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Growth, thermal and optical properties of a new nonlinear optical crystal: ZnBi2B2O7
ARTICLE IN PRESS Journal of Crystal Growth 311 (2009) 3476–3478
Contents lists available at ScienceDirect
Journal of Crystal Growth journal homepage: www.elsevier.com/locate/jcrysgro
Growth, thermal and optical properties of a new nonlinear optical crystal: ZnBi2B2O7 Nan Li a,b, Peizhen Fu a,, Yicheng Wu a, Jianxiu Zhang a a b
Beijing Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China Graduate University of Chinese Academy of Sciences, Beijing 100039, China
a r t i c l e in f o
a b s t r a c t
Article history: Received 14 January 2009 Received in revised form 7 April 2009 Accepted 15 April 2009 Communicated by R.S. Feigelson Available online 22 April 2009
Single crystals of ZnBi2B2O7 (ZBBO) have been successfully grown by the top-seeded growth method from a high-temperature melt. The crystal was colorless and transparent with size of 15 10 5 mm3. The orientation of ZBBO crystal has been discussed. The melting point, molar enthalpy of fusion, and molar entropy of fusion of the crystal were determined to be 964.02 K, 110680.36 J mol1, and 113.92 J K1 mol1, respectively. The transparency range of the crystal extends from 370 to 2100 nm. & 2009 Elsevier B.V. All rights reserved.
PACS: 81.10.Fq 81.10.Aj 42.70.Mp Keywords: A1. X-ray diffraction A2. Growth from melt B1. Bismuth and zincum borate B2. Nonlinear optical materials
1. Introduction In recent years, binary bismuth borates have been of continuing interest for their excellent optical properties, especially, the BiB3O6 [1–4] crystal that displays large nonlinear optical (NLO) efficiency. Barbier and Cranswick had undertaken a systematic investigation about MO–Bi2O3–B2O3 [5] system and found a series of new phases, such as ZnBi2B2O7 (ZBBO), CaBi2B2O7, CaBiGaB2O7 [6], BaBiBO4, etc. They determined the crystal structure by neutron diffraction. Then Li Ming obtained the single crystal using spontaneous nucleation method and solved the crystal structure accurately by single-crystal X-ray diffraction (XRD) measurements [7]. The ZnBi2B2O7 belongs to orthorhombic system, space group Pba2, with lattice parameters of a=10.819(2) A˚, b=11.023(2) A˚, c=4.890(1) A˚ and its powder second harmonic generation efficiency (deff) is about 4 times as large as that of KDP. ZBBO has a potential application in frequency conversion. However, the growth of large ZBBO crystal and its physical properties have not been reported in any literature till now. In this
Corresponding author. Tel.: +86 10 82543719; fax: +86 10 82543709.
E-mail address: [email protected] (P. Fu). 0022-0248/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2009.04.016
paper, the growth of ZBBO crystal with large sizes and high optical quality and some of its important physical parameters, which have great influence on crystal growth and processing, even affect the application of the materials, are first reported.
2. Synthesis and crystal growth Because of its congruent melting, ZBBO crystal can be grown from its stoichiometric melt by the top-seeded method. Polycrystalline samples of ZBBO were synthesized by using hightemperature solid-state techniques. All reagents were of analytical grade. The raw materials were prepared by mixing ZnO, Bi2O3, H3BO3 according to the stoichiometric composition. The mixture was ground carefully to ensure homogeneous mixing, and then was gradually heated to 650 1C, kept for 24 h. The product was the raw materials for crystal growth, which would be melt in the platinum crucible at 800 1C for later crystal growth. The growth experiments were carried out in a resistance-heated furnace. At the beginning of our experiment, a platinum wire attached to an alumina shaft was used to initiate crystallization to obtain seeds. The temperature was raised at about 100–150 1C/h to 800 1C and overheated for 5–8 h to ensure the solution melt completely and mix homogeneously. After the melt was first cooled at a rate of
ARTICLE IN PRESS N. Li et al. / Journal of Crystal Growth 311 (2009) 3476–3478
10 1C/h to 680 1C, a platinum wire was slowly inserted into the furnace and dipped into the melt, then the cooling rate was changed to 1 1C/h. During the cooling process, some pieces of rhombic crystals formed and attached on the platinum wire. The initial products were not good enough to be the seeds for crystal growth, and we did the former experiments repeatedly. Finally, we obtained some colorless, transparent plate crystals. The obtained crystals were chemically stable, not hygroscopic, and could be used as seeds. Since crystal growth temperature was only about 690 1C, Czochralski method cannot be observed because of low temperature; as a result we adopted the top-seeded growth method for crystal growth. The crucible with the charge was placed into the furnace and heated gradually to 800 1C. After the melt was stirred with a platinum sheet for 12 h at 800 1C for overheating the melt, decreasing the temperature slowly to 680 1C, the test-seeded technique was employed to measure the saturation temperature of the melt (about 670 1C). At 5 1C higher than the saturation temperature, a seed crystal was slowly inserted into the furnace and put into contact with the surface of the melt. The temperature was held for 30 min to melt the surface of the seed crystal and then decreased to the saturation temperature within 20 min. After the temperature was held for 24 h at the saturation temperature, the cooling rate was set at a rate of 0.2 1C/day, and the growing crystal was rotated at a rate of 10 rpm. After the growth was completed, the crystal was drawn out of the melt and cooled to room temperature at a rate of 30 1C/h. Finally, the ZBBO crystal with a size 15 10 5 mm3 was obtained. A few typically grown crystals are shown in Fig. 1(a).
