measured in the range 4 to 75 \ifmmode^\circ\else\textdegree\fi{}K. Measurements were made at frequencies of 35, 100, and 1000 MHz. By assuming that at these frequencies the velocity is frequency independent at 4 \ifmmode^\circ\else\textdegree\fi{}K, these results can be used to obtain the frequency dependence of the velocity at higher temperatures. At temperatures below 20 \ifmmode^\circ\else\textdegree\fi{}K, or above about 65 \ifmmode^\circ\else\textdegree\fi{}K, there is no velocity dispersion in the frequency range studied, to within the experimental uncertainty. In the temperature range between 20 and about 65 \ifmmode^\circ\else\textdegree\fi{}K, the velocity is greater at 1000 MHz than at the lower frequencies, both for the $X$-cut and the $\mathrm{BC}$-cut crystals. These results are compared with theories of velocity dispersion due to interaction with thermal phonons, and qualitative agreement is obtained.

Sources and spectra of the thermoluminescence for natural quartz crystals

Sources and spectra of the thermoluminescence for natural quartz crystals

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

AbstractTransmission electron microscopy has 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 (0001). In 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 the higher temperature there are dislocations in the twin bands and other regions of the crystals with dislocations 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.

Dislocations in Quartz Observed by Transmission Electron Microscopy

Arrays and networks of dislocations have been observed by diffraction contrast electron microscopy in crystals of natural milky quartz. These arrays and networks have been analyzed in terms of Burgers vectors suggested from examination of the crystal structure. The relevance of these dislocations to the plastic deformation of quartz is discussed.

Elastic strain and coloration pattern in natural quartz crystals

Very small elastic strains (tilts of the order of 0.25 sec of arc and dilationsΔd/d≃10−6, whered is the spacing of net planes) have been observed in natural quartz crystals. According to their rocking curves which are of almost theoretical width, these crystals were commonly expected to be practically perfect crystals. On double crystal X-ray topographs a pattern was revealed of uniformly strained layers parallel to the rhombohedron faces (10¯11) and with thickness ranging between 20 and 200 microns. This fine structure strain pattern was correlated to the pattern of the optical coloration which could be produced by irradiating the originally transparent crystals with X-rays. A localincrease of coloration matched with a localcontraction of the lattice. Tilts occurred in transition zones between adjacent layers with slightly different lattice spacings. Strain and coloration patterns probably have as a common cause the deposition of layers with different impurity concentrations during the growth process of the crystals. Although no change of the strain as a result of the X irradiation could be detected in the colored layers in particular, experimental evidence has been found for anoverall expansion of the lattice of the order ofΔd/d≃5×10−7 due to X irradiation. This expansion seems to saturate at this low value and is probably caused by electronic processes connected with the coloration. Some aspects concerning the nature of the color centers have been discussed. It seems likely from the results of the strain measurements that both sets of layers, colored and transparent ones, play a combined role in coloration.

Rare findings of prism faces of natural quartz

Several hundreds of natural quartz crystals obtained from overseas mines and from the Pannala Hills, Amreli District (Gujarat State, India) have been examined under a metallurgical phase contrast microscope. First evidence of screw dislocations and spirals on prism faces of natural quartz crystals are reported. The slip step observed on the prism face is shown to be parallel to the trace of a major rhombohedral plane, which is a direction of the ‘partial cleavage’. The increasing straight slope of the slip step emerging from the face has been attributed to the screw dislocation. Rectangular and irregular spirals are illustrated and interpreted as growth spirals.

Relation Between E′ Centers and Hydroxyl Bonds in Silica

The relation between the concentration of intrinsic paramagnetic states (the E′ centers) of silica (silica glass) produced by irradiation and the concentration of OH− ions in the silica was investigated by introducing OH− ions into silica, initially free of these ions, in a controlled manner. Optical absorption and electron spin resonance measurements were used to establish the relation. The results of the investigation showed that in synthetic silicas the concentration of E′ centers varied linearly with the concentration of hydroxyl units, the sum of the concentrations of hydroxyl units and E′ centers being constant. A ``vacancy'' model for the silica structure is proposed. In terms of this model the estimated saturation concentration of E′ centers is of the same order as the concentration of ``vacancies,'' ∼1020 cm−3. The saturation concentration of hydroxyl units is also ∼1020 cm−3. Silica made by fusing natural quartz crystals differs from the synthetic silica with respect to the optical bands and the electron spin resonance spectra produced by irradiation. The effects of introducing hydroxyl units into natural quartz silica initially free of hydroxyl units is also different. These differences between natural quartz silica and synthetic silica are related to the models which have been suggested for the E′ centers. The models which are suggested are in agreement with the results of other experiments.

