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The growth of single crystal calcite by top-seeded solution growth technique
Journal of Crystal
Growth 23 (I 974) 101-l 04 ‘0 North- Holland Publishing
THE GROWTH SOLUTION
OF SINGLE CRYSTAL CALCITE BY TOP-SEEDED
GROWTH TECHNIQUE
JOSEPH
F. BALASCIO*
Materials
Research
Pennsylvania Received
Co.
and WILLIAM
Laboratory,
B. WHITE**
The Pennsylvania
State
University,
University
Park,
16802, U.S.A.
22 February
1974
Optically clear single crystals of calcite up to 2 cm in length have been pulled from a Li,COa flux in the range of 50-75 wt”b CaCOa under a pressure of I-15 atm of carbon dioxide. The necessary phase equilibria for this growh was experimentally verified. The best growth parameters were a pull rate of 0.25 mm/hr with a rotation rate of 28 rpm. Seed orientation and perfection are critically important.
1. Introduction
2. Experimental
Calcite occurs in a wide range of natural environments, often as large single crystals, and may be as common as quartz. However, as reported in a previous communication describing a hydrothermal growth technique, attempts to produce large synthetic single crystals have not met with much success’). Certainly a varied range of growth methods have been tried. Theseincludegrowth from aqueous solutions2), gels3-5), and hydrothermal solutions’,8.9). A Czofluxes6v7), chralski growth technique is described in this paper which shows the potential for the growth of large single crystals of calcite. We will show that Li,CO,, employed as a flux, has the potential for the growth of large single crystals of calcite by the top-seeded solution growth technique (TSSG). Calcite does not readily form a melt of the same composition as the solid. For calcite to melt congruently (1339.4 “C), a carbon dioxide pressure of 1025 atm is needed”). However, a flux can be empioyed to lower to a workable range for Czochralski growth. the pco, The best flux experimentally found for this growth was lithium carbonate. This particular flux was also employed by Nestor and Schroeder6), as well as Brissot and Belin7) in their calcite growth experiments. Other binary and ternary alkali carbonate and halide flux systems proved to be unsatisfactory for the Czochralski growth of calcite’ ‘).
All Czochralski growth runs were carried out in an A.D. Little Crystal Growth Apparatus. The furnace was inductively heated, and the current to the coil was controlled by a Leeds and Northrup Series 60 C.A.T. Temperature was measured by optical pyrometer and corrected for the absorption of the sight glass. The first indication of melting of the charge was recorded on a Leeds and Northrup Azar H. Recorder. This signal originated optically from a sapphire light pipe located 1/16th of an inch from the susceptor. A 30 cm3 platinum standard-form crucible served as the susceptor. Seeds were clamped in a boron nitride holder. These seeds were cleaved from clear single crystals of Iceland spar. The seeds were oriented from backreflection Laue photographs. Prior to each run, the furnace was thoroughly cleaned and scoured. A purge cycle was employed to further eliminate the possibility of contamination from the furnace walls. Then the carbon dioxide gas was introduced and the system was slowly brought up in temperature to the first indication of melting. From here, the temperature was slowly increased until the complete charge melted. After the boule had been grown, it was kept a few millimeters above the remaining melt. Then both crucible and bottle were slowly rotated and pulled upward at approximately I mm/hr. This gradual decoupling helped to prevent thermal shock to the boule. A 1400 “C quench furnace was employed to check the phase equilibria in the Li,CO,-CaCO, system.
* Present address: Isomet Corp., 07436, U.S.A. ** Also affiliated with the Dept.
103 Bauer
Drive, Oakland,
N.J.
of Geosciences.
101
102
JOSEPH
F.
BALASCIO
Specimens were contained in platinum capsules these were quenched in carbon tetrachloride.