a
3477
3. Result and discussion 3.1. X-ray powder diffraction The products of phase stability experiments were identified from powder X-ray diffraction patterns obtained by a Bruker D8 ADVANCE X-ray diffractometer with CuKa radiation over a 2y range 7–701 with a step size of 0.031 at a rate of 1 s/step, and compared to simulated patterns about the structure reported by Li Ming et al. Fig. 2 shows the XRD patterns of the pulverized ZBBO crystal. All the diffraction peaks can be indexed with the Pba2 symmetry, which confirms that the structure of the as-grown crystal corresponds to the ZBBO. Moreover, no parasitic phases were observed, suggesting that pure ZBBO crystal has been obtained with this technique. The lattice parameters were calculated to be a=10.82(7) A˚, b=11.02(5) A˚, c=4.89(0) A˚, which agrees with those of structural determination. 3.2. Orientation It is extremely important to know the orientation of any anisotropic material since all properties are highly dependent on the sample orientation and the crystals must therefore be exactly orientated when been cut and polished. As shown in Fig. 1(a), the as-grown crystal presented some cylinders and inclines, and all of the faces were oriented by X-ray diffraction goniometer. As shown in Fig. 1(b), the [0 0 1] direction is plumb with page surface, and the plane index is labeled in Fig. 1(b). 3.3. Melting point and enthalpy of fusion measurements A differential scanning calorimeter (DSC) made by NETZSCH company (NETZSCH DSC 200PC) was used to measure the melting point and enthalpy of fusion of ZBBO crystal. A small piece of crystal weighing 7.8 mg was used for the DSC measurement. The sample was kept in a platinum crucible and another one with aAl2O3 powder was used as the reference crucible when they were heated together at a constant rate of 10 K/min from 373 to 1073 K. Fig. 3 shows the DSC curve of the ZBBO crystal. A single sharp endothermic peak is in the range from 964.02 to 980.50 K in Fig. 3. This peak exhibits the characteristics of a first-order phase transition with a peak temperature at 971.59 K. Evidence of the fusion of the ZBBO crystal was found in the sample cell after the
(100)
(111)
The experiment XRD pattern (111)
(110)
Intensity / Count
b
(120)
(010) (120) (110) (110) (111)
The simulated XRD pattern
b
C
(100) 10 a
Fig. 1. (a) The photograph of as-grown ZBBO crystal. (b) Morphology of the ZBBO crystal.
20
30
40
50
60
70
2theta/deg. Fig. 2. XRD pattern of ZBBO observed from pulverized crystal and simulated from single-crystal data.
ARTICLE IN PRESS 3478
N. Li et al. / Journal of Crystal Growth 311 (2009) 3476–3478
40
80
964.02k
70
Heat flow/mw
20 10 0
80
60 50 40 30
70
Transmittance (%)
Transimittance (%)
30
20
60 50 40 30 20 10 0
10
-10
360 380 400 420 440 460 480 500 520 540 560 580 600
Wavelength (nm)
0 500
-20
1000
1500
2000
2500
3000
Wavelength (nm)
400
500
600
700 800 900 Temperature/K
1000
1100
Fig. 3. DSC curve of grown ZBBO crystal.
Fig. 4. Transmission spectrum of ZBBO crystal.
transparent range of ZBBO covers 370–2500 nm. This valuable property may be very important for NLO applications of this borate crystal.
Table 1 Thermodynamic parameters of ZBBO crystal gained from DSC measurement.
