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Hydrothermal growth and morphology of calcite single crystals
Journal of Crystal Growth 211 (2000) 458}460
Hydrothermal growth and morphology of calcite single crystals I.V. Nefyodova!,*, V.I. Lyutin!, V.L. Borodin!, P.P. Chvanski!, N.I. Leonyuk" !Russian Research Institute for the Synthesis of Minerals (VNIISIMS), Aleksandrov 601600, Vladimir District, Russia "Department of Crystallography and Crystallochemistry, Geological Faculty, Moscow State University, Moscow 119899, Russia
Abstract In this paper, an experimental study is reported for the hydrothermal growth of calcite single crystals, CaCO , using 3 the seeds parallel to pinacoid (0 0 0 1). Morphological stability of the most important faces is considered, and the real structure of these crystals was studied by X-ray topography. Physical properties of the crystals grown are similar to the rhombohedral (1 0 11 1) ones, but they have higher optical homogeneity. ( 2000 Elsevier Science B.V. All rights reserved. PACS: 81.10.Dn Keywords: Hydrothermal synthesis; Crystal growth; Morphology of crystals; Calcite
1. Introduction Single crystals of transparent natural calcium carbonate, calcite (Iceland spar), are widely used in optics due to their high birefringence and transmission in a wide range of spectrum. They are the base for manufacturing polarizers, beam divergent elements, laser shutters and other optical units. Calcite production developed in VNIISIMS (Russia) was based on the seed plates parallel to sealed rhombohedral faces (1 0 11 1) [1]. However, these rhombohedra do not "t for making large polarizers. In this case, V-shaped striations are often formed in growth pyramids [2]. As for other
* Corresponding author. Tel./fax: #7-095-939-2980. E-mail address: o"@vniisims.kc.ru (I.V. Nefyodova)
seed orientations, crystal growth becomes anomalous [3]. Nevertheless, calcite crystal growth on the pinacoidal seeds seems to be more preferable because the con"gurations of single blocks will provide the most economic machining of raw materials for optical units. For this reason, the authors of the present paper tried to develop calcite crystal growth technology on this basis, taking into account the impurity e!ects on facetting natural calcite [4]. According to Ref. [4], the natural Iceland spar is characterized by about 70 simple forms, and 20 of them are strongly developed. On the other hand, synthetic calcite grown under hydrothermal conditions has a limited number of crystal faces. The faces of M0 2 21 1N and M1 0 11 1N rhombohedra as well as M1 1 21 0N hexagonal prism are morphologically stable in the crystals obtained from the NH Br and 4 NH C1 solutions. However, the addition of 4 lithium impurity to these solutions leads to the
0022-0248/00/$ - see front matter ( 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 9 9 ) 0 0 8 0 2 - 7
I.V. Nefyodova et al. / Journal of Crystal Growth 211 (2000) 458}460
459
development of M0 0 0 1N faces, and this peculiarity was considered in this work.
2. Experimental procedure Hydrothermal solution of ammonium and halogenides having the positive factor of solubility were used for calcite crystal growth. These systems strongly attack ferrous alloys, hence experimental growth runs were carried out in `swimminga linings with the power cone shutters made of titanium alloy (Ti, Al, Zr, Sn). These cans are provided, for a pressure up to 10}20 MPa, arises as the thermal expansion of water "lled up both the bearing vessels. The value of the gauge pressure depends on the factor of "lling up the insert and autoclave. This design promotes the homogeneous temperature "elds. Thermocouples were clamped in the special pocket placed between the outer surface of liner and the internal wall of autoclave. Initial charges composed of natural calcite fractions were loaded in the lower part of an autoclave as fragments of natural crystals (dissolution zone) and the pinacoidal seed were set in an upper section (crystallization zone). These seeds were cut of natural Iceland spar crystals with an accuracy better than $30@. Saturated solutions were transferred from the lower, and the most heated zone into the higher one (more cold) owing to thermal convection. As a result of supersaturating solution in the upper section of autoclave, an excess of dissolved CaCO was deposited on the seeds. Experimental 3 conditions were as follows: temperatures of 260} 2703C, *¹"5}103C, pressures 60}80 Mpa, and a duration of 120 d. Dislocation structure of calcite crystals grown on the pinacoidal seeds was studied by X-ray topography method.
3. Results and discussion Calcite crystals obtained under the above conditions have well developed M0 0 0 1N, M0 2 21 1N and M1 0 11 1N faces (Fig. 1), as a result of the following crystal growth rates:
Fig. 1. A calcite crystal grown on the pinacoidal seeds.
