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Growth habits and characterization of Sr3NbGa3Si2O14 crystal
ARTICLE IN PRESS
Journal of Crystal Growth 292 (2006) 404–407 www.elsevier.com/locate/jcrysgro
Growth habits and characterization of Sr3NbGa3Si2O14 crystal Jianjun Chen, Erwei Shi, Yanqing Zheng, Haikuan Kong, Hui Chen Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, PR China Available online 9 June 2006
Abstract Ordered piezoelectric Sr3NbGa3Si2O14 (SNGS) single crystal with langasite family structure has been successfully grown with clear facet using Czochralski technique. The growth habit of SNGS crystal is revealed and discussed in detail. It is shown that the crystal is easily grown along /1 0 0S direction, and {1 0 0}, {0 0 1} plus {3 0 2} faces are strongly exposed as facets. Detailed X-ray powder diffraction (XRPD) patterns and indices calculated and observed for the crystal are given. The lattice parameters calculated from the ˚ c ¼ 5:07998 0:000481 A, ˚ V ¼ 301:8 A˚ 3 and the density is 4.6456 kg/m3. The density XRPD data are a ¼ 8:28626 0:000911 A, measured for SNGS crystal by Archimedes method is 4.6834 kg/m3. Etching experiments have been performed on {1 1 0}, {0 1 0} and {0 0 1} faces to observe the etch patterns. The transmittance spectra from 200 to 3000 nm have been measured and the absorption edge is determined to be 268 nm. r 2006 Elsevier B.V. All rights reserved. PACS: 81.10; 61.66.F; 81.70.P; 78.20; 81.05; 82.80 Keywords: A1. Crystal structure; A1. Facet; A1. X-ray diffraction; A2. Czochralski method; B1. Gallium compounds; B2. Piezoelectric materials
1. Introduction From 1980s to now, langasite family (including La3Ga5SiO14, Sr3Ga2Ge4O14, La3Nd0.5Ga5.5O14 and La3Ta0.5Ga5.5O14) with A3BC3D2O14 structure has attracted much attention for their excellent properties in applications of surface acoustic wave, bulk acoustic wave and sensors fields [1–7]. As the further development of research on LGS (La3Ga5SiO14), LGN (La3Nd0.5Ga5.5O14), LGT (La3Ta0.5Ga5.5O14) and SGG (Sr3Ga2Ge4O14), several disadvantage of these materials have been perceived [8]. First, the crystal structure of these compounds is ‘‘disordered.’’ The ‘‘disordered’’ structure results primarily from the fact that two of the different cations in each compound randomly share the same sites in the unit cell. A ‘‘disordered’’ structure causes randomly distributed distortion of the crystal structure, which is affecting the crystal uniformity and reproducibility and leading to the lower than ideally achievable acoustic Q and electromechanical coupling. Second, it is known that LGS, LGN, LGT and SGG melt congruently, but the exact Corresponding author. Tel.: +86 21 69987761; fax: +86 21 59927184.