4. Conclusions Thermodynamic parameters
Values
Tm (K) DfusHm (J mol1) DfusSm (J K1 mol1)
964.02 110,680.36 113.92
DSC measurement. The transition can be attributed to a solid–liquid phase change. The set off temperature 964.02 K is identified as the melting point of ZBBO crystal. The molar enthalpy of fusion DfusHm single-crystal ZBBO was derived from the DSC curve using the area integration method included in the DSC analytical software provided by the NETZSCH. The molar entropy of fusion DfusSm was calculated using the following thermodynamic equation:
Dfus Sm ¼
Dfus Hm Tm
The thermal properties of single-crystal ZBBO were carefully investigated by measuring the melting point, molar enthalpy of fusion, and molar entropy of fusion. The transmission spectrum shows that the ZBBO crystal is transparent in the range 370–2500 nm. These properties make ZBBO attractive for the continued research and development as a new NLO material. Investigations on the linear and nonlinear optical properties of ZBBO crystal are in progress.
Acknowledgement This work was supported by the National Natural Science Foundation of China (Grant no. 50672104).
,
where Tm is the melting point of the ZBBO crystal. The calculated results are listed in Table 1. 3.4. Ultraviolet spectrum measurement The transmission spectrum of ZBBO was recorded at room temperature by a Perkin Elmer Lambda 900 UV/Vis/NIR spectrophotometer, which can operate over the range 185–3500 nm. The measurement range extended from 300 to 3100 nm. The optical absorption spectra of ZBBO in Fig. 4 show that the UV cut-off wavelength of this crystal occurs at 350 nm. It can be seen that the
References [1] H. Hellwig, J. Liebertz, L. Bohat, Solid State Communications 109 (1998) 249–251. [2] B. Teng, J. Wang, Z. Wang, X. Hu, H. Jiang, H. Liu, X. Cheng, S. Dong, Y. Liu, Z. Shao, Journal of Crystal Growth 233 (2001) 282–286. [3] A. Brenier, I.V. Kityk, A. Majchrowski, Optics Communications 203 (2002) 125–132. [4] V. Ruseva, J. Hald, Optics Communications 236 (2004) 219–223. [5] J. Barbier, L.M.D. Cranswick, Journal of Solid State Chemistry 179 (2006) 3958–3964. [6] J. Barbier, N. Penin, L.M. Cranswick, Chemistry of Materials 17 (2005) 3130–3136. [7] Li Ming, Chen Xue-an, Chang Xin-an, Zhang He-gui, Xiao Wei-qiang, Journal of Synthetic Crystal 36 (2007) 1005–1009.
Contents lists available at ScienceDirect
Journal of Crystal Growth journal homepage: www.elsevier.com/locate/jcrysgro
Growth, thermal and optical properties of a new nonlinear optical crystal: ZnBi2B2O7 Nan Li a,b, Peizhen Fu a,, Yicheng Wu a, Jianxiu Zhang a a b
Beijing Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China Graduate University of Chinese Academy of Sciences, Beijing 100039, China
a r t i c l e in f o
a b s t r a c t
Article history: Received 14 January 2009 Received in revised form 7 April 2009 Accepted 15 April 2009 Communicated by R.S. Feigelson Available online 22 April 2009
Single crystals of ZnBi2B2O7 (ZBBO) have been successfully grown by the top-seeded growth method from a high-temperature melt. The crystal was colorless and transparent with size of 15 10 5 mm3. The orientation of ZBBO crystal has been discussed. The melting point, molar enthalpy of fusion, and molar entropy of fusion of the crystal were determined to be 964.02 K, 110680.36 J mol1, and 113.92 J K1 mol1, respectively. The transparency range of the crystal extends from 370 to 2100 nm. & 2009 Elsevier B.V. All rights reserved.
PACS: 81.10.Fq 81.10.Aj 42.70.Mp Keywords: A1. X-ray diffraction A2. Growth from melt B1. Bismuth and zincum borate B2. Nonlinear optical materials
1. Introduction In recent years, binary bismuth borates have been of continuing interest for their excellent optical properties, especially, the BiB3O6 [1–4] crystal that displays large nonlinear optical (NLO) efficiency. Barbier and Cranswick had undertaken a systematic investigation about MO–Bi2O3–B2O3 [5] system and found a series of new phases, such as ZnBi2B2O7 (ZBBO), CaBi2B2O7, CaBiGaB2O7 [6], BaBiBO4, etc. They determined the crystal structure by neutron diffraction. Then Li Ming obtained the single crystal using spontaneous nucleation method and solved the crystal structure accurately by single-crystal X-ray diffraction (XRD) measurements [7]. The ZnBi2B2O7 belongs to orthorhombic system, space group Pba2, with lattice parameters of a=10.819(2) A˚, b=11.023(2) A˚, c=4.890(1) A˚ and its powder second harmonic generation efficiency (deff) is about 4 times as large as that of KDP. ZBBO has a potential application in frequency conversion. However, the growth of large ZBBO crystal and its physical properties have not been reported in any literature till now. In this
Corresponding author. Tel.: +86 10 82543719; fax: +86 10 82543709.