AND
and
3. Phase equilibria The phase diagram
for the Li,CO,-CaCO,
binary
system was published a number of years ago12). However, before it could be used as a guide for the flux pulling of calcite, data were needed at the high weight percent CaCO, end of the binary. The possibility of solid solution existed in this region. Also, there were conflicting data on the decomposition Pro2of CaCO, as a function of temperature. A series of quench runs were made at various concentrations of calcite (60 to 100 wt “/,) over the temperature interval of 600-900 “C. X-ray powder diffraction patterns were taken of the quenched products. These patterns were run at one-eighth of a degree 20 per minute against an external silicon standard. No shift in the lattice spacing of the (138) reflection of calcite was detected, implying no solid solution of Li+ in CaCO,. Therefore, the eutectic line could be extended to the pure CaCO, component (fig. 1). Data on the decomposition temperature of calcium were in good carbonate up to Pcoz= 1 atmosphere agreement ‘“,‘3P’4). However, the data were widely variant at higher pressures. A Czochralski run was made at 80 wt % CaCO,-
WILLIAM
B.
WHITE
20 wt “/ Li,CO, at 1050 f 20 “C with a Pco,in the chamber of 14 atm. At 1050 “C the surface of the melt was violently bubbling, indicating a decomposition of the carbonate in the melt. The only set of data consistent with this experiment are those of Tuttle and Harker13). Data on the decomposition of Li,CO, are even more sparse. The best data available are those reported by Kelly14). The pressure isobars plotted in fig. 1 are those co-existing with liquid, and of Kelly for Li,CO, Harker and Tuttle for CaCO, co-existing with liquid. 4. Crystal growth First a series of growth runs were made employing either a thin platinum wire or an alumina rod as a nucleator. These runs were performed with a charge of 60 wt “/, CaCO,-40 wt 9: Li,CO, at a Pcol= 10 atm. Table I is a compilation of the critical run data. In runs 5, 9, and IO, single crystal calcite was grown. The best growth was obtained in run nr.9. All runs on calcite yielded crystals with a needle habit. The needles reached 3 mm in length and were surrounded by a finegrained Li,CO,-CaCO, mixture. These experiments did prove the feasibility of nucleating and pulling calcite from a lithium carbonate flux. Next a series of runs were made by the top-seeded technique. Two seed orientations were employed: one with the crystallographic co-axis perpendicular to the melt surface and one with a rhombohedral face parallel TABLE
Tabulation
Fig. I. Phase diagram for the system LizC03-CaC03. Liquidus data from ref. 12. Eutectic extended to CaCO, composition from present experiments. CO, isobars from ref. 13.
of results
Run No.
Pull rod
Pull rate (mm/h0
I 2 3 4 5
Pt Pt Pt rt Pt
4.0 4.0 I.0
6 7 8 9
Pt Pt
IO
* C,I
I
from unseeded
pulling
Rotation (rpm)
0.25
28 2 28 2 28
AI,O, Al,03
0.25 0.25 1.0 0.25
14 2 28 28
A1203
0.25
I4
I .o
L, = Very fine-grained
mixture
of CaC03
experiments Nature bbule
of
C, t L* c,+L, C, t L GSL, C,+L,+ coarse-grained calcite c, + L, c,-L, C,LL, c, 7mL, -Icoarse-grained calcite C,mtL,A coarse-grained calcite and Li,CO,.
THE
GROWTH
OF
SINGLE
CRYSTAL
CALCITE
BY
TOP-SEEDED
to the melt surface. The composition in these runs was fixed at 65 wto/; CaCO,-35 wt% Li,CO, with Pcoz = 15 atm. A constant pull rate of 0.25 mm/hr was used. The first top-seeded growth run employed a rhombohedral seed crystal and a constant rotation of 14 rpm. The grown calcite was covered by a milky material with striations running vertically along the length of the boule (fig. 2). This feature was common to all these runs.
Fig. 2.
CaC03
bottle grown
on rhombohedral
seed faces.