E-mail addresses: [email protected], [email protected] (J. Chen). 0022-0248/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2006.04.044
phase diagrams have not been reported. The congruent melt points are not located on their stoichiometric composition. Third, for LGS, LGN and LGT, high content of Ga2O3 in these materials makes the crystals cost much higher than aquartz, LiTaO3 and LiNbO3. As with SGG, though the content of Ga2O3 decreases, high content of GeO2 makes the crystal growth much more difficult due to the strong evaporation of GeO2 [6]. Based on the understanding of ‘‘disordered’’ structure, compounds have been found four completely ‘‘ordered’’ langasite structure [9]. They are Sr3NbGa3Si2O14 or SNGS, Sr3TaGa3Si2O14 or STGS, Ca3NbGa3Si2O14 or CNGS and Ca3TaGa3Si2O14 or CTGS. Up to now, there are few reports concerning the growth and properties of ordered single crystals [8,10–14]. In this work, we demonstrate the successful growth of SNGS and reveal the growth habits. Also, the optical properties of the crystal have been measured. 2. Experimental procedure The starting materials used for crystal growth were prepared from a through mixture of 99.99% SrCO3,
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Nb2O5, Ga2O3 and SiO2 powders at stoichiometric composition. The compounds were pressed into blocks and sintered at a temperature of 1300 1C in an atmosphere of air for 24 h to synthesize polycrystalline SNGS through solid state reaction. X-ray powder diffraction (XRPD) data of synthesized material and different parts of the single crystal were collected at room temperature on a Rigaku D/ Max-2550V diffractometer from 101 to 701 (2y) with Cu Ka ˚ Upon identification radiation of wavelength l ¼ 1:5418 A. of the single phase LGS structure by XRPD analysis, the synthesized specimens were charged into the crucible for crystal growth. Single crystal growth was carried out by a conventional induction-heating CZ furnace with an iridium crucible (65 mm in diameter and 45 mm height). An after-heater system made of platinum was installed. The growth atmosphere was a mixture of N2 and 1 vol% O2 gas in order to restrain the evaporation of gallium oxide from the melt during crystal growth. The SNGS single crystal growth runs were performed respectively along /0 0 1S and /1 0 0S directions with LGS seeds. The pulling rate was 1–3 mm/h while the crystal rotation rate was 15–25 rpm. Before crystal growth, the melt of starting materials was maintained about 50 1C above the melting temperature for several hours in order to homogenize the melt. After the growth, the crystal was cooled to room temperature at a rate of 70 1C/h. After the growth, the crystals were identified from top to bottom by XRPD analysis. The crystal’s growth habits were discussed and the lattice parameters and the density of the crystal were calculated from the data of XRPD. Archimedes method was also used to measure the crystal’s density. Etching experiments were carried out to reveal the etching pattern on the different faces of the crystal. Z-cut plates (10 10 0.3 mm3) were cut from the grown crystals and polished for the transmittance investigation. The transmittance spectrum was measured from the wavelength 200–3000 nm and the absorption edge was determined.
3. Results and discussions 3.1. Crystal growth Like LGS, LGN, LGT and SNGS crystal was grown firstly along /0 0 1S direction. We found it was easy to form polycrystal and could not obtain single crystal however we adjust the parameters of crystal growth. Even when the pulling rate was decreased to 0.3 mm/h, polycrystal still occurred. That means the crystal growth along the /0 0 1S direction is very difficult. At last, perfect SNGS crystal is grown along the /1 0 0S direction. Fig. 1a shows as grown SNGS crystals pulled along direction of /1 0 0S. The grown crystals are transparent and slight yellow in color, no cracks and inclusions are observed in the crystals under microscopic observation.
Fig. 1. (a) SNGS crystals pulled along directions of /1 0 0S; (b), (c) facets of the as grown crystals; (d) sketch of SNGS crystals pulled along directions of /1 0 0S; (e) sketch facets of the as grown crystals.
From the result of crystal growth, the strong facet habit of SNGS crystal has been clearly revealed. Facets of SNGS crystals are {1 0 0}, {0 0 1}, {3 0 2}. As is shown in Fig. 1, {1 0 0} faces form the angles of 1201 and the angle between faces of {0 0 1} and {3 0 2} is 46.71. Because the strong exposure of {1 0 0} faces, the shape of solid–liquid interface is never flat, but always forms an angle of 1201 during the crystal growth process. Fig. 2 is a synchrotron radiation X-ray topographic image taken in Beijing Synchrotron Radiation Laboratory. The shape of solid–liquid interface during the crystal growth process is clearly showed in the
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J. Chen et al. / Journal of Crystal Growth 292 (2006) 404–407
Fig. 2. Synchrotron radiation X-ray topographic image of z-cut SNGS wafer.
picture. Since the solid–liquid interface is never flat, strong stress must exist inside crystal and which might induce crack. Fortunately, we have got no crack crystals in our crystal growth system. The color of grown crystals turned slightly deep when annealed at 1100 1C in atmosphere for 12 h. XRPD analysis confirmed that grown crystals were single phase of the langasite-family structure from top to the bottom. All the diffraction peaks were identified to be those for SNGS and no peaks of a second phase were found. According to the indices of XRPD and using program Jade5.0, the lattice parameters calculated for ˚ c ¼ 5:07998 the crystals are a ¼ 8:28626 0:000911 A, ˚ V ¼ 301:8 A˚ 3 and the density is 4.6456 kg/m3. 0:000481 A, However, using Archimedes method, the density of SNGS crystal has been measured to be 4.6834 kg/m3, which is slightly larger than that of calculated. The XRPD pattern and data for SNGS crystals are given, respectively, in Fig. 3.
