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Preparation of antimony-doped SnO2 nanocrystallites
Materials Research Bulletin 37 (2002) 2453±2458
Preparation of antimony-doped SnO2 nanocrystallites Huaming Yang*, Yuehua Hu, Guanzhou Qiu Department of Mineral Engineering, Research Institute of Inorganic Materials, Central South University, Changsha 410083, PR China (Refereed) Received 4 January 2002; accepted 19 July 2002
Abstract The antimony-doped SnO2 nanocrystallite was synthesised by the co-precipitation reaction and subsequent calcination from the antimony(III) chloride and tin(IV) chloride. The crystal size, pore size distribution and properties of the nanocrystalline powders were examined by differential thermal analysis, thermogravimetric analysis, X-ray diffraction and desorption isotherm(Barrett±Joyner±Halenda method). Calcination of the precipitate powder at 6508C led to the formation of Sb±SnO2 nanocrystallite of 6 nm in crystal size. Most of the pores in the nanocrystallite are about 5±10 nm in diameter. Effect of doped antimony on the crystal size of the nanocrystallite is discussed. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: A. Inorganic compound; A. Nanostructure; B. Chemical synthesis; C. X-ray diffraction; C. Thermogravimetric analysis
1. Introduction SnO2 powders have been attracting much attention since they are highly conducting, transparent and sensitive to reducing gases. They have a wide range of applications in various industries including liquid crystal displays, photo-detectors, gas sensors and conductive ®ller [1±3]. One area of primary importance is the ®eld of conductive materials for its unique electrical property, such as pigments, conductive coatings, coated ®lms, conductive rubber and plastics where the presence of certain heavy metals is undesirable [4,5]. Recently, some researchers have pointed out the *
Corresponding author. Tel.: 86-731-8830549; fax: 86-731-8876862. E-mail address: [email protected] (H. Yang). 0025-5408/02/$ ± see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 5 - 5 4 0 8 ( 0 2 ) 0 0 8 9 1 - 7
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H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458
need for more detailed study including nanocrystalline size, pore size and impurity effect of pure SnO2 [6,7]. The impurity-doped SnO2 powders have been found to be more active as conductive ®llers than pure SnO2 [8,9]. But for their applications as ®llers, ultra®ne particles are required to improve the dispersion in the polymer matrix. In this paper, the synthesis of antimony-doped SnO2 nanocrystallite via the coprecipitation method from the antimony(III) chloride and tin(IV) chloride is reported. The Sb±SnO2 nanocrystallite powder was excellent as a conductive ®ller for conductive rubber and plastics. These results will be reported in a future paper. 2. Experimental The antimony chloride (SbCl3) and tin chloride (SnCl4) were dissolved in hydrochloric acid to form 20% acid solution, the acid solution and 30% NaOH solution were simultaneously dropped to distilled water to obtain the precipitates in a temperature-controlled reactor. Reaction temperature and pH value were maintained at 508C and 1.5±2.0, respectively. Reaction time was 30 min. Then, the precipitates were thoroughly washed with demonised water, and dried at 958C for 24 h to form
Fig. 1. Preparation process of antimony-doped SnO2 nanocrystallite.
H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458
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precursors of the nanocrystallite. The precursors were calcined at 6508C for 1 h in air to prepare the antimony-doped SnO2 nanocrystallites. The amounts of doped antimony are 0.25, 0.50, 0.75, 1.00 and 1.25 wt.%. The preparation process of antimonydoped SnO2 nanocrystallites is shown in Fig. 1. The nanocrystallites were examined by X-ray diffraction (XRD). Simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA) measurements were carried out using an RSZ thermal analysis system in air at a heating rate of 108C/min. a-Al2O3 was used as reference material. The average crystal size of the powder was calculated from diffraction peak widths using the Scherrer formula. Adsorption study of the nanocrystallite was performed on a Autosorb-1 static volume adsorption analyser using N2 as the adsorbent at liquid nitrogen temperature. Adsorption data in the relative pressure(P/P0) range of 0.05±1.0 could be obtained from the nitrogen adsorption±desorption isotherms for the sample. Pore size calculations were made using the Kelvin equation for nitrogen in the form: rp