SOLUTION
GROWTH
103
TECHNIQUE
Next a run was made with an (0001) seed and a rotation rate of 28 rpm. Fig. 3 shows this boule as removed from the growth apparatus. Fig. 4 shows a cross-section of the boule. A twin plane is evident which originated from the seed. Surrounding the grown central core of calcite are calcite needles. These were identified by X-ray powder diffraction. Oriented thin sections were prepared of both the central core and the polycrystalline area. The central core of the boule proved to be an oriented single crystal, while the needles were of a random orientation as evidenced by the black, gray, and light areas under crossed nicols. A section of calcite from the central core of a boule rotated at 14 rpm was highly fractured compared to the calcite grown with a rotation of 28 rpm. Fig. 4 also compared sections of calcite grown in both runs. The top section of calcite and the boule are from the 28 rpm run and the two smaller sections are from the 14 rpm run. The striations or grooves in these sections of the boule are at the interface between the polycrystalline calcite and the single crystal core. Growth perpendicular to the c-axis was rather limited due to the formation of the polycrystalline material. TABLE 2 Spcctrochemical analyses grade calcite Element
Fig. 3.
CaC03
boule
grown
on c-oriented
seed.
Fig. 4. Transverse and longitudinal cross-sections under crossed Nichols. Top longitudinal section and transverse section from boule grown with 28 rpm stirring: bottom two longitudinal sections from boule grown with I4 rpm stirring.
Li Na K Rb Sr Mn Fe cu
Iceland spar
of TSSG, natural (all data in ppm) Starting material
and reagent
Outside needles 100-150
I O-50 200 100~200
Crystal core 150-200
700 5520 IO-20
-
2550 50-70
25-50 25-40
200 -
Although single crystal calcite can be grown by topseeded flux pulling, the technique is very dependent on orientation and perfection of seeds. Because of the slow growth rate in all directions not parallel to the optic axis, the crystals cannot be necked down. Instead the seed is propagated as a bar of oriented single crystal. Large (0001) seed plates would therefore be necesssary for the growth of large crystals. The results of chemical analysis are shown m table 2. There is a small uptake of lithium from the flux, but the impurities in the CaCO, reagent have been re-
JOSEPH
104
F.
BALASCIO
jetted. All the impurities in the boule appear to be due to the impurities present in the Li,C03. No appreciable difference is found between the purity of the needles and the calcite core of the boule. Acknowledgments This work was supported by the Advanced Projects Agency under Contract DA-49-083.
Research
References I) J. F. Balascio
and W. B. White,
Mater.
Res. Bull. 7 (1972)
1461. 2) P. M. Gruzensky,
in: Cr.rstrr/ Growth, Ed. H. S. Peiser (Pergamon, Oxford, 1967) p. 365. 3) J. W. McCauley, M. S. Thesis (Mineralogy), The Pennsylvania State Univ. (June, 1965).
AND
WILLIAM
B.
WHITE
4) H. J. Nick1 and H. K. Henisch, J. Electrochem. Sot. 116 (1969) 1252. 5) A. Schwartz, D. Eckart, J. O’Connell and K. Francis, Mater. Res. Bull. 6 (1971) 1341. 6) J. F. Nestor and J. B. Schroeder, Am. Mineralogist 52 (I 967) 276. 7) J. J. Brissot and C. Belin, J. Cryst. Growth 8 (1971) 213. 8) N. Yu. Ikornikova, in: Hydrotharmnl Synthesis oJ‘ Crystcrls. Ed. A. N. Lobachev (Consultants Bureau, New York, 1971). 9) V. G. Hill and R. I. Harker, Air Force Materials Laboratory Tech. Report AFML-TR-67-51 I (1967) 46. IO) F. H. Smyth and L. H. Adams, J. Am. Chem. Sot. 45 (1923) 1167. I I) J. F. Balascio, Ph. D. Dissertation, The Pennsylvania State Univ. (1972). 12) V. W. Eitel and W. Skaliks, Z. Anorg. Allgem. Chem. 183 (1929) 263. 13) R. 1. Harker and 0. F. Tuttle, Am. J. Sci. 13 (1955) I. 14) K. K. Kelly, Bureau of Mines, Bull. 384 (1962) I.