Mechanical Resonance Dispersion and Plastic Flow in Crystalline Solids

An explanation is given for the mechanical resonance dispersions observed at audio-frequencies in many crystalline solids. The resonances are considered to result from alternating simultaneous slip occurring on transient slip planes with mean lifetimes of 10−2 to 10−4 sec. The slip along such planes is opposed by displacement-dependent, velocity dependent, and acceleration-dependent stresses. These last two stresses are found to be of magnitudes which can result from the interchange of atoms across a slip plane with a consequent decrease of momentum of the fast moving (slipped) part of the sample undergoing deformation. If the rate of transfer is independent of the slip process, a velocity-dependent (viscous) stress results, but if some of the atoms are induced to transfer as a direct result of the slip itself, then an acceleration-dependent stress is present. These slip planes, because of their sudden formation, short lifetimes, and inertial coefficients, do not contribute to the static or ultrasonic compliance, but do affect the dynamic compliance at audio frequencies. The transient slip planes are supposed to be generated by the movement of dislocations across the sample. Thus, a concept of combined consecutive and simultaneous slip is suggested in which dislocations remain an essential part of the mechanism but are not the sole source of deformation. An interesting consequence of the theory is that a critical stress for plastic flow or, alternatively, for brittle fracture can be predicted from values of the dynamic compliance (or modulus). Predicted values of critical stress (for both single crystals and polycrystalline metals) made from the dynamic modulus at 100 cps are much closer to the observed values than those made on the basis of either the static or ultrasonic moduli. In particular, it is found that the predicted values for brittle fracture stress agree almost exactly with observed breaking stresses for single crystals of sodium chloride, germanium, glycine sulfate, and, at two temperatures and orientations, for natural quartz crystals. The occurrence of negative absorption or induced emission is discussed, and a means of generating sustained, self-excited, audio-frequency oscillations in a crystalline solid is outlined. The possibility of mechanical failure at an intrinsic material resonance is considered briefly and some other aspects of the mechanical behavior of crystalline solids are also examined.

Excitation, Detection, and Applications of Hypersonic Waves

A new method for the generation and detection of ultra high-frequency sound waves has been recently described [H. E. Bömmel and K. Dransfeld, Phys. Rev. Letters 1, 234 (1958)]. It is based on piezoelectric surface excitation at the ends of a quartz rod placed between two identical microwave cavities. Longitudinal as well as transverse waves have been generated this way and have been transmitted into other media by means of compressional bond techniques. This method together with the simultaneously discovered fact that the attenuation of hypersonic waves in quartz is very small at temperatures below 15°K should make it now possible to extend ultrasonic research up to frequencies of about 1011 cps. It should allow to investigate problems in solid state and liquid state physics involving phonon-phonon interactions, the interactions of phonons with spins, electrons, rotons, etc., at frequencies approaching those of the thermal phonons at low temperatures. Surface excitation should not be restricted to piezoelectric materials but should also be applicable to magnetostrictive substances as for example in ferromagnetic resonance. The results of hypersonic absorption measurements as a function of temperature in natural, synthetic, and neutron irradiated quartz crystals in the frequency range between 1000 and 4000 mc/sec will be presented.

Asymmetric X-ray reflexion from natural quartz crystals

Asymmetric X-ray reflexion from natural quartz crystals

A study of color centers produced in quartz by x-radiation.

Z-cut sections of natural quartz crystals were colored to saturation by x-irradiation from a beryllium window x-ray tube. The crystal sections were decolored by heating and recolored by further x-radiation. The same optical transmissions, at saturation, were obtained when the energy distribution of the x-ray beam was the same but were different when different voltages were applied to the x-ray tube. The heat treatment used in removing the color from quartz does not affect the value of the optical transmission when recolored by x-radiation to saturation. It was observed that in every case the rate of coloration was greater after the section had been cleared and re-irradiated than when the color was being produced for the first time. If the heat treatment is restricted to an amount barely sufficient to remove the coloration, then the rate follows the same curve on successive irradiation cycles. If the crystal section is baked for a longer period of time than that stated above, the rate decreases and approaches that of fresh quartz. The change in rate of coloration of quartz is governed by the immediately preceding heat treatment employed in removing the color centers. No “memory” of previous heat treatments appears to be present.