E-mail address: [email protected] (P. Fu). 0022-0248/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2009.04.016
paper, the growth of ZBBO crystal with large sizes and high optical quality and some of its important physical parameters, which have great influence on crystal growth and processing, even affect the application of the materials, are first reported.
2. Synthesis and crystal growth Because of its congruent melting, ZBBO crystal can be grown from its stoichiometric melt by the top-seeded method. Polycrystalline samples of ZBBO were synthesized by using hightemperature solid-state techniques. All reagents were of analytical grade. The raw materials were prepared by mixing ZnO, Bi2O3, H3BO3 according to the stoichiometric composition. The mixture was ground carefully to ensure homogeneous mixing, and then was gradually heated to 650 1C, kept for 24 h. The product was the raw materials for crystal growth, which would be melt in the platinum crucible at 800 1C for later crystal growth. The growth experiments were carried out in a resistance-heated furnace. At the beginning of our experiment, a platinum wire attached to an alumina shaft was used to initiate crystallization to obtain seeds. The temperature was raised at about 100–150 1C/h to 800 1C and overheated for 5–8 h to ensure the solution melt completely and mix homogeneously. After the melt was first cooled at a rate of
ARTICLE IN PRESS N. Li et al. / Journal of Crystal Growth 311 (2009) 3476–3478
10 1C/h to 680 1C, a platinum wire was slowly inserted into the furnace and dipped into the melt, then the cooling rate was changed to 1 1C/h. During the cooling process, some pieces of rhombic crystals formed and attached on the platinum wire. The initial products were not good enough to be the seeds for crystal growth, and we did the former experiments repeatedly. Finally, we obtained some colorless, transparent plate crystals. The obtained crystals were chemically stable, not hygroscopic, and could be used as seeds. Since crystal growth temperature was only about 690 1C, Czochralski method cannot be observed because of low temperature; as a result we adopted the top-seeded growth method for crystal growth. The crucible with the charge was placed into the furnace and heated gradually to 800 1C. After the melt was stirred with a platinum sheet for 12 h at 800 1C for overheating the melt, decreasing the temperature slowly to 680 1C, the test-seeded technique was employed to measure the saturation temperature of the melt (about 670 1C). At 5 1C higher than the saturation temperature, a seed crystal was slowly inserted into the furnace and put into contact with the surface of the melt. The temperature was held for 30 min to melt the surface of the seed crystal and then decreased to the saturation temperature within 20 min. After the temperature was held for 24 h at the saturation temperature, the cooling rate was set at a rate of 0.2 1C/day, and the growing crystal was rotated at a rate of 10 rpm. After the growth was completed, the crystal was drawn out of the melt and cooled to room temperature at a rate of 30 1C/h. Finally, the ZBBO crystal with a size 15 10 5 mm3 was obtained. A few typically grown crystals are shown in Fig. 1(a).
a
3477
3. Result and discussion 3.1. X-ray powder diffraction The products of phase stability experiments were identified from powder X-ray diffraction patterns obtained by a Bruker D8 ADVANCE X-ray diffractometer with CuKa radiation over a 2y range 7–701 with a step size of 0.031 at a rate of 1 s/step, and compared to simulated patterns about the structure reported by Li Ming et al. Fig. 2 shows the XRD patterns of the pulverized ZBBO crystal. All the diffraction peaks can be indexed with the Pba2 symmetry, which confirms that the structure of the as-grown crystal corresponds to the ZBBO. Moreover, no parasitic phases were observed, suggesting that pure ZBBO crystal has been obtained with this technique. The lattice parameters were calculated to be a=10.82(7) A˚, b=11.02(5) A˚, c=4.89(0) A˚, which agrees with those of structural determination. 3.2. Orientation It is extremely important to know the orientation of any anisotropic material since all properties are highly dependent on the sample orientation and the crystals must therefore be exactly orientated when been cut and polished. As shown in Fig. 1(a), the as-grown crystal presented some cylinders and inclines, and all of the faces were oriented by X-ray diffraction goniometer. As shown in Fig. 1(b), the [0 0 1] direction is plumb with page surface, and the plane index is labeled in Fig. 1(b). 3.3. Melting point and enthalpy of fusion measurements A differential scanning calorimeter (DSC) made by NETZSCH company (NETZSCH DSC 200PC) was used to measure the melting point and enthalpy of fusion of ZBBO crystal. A small piece of crystal weighing 7.8 mg was used for the DSC measurement. The sample was kept in a platinum crucible and another one with aAl2O3 powder was used as the reference crucible when they were heated together at a constant rate of 10 K/min from 373 to 1073 K. Fig. 3 shows the DSC curve of the ZBBO crystal. A single sharp endothermic peak is in the range from 964.02 to 980.50 K in Fig. 3. This peak exhibits the characteristics of a first-order phase transition with a peak temperature at 971.59 K. Evidence of the fusion of the ZBBO crystal was found in the sample cell after the
(100)
(111)
The experiment XRD pattern (111)
(110)
Intensity / Count
b
(120)
(010) (120) (110) (110) (111)
The simulated XRD pattern
b
C
(100) 10 a
Fig. 1. (a) The photograph of as-grown ZBBO crystal. (b) Morphology of the ZBBO crystal.