Fig. 3. XRPD pattern and (h k l) indices of SNGS crystal.
Fig. 4. Etching patterns of SNGS crystals: (a) x-cut; (b) z-cut; and (c) ycut.
3.2. Etching experiment There are some reports concerning the etching patterns of langasite crystals [5,15,16]. And until now, there are no reports about etching pattern of SNGS crystals. In this study, we demonstrate the etching pattern of SNGS crystals. The patterns (including the shape and orientation) of etching pit depend on the etchant and crystal faces. Therefore, selective etching can be used to identify the orientation of crystal face and crystal quality and also to show the defect distribution of crystals. Etching experiments were performed, respectively, on {1 1 0}, {0 0 1}, {0 1 0} faces which were carefully oriented and polished before etching. The etchant was a mixture of H3PO4 and H2O with the volume ratio of 2:1. The etching was taken in a water-bath which had been maintained at a
temperature at 100 1C for 20 min. The etching patterns observed by microscope are showed in Fig. 4. As we can see, the different faces have different etching patterns. In many cases they are thought to be associated with dislocations and dislocation bundles and which is a suggestion of crystal quality [5,15]. But in our view, they are not indicative of dislocations or other type of defects. By microscope, we observed that all these etching patterns are very popular and arranged regularly. They show a regular symmetrical or geometry appearance. They should be a reflection of the crystal’s structure. In solid state physics orthonormal (Cartesian) for crystals with 32 point group, X, Y, Z are often preferred instead of the crystallographical coordinates a1, a2, a3, c (hexagonal setting). Such definition makes X parallel to the twofold a1-axis, Y to the reciprocal b* vector and Z to the c-axis. And the etch patterns are consistent with the crystals’ symmetrical
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˚ c ¼ 5:07998 0:000481 A, ˚ V¼ a ¼ 8:28626 0:000911 A, 3 3 ˚ 301:8 A and the density is 4.6456 kg/m . And the density measured for SNGS crystal by Archimedes method is 4.6834 kg/m3. Etching patterns on {1 1 0}, {0 0 1}, {0 1 0} faces are given and they show a regular symmetrical or geometry appearance which gives the symmetry information of the crystal. The transmittance spectra showed that the as-grown crystal has good optical quality and the absorption edge is determined to be 268 nm. Acknowledgment This work is supported by the Grant from Item of National Natural Science Foundation of China (50242007). Fig. 5. Transmittance spectra of SNGS crystal.
characteristics. Besides the crystal’s symmetrical characteristics, the etch pattern may associate with elements built-up the crystal and the etchant we selected. 3.3. Transmittance spectrum Z-cut plates (10 10 0.3 mm3) was cut from the grown crystals and polished for the transmittance investigation. The transmittance spectrum was measured from the wavelength 200–3000 nm and the absorption edge was determined. The transmittance spectrum of SNGS crystal with z-cut plates is shown in Fig. 5. We can see that the crystals have good optical quality and the highest transmittance exceeds 86%. The absorption edge is 268 nm, which is smaller than 294 nm measured in Ref. [11]. 4. Conclusions Using the Czochralski method, we have grown the Sr3NbGa3Si2O14 single crystals with clear facets. It is showed that the crystal is easily grown along /1 0 0S direction, and {1 0 0}, {0 0 1} plus {3 0 2} faces are strongly exposed as facets. XRPD analysis confirmed that grown crystals were single phase of the langasite-family structure from top to the bottom. The lattice parameters calculated from the XRPD data for the crystal are