4:15 ; log P0 =P
(1)
where rp is the Kelvin radius of the pore, P/P0 is the relative pressure of nitrogen. The pore diameter at certain P/P0 can be calculated by Eq. (1). A pore size distribution is defined as the distribution of pore volume with respect to pore diameter of the sample. Desorption isotherm was used to determine the pore size distribution using the Barrett±Joyner±Halenda (BJH) method through the AUTOSORB software in the MICROPORE ANALYSIS SYSTEM. 3. Results and discussion The precursor of antimony-doped SnO2 sample was prepared by the co-precipitate method, corresponding to the following reaction equations: SnCl4 4NaOH ! Sn OH4 4NaCl; SbCl3 3NaOH ! SbO OH 3NaCl H2 O: Thermal analysis of the sample was carried out after the drying process of 1058C for 2 h. Fig. 2 shows TG/DTA curves of the antimony-doped SnO2 precursor, where the sample is 1.0 wt.% antimony-doped SnO2 nanocrystallite. In the DTA curve, a distinct endothermic peak which results from dehydration was evident at 50±2008C. As shown in the TGA curve, the weight loss occurred from ambient to 5008C is directly associated with the reactions Sn OH4 SnO2 2H2 O and 2SbO OH Sb2 O3 H2 O. A weak endothermic peak was observed at around 5508C in the DTA curve, and there exists a little weight increase at the same temperature from the TGA curve, it may be attributed to reaction Sb2 O3 O2 Sb2 O5 . Fig. 3 shows the XRD pattern of Sb±SnO2 nanocrystallite, the main phase of the nanocrystallite is SnO2. The amount of doped antimony was too small to affect XRD
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H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458
Fig. 2. TG/DTA curves of the 1.0 wt.% doped antimony precursor.
Fig. 3. XRD pattern of Sb±SnO2 nanocrystallite.
pattern, but it affects crystal size. The average crystal size is from 5.3 to 7.1 nm in Fig. 4. It is shown that the average crystal size of sample decreases with increasing amount of doped antimony. From the above analysis, it is not clear whether the doped
Fig. 4. Effect of the amount of doped antimony on the crystal size of Sb±SnO2 nanocrystallite.
H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458
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Fig. 5. Pore size distribution curve of the Sb±SnO2 nanocrystallite.
antimony exists as Sb2O5 in SnO2 crystal lattice or other antimony oxides, but there have been reports that Sb5 can be incorporated into the SnO2 crystal and Sn4 in SnO2 can be partially replaced by Sb5 [10,11]. This could imply that the doped antimony prevents SnO2 from crystal growth. The pore size distribution of the Sb±SnO2 nanocrystallite is given in Fig. 5. It is seen that there are two maximum values at 5.3 and 7.5 nm, most of the pores in the nanocrystallite are about 5±10 nm in diameter. It is well known that the pore size is a good re¯ection of the actual particle size [12]. Two maximum values in the pore size distribution of the nanocrystallite is greatly related to the formation of new pores by incorporating Sb5 ion into the SnO2 crystal. 4. Conclusions The antimony-doped SnO2 nanocrystallite was synthesised by the co-precipitation method and subsequent thermal treatment from the antimony chloride and tin chloride. The average crystal size of the nanocrystallite varies from 5.3 to 7.1 nm. It is shown that the average crystal size of samples decreases with increasing amount of doped antimony. Most of the pores in the nanocrystallite are about 5±10 nm in diameter. Acknowledgments This work was supported by the National Science Foundation for Distinguished Young Scholars of China (no. 59925412). References [1] M. Sawada, M. Higuchi, S. Kondo, Jpn. J. Phys. Part I 40 (2001) 3332. [2] C. Xu, J. Tamaki, N. Miura, Sens. Actuators B 147 (1991) 3.
2458 [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458 A.L. Dawar, J.C. Joshi, J. Mater. Sci. 19 (1984) 1. M.R.C. Santos, P.R. Bueno, E. Longo, J. Euro. Ceram. Soc. 21 (2001) 161. D.S. Ginley, C. Bright, Mat. Res. Bull. 25 (2000) 15. P. Holody, R.E. Soltis, J. Hangas, Scripta Mater. 44 (2001) 1821. E. Barrera, T. Viverous, A. Tomas, Sol. Energ. Mater. Sol. Cells 57 (1999) 127. H.M. Yang, G.Z. Qiu, Cailiao Kexue Yu Gongyi 5 (1998) 27. M.J. Van Bommel, W.A. Groen, H.A.M. Vanhal, J. Mater. Sci. 34 (1999) 4803. S.D. Han, H. Yang, L. Wang, Sens. Actuators B 66 (2000) 112. J.M.J. Herrman, J.T. Portefaix, M. Forissier, J. Chem Soc. Faraday 75 (1979) 1346. K. Hellgardt, D. Chadwick, Ind. Eng. Chem. Res. 37 (1998) 405.