20
30
40
50
60
70
2theta/deg. Fig. 2. XRD pattern of ZBBO observed from pulverized crystal and simulated from single-crystal data.
ARTICLE IN PRESS 3478
N. Li et al. / Journal of Crystal Growth 311 (2009) 3476–3478
40
80
964.02k
70
Heat flow/mw
20 10 0
80
60 50 40 30
70
Transmittance (%)
Transimittance (%)
30
20
60 50 40 30 20 10 0
10
-10
360 380 400 420 440 460 480 500 520 540 560 580 600
Wavelength (nm)
0 500
-20
1000
1500
2000
2500
3000
Wavelength (nm)
400
500
600
700 800 900 Temperature/K
1000
1100
Fig. 3. DSC curve of grown ZBBO crystal.
Fig. 4. Transmission spectrum of ZBBO crystal.
transparent range of ZBBO covers 370–2500 nm. This valuable property may be very important for NLO applications of this borate crystal.
Table 1 Thermodynamic parameters of ZBBO crystal gained from DSC measurement.
4. Conclusions Thermodynamic parameters
Values
Tm (K) DfusHm (J mol1) DfusSm (J K1 mol1)
964.02 110,680.36 113.92
DSC measurement. The transition can be attributed to a solid–liquid phase change. The set off temperature 964.02 K is identified as the melting point of ZBBO crystal. The molar enthalpy of fusion DfusHm single-crystal ZBBO was derived from the DSC curve using the area integration method included in the DSC analytical software provided by the NETZSCH. The molar entropy of fusion DfusSm was calculated using the following thermodynamic equation:
Dfus Sm ¼
Dfus Hm Tm
The thermal properties of single-crystal ZBBO were carefully investigated by measuring the melting point, molar enthalpy of fusion, and molar entropy of fusion. The transmission spectrum shows that the ZBBO crystal is transparent in the range 370–2500 nm. These properties make ZBBO attractive for the continued research and development as a new NLO material. Investigations on the linear and nonlinear optical properties of ZBBO crystal are in progress.
Acknowledgement This work was supported by the National Natural Science Foundation of China (Grant no. 50672104).
,
where Tm is the melting point of the ZBBO crystal. The calculated results are listed in Table 1. 3.4. Ultraviolet spectrum measurement The transmission spectrum of ZBBO was recorded at room temperature by a Perkin Elmer Lambda 900 UV/Vis/NIR spectrophotometer, which can operate over the range 185–3500 nm. The measurement range extended from 300 to 3100 nm. The optical absorption spectra of ZBBO in Fig. 4 show that the UV cut-off wavelength of this crystal occurs at 350 nm. It can be seen that the
References [1] H. Hellwig, J. Liebertz, L. Bohat, Solid State Communications 109 (1998) 249–251. [2] B. Teng, J. Wang, Z. Wang, X. Hu, H. Jiang, H. Liu, X. Cheng, S. Dong, Y. Liu, Z. Shao, Journal of Crystal Growth 233 (2001) 282–286. [3] A. Brenier, I.V. Kityk, A. Majchrowski, Optics Communications 203 (2002) 125–132. [4] V. Ruseva, J. Hald, Optics Communications 236 (2004) 219–223. [5] J. Barbier, L.M.D. Cranswick, Journal of Solid State Chemistry 179 (2006) 3958–3964. [6] J. Barbier, N. Penin, L.M. Cranswick, Chemistry of Materials 17 (2005) 3130–3136. [7] Li Ming, Chen Xue-an, Chang Xin-an, Zhang He-gui, Xiao Wei-qiang, Journal of Synthetic Crystal 36 (2007) 1005–1009.