Growth 23 (I 974) 101-l 04 ‘0 North- Holland Publishing
THE GROWTH SOLUTION
OF SINGLE CRYSTAL CALCITE BY TOP-SEEDED
GROWTH TECHNIQUE
JOSEPH
F. BALASCIO*
Materials
Research
Pennsylvania Received
Co.
and WILLIAM
Laboratory,
B. WHITE**
The Pennsylvania
State
University,
University
Park,
16802, U.S.A.
22 February
1974
Optically clear single crystals of calcite up to 2 cm in length have been pulled from a Li,COa flux in the range of 50-75 wt”b CaCOa under a pressure of I-15 atm of carbon dioxide. The necessary phase equilibria for this growh was experimentally verified. The best growth parameters were a pull rate of 0.25 mm/hr with a rotation rate of 28 rpm. Seed orientation and perfection are critically important.
1. Introduction
2. Experimental
Calcite occurs in a wide range of natural environments, often as large single crystals, and may be as common as quartz. However, as reported in a previous communication describing a hydrothermal growth technique, attempts to produce large synthetic single crystals have not met with much success’). Certainly a varied range of growth methods have been tried. Theseincludegrowth from aqueous solutions2), gels3-5), and hydrothermal solutions’,8.9). A Czofluxes6v7), chralski growth technique is described in this paper which shows the potential for the growth of large single crystals of calcite. We will show that Li,CO,, employed as a flux, has the potential for the growth of large single crystals of calcite by the top-seeded solution growth technique (TSSG). Calcite does not readily form a melt of the same composition as the solid. For calcite to melt congruently (1339.4 “C), a carbon dioxide pressure of 1025 atm is needed”). However, a flux can be empioyed to lower to a workable range for Czochralski growth. the pco, The best flux experimentally found for this growth was lithium carbonate. This particular flux was also employed by Nestor and Schroeder6), as well as Brissot and Belin7) in their calcite growth experiments. Other binary and ternary alkali carbonate and halide flux systems proved to be unsatisfactory for the Czochralski growth of calcite’ ‘).
All Czochralski growth runs were carried out in an A.D. Little Crystal Growth Apparatus. The furnace was inductively heated, and the current to the coil was controlled by a Leeds and Northrup Series 60 C.A.T. Temperature was measured by optical pyrometer and corrected for the absorption of the sight glass. The first indication of melting of the charge was recorded on a Leeds and Northrup Azar H. Recorder. This signal originated optically from a sapphire light pipe located 1/16th of an inch from the susceptor. A 30 cm3 platinum standard-form crucible served as the susceptor. Seeds were clamped in a boron nitride holder. These seeds were cleaved from clear single crystals of Iceland spar. The seeds were oriented from backreflection Laue photographs. Prior to each run, the furnace was thoroughly cleaned and scoured. A purge cycle was employed to further eliminate the possibility of contamination from the furnace walls. Then the carbon dioxide gas was introduced and the system was slowly brought up in temperature to the first indication of melting. From here, the temperature was slowly increased until the complete charge melted. After the boule had been grown, it was kept a few millimeters above the remaining melt. Then both crucible and bottle were slowly rotated and pulled upward at approximately I mm/hr. This gradual decoupling helped to prevent thermal shock to the boule. A 1400 “C quench furnace was employed to check the phase equilibria in the Li,CO,-CaCO, system.
* Present address: Isomet Corp., 07436, U.S.A. ** Also affiliated with the Dept.
103 Bauer
Drive, Oakland,
N.J.
of Geosciences.
101
102
JOSEPH
F.
BALASCIO
Specimens were contained in platinum capsules these were quenched in carbon tetrachloride.