References [1] Yu.V. Pusarevsky, P.A. Senushencov, P.A. Popov, B.B. Mill, IEEE Trans. Ultrason. Ferroelectron. Freq. Control. 42 (1995) 653. [2] E. Chilla, C.M. Flannery, H.J. Fro¨hlich, J. Bohm, R.B. Heimann, M. Hengst, U. Straube, IEEE Ultrason. Sympos. (2002) 377. [3] M.F. Dubovik, I.A. Andreyev, Yu.S. Shmaly, Proceedings of the 1994 IEEE International Freq. Cont. Symposium., p. 43. [4] K. Shimamura, H. Takeda, T. Kohno, T. Fikuda, J. Crystal Growth 163 (1996) 388. [5] J. Bohm, R.B. Heimann, M. Hengst, R. Roewer, J. Schindler, J. Crystal Growth 204 (1999) 128. [6] V.V. Kochurikhin, M. Kumatoriya, K. Shimamura, H. Takagi, T. Fukuda, J. Crystal Growth 181 (1997) 452. [7] M.P. da Cunha, E.L. Adler, D.C. Malocha, IEEE Ultrason. Sympos. (1999) 883. [8] M.M.C. Chou, S. Jen, B.H.T. Chai, IEEE International Freqency Control Symposium and PDA Exhibition, 2001, p. 250. [9] B.H.T. Chai, A.N.P. Bustamance, M. Chou, Proceedings of 2000 IEEE Freqency Control Symposium, p. 163. [10] H. Takeda, J. Satob, T. Kato, K. Kawasakib, H. Morikoshib, K. Shimamuraa, T. Fukudaa, Mater. Res. Bull. 35 (2000) 245. [11] Z. Wang, D. Yuana, X. Cheng, et al., J. Crystal Growth 252 (2003) 236. [12] Z. Wang, D. Yuana, X. Cheng, et al., J. Crystal Growth 253 (2003) 378. [13] Z. Wang, X. Cheng, D. Yuana, et al., J. Crystal Growth 249 (2003) 240. [14] Z. Wang, D. Yuana, Z. Cheng, et al., J. Crystal Growth 253 (2003) 398. [15] I.H. Jung, K.B. Shim, K.H. Auh, T. Fukuda, Mater. Lett. 46 (2000) 354. [16] I.H. Jung, Y.H. Kang, K.B. Shim, A. Yoshikawa, Jpn. J. Appl. Phys. 40 (2001) 5706.
Journal of Crystal Growth 292 (2006) 404–407 www.elsevier.com/locate/jcrysgro
Growth habits and characterization of Sr3NbGa3Si2O14 crystal Jianjun Chen, Erwei Shi, Yanqing Zheng, Haikuan Kong, Hui Chen Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, PR China Available online 9 June 2006
Abstract Ordered piezoelectric Sr3NbGa3Si2O14 (SNGS) single crystal with langasite family structure has been successfully grown with clear facet using Czochralski technique. The growth habit of SNGS crystal is revealed and discussed in detail. It is shown that the crystal is easily grown along /1 0 0S direction, and {1 0 0}, {0 0 1} plus {3 0 2} faces are strongly exposed as facets. Detailed X-ray powder diffraction (XRPD) patterns and indices calculated and observed for the crystal are given. The lattice parameters calculated from the ˚ c ¼ 5:07998 0:000481 A, ˚ V ¼ 301:8 A˚ 3 and the density is 4.6456 kg/m3. The density XRPD data are a ¼ 8:28626 0:000911 A, measured for SNGS crystal by Archimedes method is 4.6834 kg/m3. Etching experiments have been performed on {1 1 0}, {0 1 0} and {0 0 1} faces to observe the etch patterns. The transmittance spectra from 200 to 3000 nm have been measured and the absorption edge is determined to be 268 nm. r 2006 Elsevier B.V. All rights reserved. PACS: 81.10; 61.66.F; 81.70.P; 78.20; 81.05; 82.80 Keywords: A1. Crystal structure; A1. Facet; A1. X-ray diffraction; A2. Czochralski method; B1. Gallium compounds; B2. Piezoelectric materials
1. Introduction From 1980s to now, langasite family (including La3Ga5SiO14, Sr3Ga2Ge4O14, La3Nd0.5Ga5.5O14 and La3Ta0.5Ga5.5O14) with A3BC3D2O14 structure has attracted much attention for their excellent properties in applications of surface acoustic wave, bulk acoustic wave and sensors fields [1–7]. As the further development of research on LGS (La3Ga5SiO14), LGN (La3Nd0.5Ga5.5O14), LGT (La3Ta0.5Ga5.5O14) and SGG (Sr3Ga2Ge4O14), several disadvantage of these materials have been perceived [8]. First, the crystal structure of these compounds is ‘‘disordered.’’ The ‘‘disordered’’ structure results primarily from the fact that two of the different cations in each compound randomly share the same sites in the unit cell. A ‘‘disordered’’ structure causes randomly distributed distortion of the crystal structure, which is affecting the crystal uniformity and reproducibility and leading to the lower than ideally achievable acoustic Q and electromechanical coupling. Second, it is known that LGS, LGN, LGT and SGG melt congruently, but the exact Corresponding author. Tel.: +86 21 69987761; fax: +86 21 59927184.