Fig. 2. Microrelief of the (0 0 0 1) face in a calcite crystal grown on the pinacoidal seed.
surface containing an accessory relief and they form visually homogeneous growth sectors. Nevertheless, the surface relief consists of very small trigonal pyramids oriented to M0 0 0 1N faces at small angles (Fig. 2). As a rule, M0 2 21 1N faces have curved surfaces resulting in level-by-level growth of microscopic particles of calcite deposited on these faces in twinning positions. Morphological stability of calcite faces strongly depends on the supersaturation, temperature and concentration of hydrothermal solutions. The M1 0 11 1N, M0 2 21 1N and M0 0 0 1N faces, as F- and
460
I.V. Nefyodova et al. / Journal of Crystal Growth 211 (2000) 458}460
growth dislocations. Typical defects of crystals grown on the seeds parallel to M0 0 0 1N are zones with gas}liquid inclusions as a result of temperature instability, but in contrast to the calcite grown on the M1 0 11 1N and M1 1 21 0N oriented seeds, these crystals do not contain cracks and inhomogeneity zones.
4. Conclusions
Fig. 3. Distribution of the linear dislocations in a calcite crystal grown on the seed parallel to (0 0 0 1) face.
K-faces [5], are morphologically stable up to a supersaturation, of 1%, but a `multitopa growth appears at elevated supersaturations. Therefore, this level of supersaturation is a limiting condition for the growth of large calcite crystals with optical perfection. Further, raising supersaturation intensi"es spontaneous crystallization on the walls and "ttings of the vessel-liners. There are three types of linear dislocations distinguished by directions of their propagation. Some of the dislocations are parallel to the pinacoid growth direction, but the second and the third types of dislocations are deviated to 20}303 in one or the other sides from that direction. Most of the dislocation growth is located in the seed regeneration zone (Fig. 3). This noncoherent growth, most likely, is responsible for the formation of these
An e!ective calcite crystal growth technology under hydrothermal conditions has been developed in order to reduce the amount of waste during manufacturing of optical products and, therefore, to increase the economic e$ciency of the technological process. A number of crystal growth defects is essentially reduced in comparison with conventional technologies of calcite synthesis on the rhombohedral seeds.
References [1] V.I. Lyutin, V.V. Dronov, V.L. Borodin, V.E. Khadzhi, Proceedings of the Sixth International Conference on Crystal Growth, Moscow, 1980, Abstract, Vol. 4, pp. 169}170. [2] V.L. Lyutin, I.V. Nefyodova, Experiment Geosci. 4 (4) (1995) 77 (in Russian). [3] V.L. Borodin, V.V. Dronov, V.I. Lyutin, Syntez monocrystallicheskogo mineralnogo syrya, Moscow, 1982, pp. 21}24 (in Russian). [4] D. Dana, E. Dana, Systema Mineralogii, Inostrannaya Literatura, Moscow, 1953, Vol. 2, pp. 174}197 (in Russian). [5] M.E. Ramenskaya, Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva, 1974, Vol. 4, p. 465 (in Russian).
Hydrothermal growth and morphology of calcite single crystals I.V. Nefyodova!,*, V.I. Lyutin!, V.L. Borodin!, P.P. Chvanski!, N.I. Leonyuk" !Russian Research Institute for the Synthesis of Minerals (VNIISIMS), Aleksandrov 601600, Vladimir District, Russia "Department of Crystallography and Crystallochemistry, Geological Faculty, Moscow State University, Moscow 119899, Russia
Abstract In this paper, an experimental study is reported for the hydrothermal growth of calcite single crystals, CaCO , using 3 the seeds parallel to pinacoid (0 0 0 1). Morphological stability of the most important faces is considered, and the real structure of these crystals was studied by X-ray topography. Physical properties of the crystals grown are similar to the rhombohedral (1 0 11 1) ones, but they have higher optical homogeneity. ( 2000 Elsevier Science B.V. All rights reserved. PACS: 81.10.Dn Keywords: Hydrothermal synthesis; Crystal growth; Morphology of crystals; Calcite
1. Introduction Single crystals of transparent natural calcium carbonate, calcite (Iceland spar), are widely used in optics due to their high birefringence and transmission in a wide range of spectrum. They are the base for manufacturing polarizers, beam divergent elements, laser shutters and other optical units. Calcite production developed in VNIISIMS (Russia) was based on the seed plates parallel to sealed rhombohedral faces (1 0 11 1) [1]. However, these rhombohedra do not "t for making large polarizers. In this case, V-shaped striations are often formed in growth pyramids [2]. As for other
* Corresponding author. Tel./fax: #7-095-939-2980. E-mail address: o"@vniisims.kc.ru (I.V. Nefyodova)
seed orientations, crystal growth becomes anomalous [3]. Nevertheless, calcite crystal growth on the pinacoidal seeds seems to be more preferable because the con"gurations of single blocks will provide the most economic machining of raw materials for optical units. For this reason, the authors of the present paper tried to develop calcite crystal growth technology on this basis, taking into account the impurity e!ects on facetting natural calcite [4]. According to Ref. [4], the natural Iceland spar is characterized by about 70 simple forms, and 20 of them are strongly developed. On the other hand, synthetic calcite grown under hydrothermal conditions has a limited number of crystal faces. The faces of M0 2 21 1N and M1 0 11 1N rhombohedra as well as M1 1 21 0N hexagonal prism are morphologically stable in the crystals obtained from the NH Br and 4 NH C1 solutions. However, the addition of 4 lithium impurity to these solutions leads to the
0022-0248/00/$ - see front matter ( 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 0 2 4 8 ( 9 9 ) 0 0 8 0 2 - 7
I.V. Nefyodova et al. / Journal of Crystal Growth 211 (2000) 458}460
459
development of M0 0 0 1N faces, and this peculiarity was considered in this work.