AND
and
3. Phase equilibria The phase diagram
for the Li,CO,-CaCO,
binary
system was published a number of years ago12). However, before it could be used as a guide for the flux pulling of calcite, data were needed at the high weight percent CaCO, end of the binary. The possibility of solid solution existed in this region. Also, there were conflicting data on the decomposition Pro2of CaCO, as a function of temperature. A series of quench runs were made at various concentrations of calcite (60 to 100 wt “/,) over the temperature interval of 600-900 “C. X-ray powder diffraction patterns were taken of the quenched products. These patterns were run at one-eighth of a degree 20 per minute against an external silicon standard. No shift in the lattice spacing of the (138) reflection of calcite was detected, implying no solid solution of Li+ in CaCO,. Therefore, the eutectic line could be extended to the pure CaCO, component (fig. 1). Data on the decomposition temperature of calcium were in good carbonate up to Pcoz= 1 atmosphere agreement ‘“,‘3P’4). However, the data were widely variant at higher pressures. A Czochralski run was made at 80 wt % CaCO,-
WILLIAM
B.
WHITE
20 wt “/ Li,CO, at 1050 f 20 “C with a Pco,in the chamber of 14 atm. At 1050 “C the surface of the melt was violently bubbling, indicating a decomposition of the carbonate in the melt. The only set of data consistent with this experiment are those of Tuttle and Harker13). Data on the decomposition of Li,CO, are even more sparse. The best data available are those reported by Kelly14). The pressure isobars plotted in fig. 1 are those co-existing with liquid, and of Kelly for Li,CO, Harker and Tuttle for CaCO, co-existing with liquid. 4. Crystal growth First a series of growth runs were made employing either a thin platinum wire or an alumina rod as a nucleator. These runs were performed with a charge of 60 wt “/, CaCO,-40 wt 9: Li,CO, at a Pcol= 10 atm. Table I is a compilation of the critical run data. In runs 5, 9, and IO, single crystal calcite was grown. The best growth was obtained in run nr.9. All runs on calcite yielded crystals with a needle habit. The needles reached 3 mm in length and were surrounded by a finegrained Li,CO,-CaCO, mixture. These experiments did prove the feasibility of nucleating and pulling calcite from a lithium carbonate flux. Next a series of runs were made by the top-seeded technique. Two seed orientations were employed: one with the crystallographic co-axis perpendicular to the melt surface and one with a rhombohedral face parallel TABLE
Tabulation
Fig. I. Phase diagram for the system LizC03-CaC03. Liquidus data from ref. 12. Eutectic extended to CaCO, composition from present experiments. CO, isobars from ref. 13.
of results
Run No.
Pull rod
Pull rate (mm/h0
I 2 3 4 5
Pt Pt Pt rt Pt
4.0 4.0 I.0
6 7 8 9
Pt Pt
IO
* C,I
I
from unseeded
pulling
Rotation (rpm)
0.25
28 2 28 2 28
AI,O, Al,03
0.25 0.25 1.0 0.25
14 2 28 28
A1203
0.25
I4
I .o
L, = Very fine-grained
mixture
of CaC03
experiments Nature bbule
of
C, t L* c,+L, C, t L GSL, C,+L,+ coarse-grained calcite c, + L, c,-L, C,LL, c, 7mL, -Icoarse-grained calcite C,mtL,A coarse-grained calcite and Li,CO,.
THE
GROWTH
OF
SINGLE
CRYSTAL
CALCITE
BY
TOP-SEEDED
to the melt surface. The composition in these runs was fixed at 65 wto/; CaCO,-35 wt% Li,CO, with Pcoz = 15 atm. A constant pull rate of 0.25 mm/hr was used. The first top-seeded growth run employed a rhombohedral seed crystal and a constant rotation of 14 rpm. The grown calcite was covered by a milky material with striations running vertically along the length of the boule (fig. 2). This feature was common to all these runs.
Fig. 2.
CaC03
bottle grown
on rhombohedral
seed faces.