E-mail addresses: [email protected], [email protected] (J. Chen). 0022-0248/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2006.04.044
phase diagrams have not been reported. The congruent melt points are not located on their stoichiometric composition. Third, for LGS, LGN and LGT, high content of Ga2O3 in these materials makes the crystals cost much higher than aquartz, LiTaO3 and LiNbO3. As with SGG, though the content of Ga2O3 decreases, high content of GeO2 makes the crystal growth much more difficult due to the strong evaporation of GeO2 [6]. Based on the understanding of ‘‘disordered’’ structure, compounds have been found four completely ‘‘ordered’’ langasite structure [9]. They are Sr3NbGa3Si2O14 or SNGS, Sr3TaGa3Si2O14 or STGS, Ca3NbGa3Si2O14 or CNGS and Ca3TaGa3Si2O14 or CTGS. Up to now, there are few reports concerning the growth and properties of ordered single crystals [8,10–14]. In this work, we demonstrate the successful growth of SNGS and reveal the growth habits. Also, the optical properties of the crystal have been measured. 2. Experimental procedure The starting materials used for crystal growth were prepared from a through mixture of 99.99% SrCO3,
ARTICLE IN PRESS J. Chen et al. / Journal of Crystal Growth 292 (2006) 404–407
405
Nb2O5, Ga2O3 and SiO2 powders at stoichiometric composition. The compounds were pressed into blocks and sintered at a temperature of 1300 1C in an atmosphere of air for 24 h to synthesize polycrystalline SNGS through solid state reaction. X-ray powder diffraction (XRPD) data of synthesized material and different parts of the single crystal were collected at room temperature on a Rigaku D/ Max-2550V diffractometer from 101 to 701 (2y) with Cu Ka ˚ Upon identification radiation of wavelength l ¼ 1:5418 A. of the single phase LGS structure by XRPD analysis, the synthesized specimens were charged into the crucible for crystal growth. Single crystal growth was carried out by a conventional induction-heating CZ furnace with an iridium crucible (65 mm in diameter and 45 mm height). An after-heater system made of platinum was installed. The growth atmosphere was a mixture of N2 and 1 vol% O2 gas in order to restrain the evaporation of gallium oxide from the melt during crystal growth. The SNGS single crystal growth runs were performed respectively along /0 0 1S and /1 0 0S directions with LGS seeds. The pulling rate was 1–3 mm/h while the crystal rotation rate was 15–25 rpm. Before crystal growth, the melt of starting materials was maintained about 50 1C above the melting temperature for several hours in order to homogenize the melt. After the growth, the crystal was cooled to room temperature at a rate of 70 1C/h. After the growth, the crystals were identified from top to bottom by XRPD analysis. The crystal’s growth habits were discussed and the lattice parameters and the density of the crystal were calculated from the data of XRPD. Archimedes method was also used to measure the crystal’s density. Etching experiments were carried out to reveal the etching pattern on the different faces of the crystal. Z-cut plates (10 10 0.3 mm3) were cut from the grown crystals and polished for the transmittance investigation. The transmittance spectrum was measured from the wavelength 200–3000 nm and the absorption edge was determined.