Preparation of antimony-doped SnO2 nanocrystallites Huaming Yang*, Yuehua Hu, Guanzhou Qiu Department of Mineral Engineering, Research Institute of Inorganic Materials, Central South University, Changsha 410083, PR China (Refereed) Received 4 January 2002; accepted 19 July 2002
Abstract The antimony-doped SnO2 nanocrystallite was synthesised by the co-precipitation reaction and subsequent calcination from the antimony(III) chloride and tin(IV) chloride. The crystal size, pore size distribution and properties of the nanocrystalline powders were examined by differential thermal analysis, thermogravimetric analysis, X-ray diffraction and desorption isotherm(Barrett±Joyner±Halenda method). Calcination of the precipitate powder at 6508C led to the formation of Sb±SnO2 nanocrystallite of 6 nm in crystal size. Most of the pores in the nanocrystallite are about 5±10 nm in diameter. Effect of doped antimony on the crystal size of the nanocrystallite is discussed. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: A. Inorganic compound; A. Nanostructure; B. Chemical synthesis; C. X-ray diffraction; C. Thermogravimetric analysis
1. Introduction SnO2 powders have been attracting much attention since they are highly conducting, transparent and sensitive to reducing gases. They have a wide range of applications in various industries including liquid crystal displays, photo-detectors, gas sensors and conductive ®ller [1±3]. One area of primary importance is the ®eld of conductive materials for its unique electrical property, such as pigments, conductive coatings, coated ®lms, conductive rubber and plastics where the presence of certain heavy metals is undesirable [4,5]. Recently, some researchers have pointed out the *
Corresponding author. Tel.: 86-731-8830549; fax: 86-731-8876862. E-mail address: [email protected] (H. Yang). 0025-5408/02/$ ± see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 5 - 5 4 0 8 ( 0 2 ) 0 0 8 9 1 - 7
2454
H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458
need for more detailed study including nanocrystalline size, pore size and impurity effect of pure SnO2 [6,7]. The impurity-doped SnO2 powders have been found to be more active as conductive ®llers than pure SnO2 [8,9]. But for their applications as ®llers, ultra®ne particles are required to improve the dispersion in the polymer matrix. In this paper, the synthesis of antimony-doped SnO2 nanocrystallite via the coprecipitation method from the antimony(III) chloride and tin(IV) chloride is reported. The Sb±SnO2 nanocrystallite powder was excellent as a conductive ®ller for conductive rubber and plastics. These results will be reported in a future paper. 2. Experimental The antimony chloride (SbCl3) and tin chloride (SnCl4) were dissolved in hydrochloric acid to form 20% acid solution, the acid solution and 30% NaOH solution were simultaneously dropped to distilled water to obtain the precipitates in a temperature-controlled reactor. Reaction temperature and pH value were maintained at 508C and 1.5±2.0, respectively. Reaction time was 30 min. Then, the precipitates were thoroughly washed with demonised water, and dried at 958C for 24 h to form
Fig. 1. Preparation process of antimony-doped SnO2 nanocrystallite.
H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458
2455
precursors of the nanocrystallite. The precursors were calcined at 6508C for 1 h in air to prepare the antimony-doped SnO2 nanocrystallites. The amounts of doped antimony are 0.25, 0.50, 0.75, 1.00 and 1.25 wt.%. The preparation process of antimonydoped SnO2 nanocrystallites is shown in Fig. 1. The nanocrystallites were examined by X-ray diffraction (XRD). Simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA) measurements were carried out using an RSZ thermal analysis system in air at a heating rate of 108C/min. a-Al2O3 was used as reference material. The average crystal size of the powder was calculated from diffraction peak widths using the Scherrer formula. Adsorption study of the nanocrystallite was performed on a Autosorb-1 static volume adsorption analyser using N2 as the adsorbent at liquid nitrogen temperature. Adsorption data in the relative pressure(P/P0) range of 0.05±1.0 could be obtained from the nitrogen adsorption±desorption isotherms for the sample. Pore size calculations were made using the Kelvin equation for nitrogen in the form: rp
4:15 ; log P0 =P
(1)
where rp is the Kelvin radius of the pore, P/P0 is the relative pressure of nitrogen. The pore diameter at certain P/P0 can be calculated by Eq. (1). A pore size distribution is defined as the distribution of pore volume with respect to pore diameter of the sample. Desorption isotherm was used to determine the pore size distribution using the Barrett±Joyner±Halenda (BJH) method through the AUTOSORB software in the MICROPORE ANALYSIS SYSTEM. 3. Results and discussion The precursor of antimony-doped SnO2 sample was prepared by the co-precipitate method, corresponding to the following reaction equations: SnCl4 4NaOH ! Sn OH4 4NaCl; SbCl3 3NaOH ! SbO OH 3NaCl H2 O: Thermal analysis of the sample was carried out after the drying process of 1058C for 2 h. Fig. 2 shows TG/DTA curves of the antimony-doped SnO2 precursor, where the sample is 1.0 wt.% antimony-doped SnO2 nanocrystallite. In the DTA curve, a distinct endothermic peak which results from dehydration was evident at 50±2008C. As shown in the TGA curve, the weight loss occurred from ambient to 5008C is directly associated with the reactions Sn OH4 SnO2 2H2 O and 2SbO OH Sb2 O3 H2 O. A weak endothermic peak was observed at around 5508C in the DTA curve, and there exists a little weight increase at the same temperature from the TGA curve, it may be attributed to reaction Sb2 O3 O2 Sb2 O5 . Fig. 3 shows the XRD pattern of Sb±SnO2 nanocrystallite, the main phase of the nanocrystallite is SnO2. The amount of doped antimony was too small to affect XRD
2456
H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458
Fig. 2. TG/DTA curves of the 1.0 wt.% doped antimony precursor.