2. Experimental procedure Hydrothermal solution of ammonium and halogenides having the positive factor of solubility were used for calcite crystal growth. These systems strongly attack ferrous alloys, hence experimental growth runs were carried out in `swimminga linings with the power cone shutters made of titanium alloy (Ti, Al, Zr, Sn). These cans are provided, for a pressure up to 10}20 MPa, arises as the thermal expansion of water "lled up both the bearing vessels. The value of the gauge pressure depends on the factor of "lling up the insert and autoclave. This design promotes the homogeneous temperature "elds. Thermocouples were clamped in the special pocket placed between the outer surface of liner and the internal wall of autoclave. Initial charges composed of natural calcite fractions were loaded in the lower part of an autoclave as fragments of natural crystals (dissolution zone) and the pinacoidal seed were set in an upper section (crystallization zone). These seeds were cut of natural Iceland spar crystals with an accuracy better than $30@. Saturated solutions were transferred from the lower, and the most heated zone into the higher one (more cold) owing to thermal convection. As a result of supersaturating solution in the upper section of autoclave, an excess of dissolved CaCO was deposited on the seeds. Experimental 3 conditions were as follows: temperatures of 260} 2703C, *¹"5}103C, pressures 60}80 Mpa, and a duration of 120 d. Dislocation structure of calcite crystals grown on the pinacoidal seeds was studied by X-ray topography method.
3. Results and discussion Calcite crystals obtained under the above conditions have well developed M0 0 0 1N, M0 2 21 1N and M1 0 11 1N faces (Fig. 1), as a result of the following crystal growth rates:
Fig. 1. A calcite crystal grown on the pinacoidal seeds.
Fig. 2. Microrelief of the (0 0 0 1) face in a calcite crystal grown on the pinacoidal seed.
surface containing an accessory relief and they form visually homogeneous growth sectors. Nevertheless, the surface relief consists of very small trigonal pyramids oriented to M0 0 0 1N faces at small angles (Fig. 2). As a rule, M0 2 21 1N faces have curved surfaces resulting in level-by-level growth of microscopic particles of calcite deposited on these faces in twinning positions. Morphological stability of calcite faces strongly depends on the supersaturation, temperature and concentration of hydrothermal solutions. The M1 0 11 1N, M0 2 21 1N and M0 0 0 1N faces, as F- and
460
I.V. Nefyodova et al. / Journal of Crystal Growth 211 (2000) 458}460
growth dislocations. Typical defects of crystals grown on the seeds parallel to M0 0 0 1N are zones with gas}liquid inclusions as a result of temperature instability, but in contrast to the calcite grown on the M1 0 11 1N and M1 1 21 0N oriented seeds, these crystals do not contain cracks and inhomogeneity zones.
4. Conclusions
Fig. 3. Distribution of the linear dislocations in a calcite crystal grown on the seed parallel to (0 0 0 1) face.
K-faces [5], are morphologically stable up to a supersaturation, of 1%, but a `multitopa growth appears at elevated supersaturations. Therefore, this level of supersaturation is a limiting condition for the growth of large calcite crystals with optical perfection. Further, raising supersaturation intensi"es spontaneous crystallization on the walls and "ttings of the vessel-liners. There are three types of linear dislocations distinguished by directions of their propagation. Some of the dislocations are parallel to the pinacoid growth direction, but the second and the third types of dislocations are deviated to 20}303 in one or the other sides from that direction. Most of the dislocation growth is located in the seed regeneration zone (Fig. 3). This noncoherent growth, most likely, is responsible for the formation of these
An e!ective calcite crystal growth technology under hydrothermal conditions has been developed in order to reduce the amount of waste during manufacturing of optical products and, therefore, to increase the economic e$ciency of the technological process. A number of crystal growth defects is essentially reduced in comparison with conventional technologies of calcite synthesis on the rhombohedral seeds.
References [1] V.I. Lyutin, V.V. Dronov, V.L. Borodin, V.E. Khadzhi, Proceedings of the Sixth International Conference on Crystal Growth, Moscow, 1980, Abstract, Vol. 4, pp. 169}170. [2] V.L. Lyutin, I.V. Nefyodova, Experiment Geosci. 4 (4) (1995) 77 (in Russian). [3] V.L. Borodin, V.V. Dronov, V.I. Lyutin, Syntez monocrystallicheskogo mineralnogo syrya, Moscow, 1982, pp. 21}24 (in Russian). [4] D. Dana, E. Dana, Systema Mineralogii, Inostrannaya Literatura, Moscow, 1953, Vol. 2, pp. 174}197 (in Russian). [5] M.E. Ramenskaya, Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva, 1974, Vol. 4, p. 465 (in Russian).