3. Results and discussions 3.1. Crystal growth Like LGS, LGN, LGT and SNGS crystal was grown firstly along /0 0 1S direction. We found it was easy to form polycrystal and could not obtain single crystal however we adjust the parameters of crystal growth. Even when the pulling rate was decreased to 0.3 mm/h, polycrystal still occurred. That means the crystal growth along the /0 0 1S direction is very difficult. At last, perfect SNGS crystal is grown along the /1 0 0S direction. Fig. 1a shows as grown SNGS crystals pulled along direction of /1 0 0S. The grown crystals are transparent and slight yellow in color, no cracks and inclusions are observed in the crystals under microscopic observation.
Fig. 1. (a) SNGS crystals pulled along directions of /1 0 0S; (b), (c) facets of the as grown crystals; (d) sketch of SNGS crystals pulled along directions of /1 0 0S; (e) sketch facets of the as grown crystals.
From the result of crystal growth, the strong facet habit of SNGS crystal has been clearly revealed. Facets of SNGS crystals are {1 0 0}, {0 0 1}, {3 0 2}. As is shown in Fig. 1, {1 0 0} faces form the angles of 1201 and the angle between faces of {0 0 1} and {3 0 2} is 46.71. Because the strong exposure of {1 0 0} faces, the shape of solid–liquid interface is never flat, but always forms an angle of 1201 during the crystal growth process. Fig. 2 is a synchrotron radiation X-ray topographic image taken in Beijing Synchrotron Radiation Laboratory. The shape of solid–liquid interface during the crystal growth process is clearly showed in the
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Fig. 2. Synchrotron radiation X-ray topographic image of z-cut SNGS wafer.
picture. Since the solid–liquid interface is never flat, strong stress must exist inside crystal and which might induce crack. Fortunately, we have got no crack crystals in our crystal growth system. The color of grown crystals turned slightly deep when annealed at 1100 1C in atmosphere for 12 h. XRPD analysis confirmed that grown crystals were single phase of the langasite-family structure from top to the bottom. All the diffraction peaks were identified to be those for SNGS and no peaks of a second phase were found. According to the indices of XRPD and using program Jade5.0, the lattice parameters calculated for ˚ c ¼ 5:07998 the crystals are a ¼ 8:28626 0:000911 A, ˚ V ¼ 301:8 A˚ 3 and the density is 4.6456 kg/m3. 0:000481 A, However, using Archimedes method, the density of SNGS crystal has been measured to be 4.6834 kg/m3, which is slightly larger than that of calculated. The XRPD pattern and data for SNGS crystals are given, respectively, in Fig. 3.
Fig. 3. XRPD pattern and (h k l) indices of SNGS crystal.
Fig. 4. Etching patterns of SNGS crystals: (a) x-cut; (b) z-cut; and (c) ycut.
3.2. Etching experiment There are some reports concerning the etching patterns of langasite crystals [5,15,16]. And until now, there are no reports about etching pattern of SNGS crystals. In this study, we demonstrate the etching pattern of SNGS crystals. The patterns (including the shape and orientation) of etching pit depend on the etchant and crystal faces. Therefore, selective etching can be used to identify the orientation of crystal face and crystal quality and also to show the defect distribution of crystals. Etching experiments were performed, respectively, on {1 1 0}, {0 0 1}, {0 1 0} faces which were carefully oriented and polished before etching. The etchant was a mixture of H3PO4 and H2O with the volume ratio of 2:1. The etching was taken in a water-bath which had been maintained at a
temperature at 100 1C for 20 min. The etching patterns observed by microscope are showed in Fig. 4. As we can see, the different faces have different etching patterns. In many cases they are thought to be associated with dislocations and dislocation bundles and which is a suggestion of crystal quality [5,15]. But in our view, they are not indicative of dislocations or other type of defects. By microscope, we observed that all these etching patterns are very popular and arranged regularly. They show a regular symmetrical or geometry appearance. They should be a reflection of the crystal’s structure. In solid state physics orthonormal (Cartesian) for crystals with 32 point group, X, Y, Z are often preferred instead of the crystallographical coordinates a1, a2, a3, c (hexagonal setting). Such definition makes X parallel to the twofold a1-axis, Y to the reciprocal b* vector and Z to the c-axis. And the etch patterns are consistent with the crystals’ symmetrical
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˚ c ¼ 5:07998 0:000481 A, ˚ V¼ a ¼ 8:28626 0:000911 A, 3 3 ˚ 301:8 A and the density is 4.6456 kg/m . And the density measured for SNGS crystal by Archimedes method is 4.6834 kg/m3. Etching patterns on {1 1 0}, {0 0 1}, {0 1 0} faces are given and they show a regular symmetrical or geometry appearance which gives the symmetry information of the crystal. The transmittance spectra showed that the as-grown crystal has good optical quality and the absorption edge is determined to be 268 nm. Acknowledgment This work is supported by the Grant from Item of National Natural Science Foundation of China (50242007). Fig. 5. Transmittance spectra of SNGS crystal.