Fig. 3. XRD pattern of Sb±SnO2 nanocrystallite.
pattern, but it affects crystal size. The average crystal size is from 5.3 to 7.1 nm in Fig. 4. It is shown that the average crystal size of sample decreases with increasing amount of doped antimony. From the above analysis, it is not clear whether the doped
Fig. 4. Effect of the amount of doped antimony on the crystal size of Sb±SnO2 nanocrystallite.
H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458
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Fig. 5. Pore size distribution curve of the Sb±SnO2 nanocrystallite.
antimony exists as Sb2O5 in SnO2 crystal lattice or other antimony oxides, but there have been reports that Sb5 can be incorporated into the SnO2 crystal and Sn4 in SnO2 can be partially replaced by Sb5 [10,11]. This could imply that the doped antimony prevents SnO2 from crystal growth. The pore size distribution of the Sb±SnO2 nanocrystallite is given in Fig. 5. It is seen that there are two maximum values at 5.3 and 7.5 nm, most of the pores in the nanocrystallite are about 5±10 nm in diameter. It is well known that the pore size is a good re¯ection of the actual particle size [12]. Two maximum values in the pore size distribution of the nanocrystallite is greatly related to the formation of new pores by incorporating Sb5 ion into the SnO2 crystal. 4. Conclusions The antimony-doped SnO2 nanocrystallite was synthesised by the co-precipitation method and subsequent thermal treatment from the antimony chloride and tin chloride. The average crystal size of the nanocrystallite varies from 5.3 to 7.1 nm. It is shown that the average crystal size of samples decreases with increasing amount of doped antimony. Most of the pores in the nanocrystallite are about 5±10 nm in diameter. Acknowledgments This work was supported by the National Science Foundation for Distinguished Young Scholars of China (no. 59925412). References [1] M. Sawada, M. Higuchi, S. Kondo, Jpn. J. Phys. Part I 40 (2001) 3332. [2] C. Xu, J. Tamaki, N. Miura, Sens. Actuators B 147 (1991) 3.
2458 [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
H. Yang et al. / Materials Research Bulletin 37 (2002) 2453±2458 A.L. Dawar, J.C. Joshi, J. Mater. Sci. 19 (1984) 1. M.R.C. Santos, P.R. Bueno, E. Longo, J. Euro. Ceram. Soc. 21 (2001) 161. D.S. Ginley, C. Bright, Mat. Res. Bull. 25 (2000) 15. P. Holody, R.E. Soltis, J. Hangas, Scripta Mater. 44 (2001) 1821. E. Barrera, T. Viverous, A. Tomas, Sol. Energ. Mater. Sol. Cells 57 (1999) 127. H.M. Yang, G.Z. Qiu, Cailiao Kexue Yu Gongyi 5 (1998) 27. M.J. Van Bommel, W.A. Groen, H.A.M. Vanhal, J. Mater. Sci. 34 (1999) 4803. S.D. Han, H. Yang, L. Wang, Sens. Actuators B 66 (2000) 112. J.M.J. Herrman, J.T. Portefaix, M. Forissier, J. Chem Soc. Faraday 75 (1979) 1346. K. Hellgardt, D. Chadwick, Ind. Eng. Chem. Res. 37 (1998) 405.