SOLUTION
GROWTH
103
TECHNIQUE
Next a run was made with an (0001) seed and a rotation rate of 28 rpm. Fig. 3 shows this boule as removed from the growth apparatus. Fig. 4 shows a cross-section of the boule. A twin plane is evident which originated from the seed. Surrounding the grown central core of calcite are calcite needles. These were identified by X-ray powder diffraction. Oriented thin sections were prepared of both the central core and the polycrystalline area. The central core of the boule proved to be an oriented single crystal, while the needles were of a random orientation as evidenced by the black, gray, and light areas under crossed nicols. A section of calcite from the central core of a boule rotated at 14 rpm was highly fractured compared to the calcite grown with a rotation of 28 rpm. Fig. 4 also compared sections of calcite grown in both runs. The top section of calcite and the boule are from the 28 rpm run and the two smaller sections are from the 14 rpm run. The striations or grooves in these sections of the boule are at the interface between the polycrystalline calcite and the single crystal core. Growth perpendicular to the c-axis was rather limited due to the formation of the polycrystalline material. TABLE 2 Spcctrochemical analyses grade calcite Element
Fig. 3.
CaC03
boule
grown
on c-oriented
seed.
Fig. 4. Transverse and longitudinal cross-sections under crossed Nichols. Top longitudinal section and transverse section from boule grown with 28 rpm stirring: bottom two longitudinal sections from boule grown with I4 rpm stirring.
Li Na K Rb Sr Mn Fe cu
Iceland spar
of TSSG, natural (all data in ppm) Starting material
and reagent
Outside needles 100-150
I O-50 200 100~200
Crystal core 150-200
700 5520 IO-20
-
2550 50-70
25-50 25-40
200 -
Although single crystal calcite can be grown by topseeded flux pulling, the technique is very dependent on orientation and perfection of seeds. Because of the slow growth rate in all directions not parallel to the optic axis, the crystals cannot be necked down. Instead the seed is propagated as a bar of oriented single crystal. Large (0001) seed plates would therefore be necesssary for the growth of large crystals. The results of chemical analysis are shown m table 2. There is a small uptake of lithium from the flux, but the impurities in the CaCO, reagent have been re-
JOSEPH
104
F.
BALASCIO
jetted. All the impurities in the boule appear to be due to the impurities present in the Li,C03. No appreciable difference is found between the purity of the needles and the calcite core of the boule. Acknowledgments This work was supported by the Advanced Projects Agency under Contract DA-49-083.
Research
References I) J. F. Balascio
and W. B. White,
Mater.
Res. Bull. 7 (1972)
1461. 2) P. M. Gruzensky,
in: Cr.rstrr/ Growth, Ed. H. S. Peiser (Pergamon, Oxford, 1967) p. 365. 3) J. W. McCauley, M. S. Thesis (Mineralogy), The Pennsylvania State Univ. (June, 1965).
AND
WILLIAM
B.
WHITE
4) H. J. Nick1 and H. K. Henisch, J. Electrochem. Sot. 116 (1969) 1252. 5) A. Schwartz, D. Eckart, J. O’Connell and K. Francis, Mater. Res. Bull. 6 (1971) 1341. 6) J. F. Nestor and J. B. Schroeder, Am. Mineralogist 52 (I 967) 276. 7) J. J. Brissot and C. Belin, J. Cryst. Growth 8 (1971) 213. 8) N. Yu. Ikornikova, in: Hydrotharmnl Synthesis oJ‘ Crystcrls. Ed. A. N. Lobachev (Consultants Bureau, New York, 1971). 9) V. G. Hill and R. I. Harker, Air Force Materials Laboratory Tech. Report AFML-TR-67-51 I (1967) 46. IO) F. H. Smyth and L. H. Adams, J. Am. Chem. Sot. 45 (1923) 1167. I I) J. F. Balascio, Ph. D. Dissertation, The Pennsylvania State Univ. (1972). 12) V. W. Eitel and W. Skaliks, Z. Anorg. Allgem. Chem. 183 (1929) 263. 13) R. 1. Harker and 0. F. Tuttle, Am. J. Sci. 13 (1955) I. 14) K. K. Kelly, Bureau of Mines, Bull. 384 (1962) I.