characteristics. Besides the crystal’s symmetrical characteristics, the etch pattern may associate with elements built-up the crystal and the etchant we selected. 3.3. Transmittance spectrum Z-cut plates (10 10 0.3 mm3) was cut from the grown crystals and polished for the transmittance investigation. The transmittance spectrum was measured from the wavelength 200–3000 nm and the absorption edge was determined. The transmittance spectrum of SNGS crystal with z-cut plates is shown in Fig. 5. We can see that the crystals have good optical quality and the highest transmittance exceeds 86%. The absorption edge is 268 nm, which is smaller than 294 nm measured in Ref. [11]. 4. Conclusions Using the Czochralski method, we have grown the Sr3NbGa3Si2O14 single crystals with clear facets. It is showed that the crystal is easily grown along /1 0 0S direction, and {1 0 0}, {0 0 1} plus {3 0 2} faces are strongly exposed as facets. XRPD analysis confirmed that grown crystals were single phase of the langasite-family structure from top to the bottom. The lattice parameters calculated from the XRPD data for the crystal are
References [1] Yu.V. Pusarevsky, P.A. Senushencov, P.A. Popov, B.B. Mill, IEEE Trans. Ultrason. Ferroelectron. Freq. Control. 42 (1995) 653. [2] E. Chilla, C.M. Flannery, H.J. Fro¨hlich, J. Bohm, R.B. Heimann, M. Hengst, U. Straube, IEEE Ultrason. Sympos. (2002) 377. [3] M.F. Dubovik, I.A. Andreyev, Yu.S. Shmaly, Proceedings of the 1994 IEEE International Freq. Cont. Symposium., p. 43. [4] K. Shimamura, H. Takeda, T. Kohno, T. Fikuda, J. Crystal Growth 163 (1996) 388. [5] J. Bohm, R.B. Heimann, M. Hengst, R. Roewer, J. Schindler, J. Crystal Growth 204 (1999) 128. [6] V.V. Kochurikhin, M. Kumatoriya, K. Shimamura, H. Takagi, T. Fukuda, J. Crystal Growth 181 (1997) 452. [7] M.P. da Cunha, E.L. Adler, D.C. Malocha, IEEE Ultrason. Sympos. (1999) 883. [8] M.M.C. Chou, S. Jen, B.H.T. Chai, IEEE International Freqency Control Symposium and PDA Exhibition, 2001, p. 250. [9] B.H.T. Chai, A.N.P. Bustamance, M. Chou, Proceedings of 2000 IEEE Freqency Control Symposium, p. 163. [10] H. Takeda, J. Satob, T. Kato, K. Kawasakib, H. Morikoshib, K. Shimamuraa, T. Fukudaa, Mater. Res. Bull. 35 (2000) 245. [11] Z. Wang, D. Yuana, X. Cheng, et al., J. Crystal Growth 252 (2003) 236. [12] Z. Wang, D. Yuana, X. Cheng, et al., J. Crystal Growth 253 (2003) 378. [13] Z. Wang, X. Cheng, D. Yuana, et al., J. Crystal Growth 249 (2003) 240. [14] Z. Wang, D. Yuana, Z. Cheng, et al., J. Crystal Growth 253 (2003) 398. [15] I.H. Jung, K.B. Shim, K.H. Auh, T. Fukuda, Mater. Lett. 46 (2000) 354. [16] I.H. Jung, Y.H. Kang, K.B. Shim, A. Yoshikawa, Jpn. J. Appl. Phys. 40 (2001) 5706.