Nanocrystalline zirconium (IV) tungstate is prepared by chemical coprecipitation method using ethylene diamine tetra acetic acid as the templating agent. Elemental composition is determined by EDS. The characteristic bonding position is identified using FTIR. XRD is used to find the theoritical value of size and phase identification using JCPDS. Morphology is examined using SEM and HRTEM. UV absorption at 260 nm corresponds to an energy gap of 4.48 eV, characteristic of semiconducting nanoparticles.
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Beena, B.

Manoj, S.

Journal of Nano- and Electronic Physics

Electronic Sumy State University Institutional Repository

   J. Nano- Electron. Phys. 3 (2011) No1, P.179-184  2011 SumDU (Sumy State University)   179 PACS numbers: 71.20.Be, 68.37.Og   SYNTHESIS AND CHARACTERIZATION OF NOVEL NANOCRYSTALLINE ZIRCONIUM (IV) TUNGSTATE SEMICONDUCTOR   S. Manoj, B. Beena   Department of Chemistry, D.B. College,   Sasthamcotta, Kollam, Kerala, India 690 521  E-mail: beenadbc@gmail.com  Nanocrystalline zirconium (IV) tungstate is prepared by chemical coprecipitation method using ethylene diamine tetra acetic acid as the templating agent. Elemental composition is determined by EDS. The characteristic bonding position is identified using FTIR.XRD is used to find the theoritical value of size and phase identification using  JCPDS.  Morphology  is  examined  using  SEM and  HRTEM.  UV  absorption  at  260 nm corresponds to an energy gap of 4.48 eV, characteristic of semiconducting nanoparticles.   Keywords: ZIRCONIUM (IV) TUNGSTATE, SEMICONDUCTOR, BAND GAP, EDS, HRTEM, ZIRCONIA, TUNGSTEN OXIDE  (Received 04 February 2011, in final form 20 March 2011)  1. INTRODUCTION  Metal oxide semiconductor nanomaterials are usable as semiconducting gas sensors  because they have many advantage such as  small  diamensions,  low cost, low power consumption, on-line operation and high compatibility with microelectronic processing. These include SnO2, WO3, ZrO2, WO3, etc. These materials have non-stoichiometric structures, so free electrons orginating from oxygen vacancies contribute to electronic conductivity [1]. Tungsten oxide  is  an  n-type  semiconductor  with  energy  gap  in  the  range  of   5.59 - 5.7 eV. Therefore, it is suitable for applications such as electrochromic, optochromic and gasochromic coatings for smart windows, information display and various sensors [2]. Many researchers have studied the sensor, magnetic and electric properties of WO3 prepared by heat treatment,  arc  discharge,  sol  gel  etc  with  different  morphology  and  structure. These materals are studied in different forms such as nanowires, nanorods, dopped with transition metal, etc [3, 4, 5, 6] which are either in the isolated form or in mixed oxide form. These mixed oxide forms are non-stoichiometric forms with varying metal concentration.  In the present work, nanoform of zirconium (IV) tungstate is prepared in the stoichiometric form by chemical coprecipitation method. The material is well characterized using EDS, XRD, FTIR, SEM and HRTEM. UV spectrum is used to find the optical band gap.    180 S. MANOJ, B. BEENA    2. EXPERIMENTAL   2.1 Preparation of zirconium (IV) tungstate in the nanoform  The  nanoform  of  zirconium  (IV)  tungstate  is  synthesized  by  chemical  coprecipitation method. In this, equimolar aqueous solutions of zirconium oxychloride  and  sodium  tungstate  in  the  volume  ratio  1:2  is  added  to  ethylene diamine tetra acetic acid template at a pH ~ 1.5 with constant stirring using a magnetic stirrer. The precipitate of zirconium (IV) tungstate is separated by filtration and washed with distilled water. It is then converted to the hydrogen form by immersing in 1M HCl.   2.2 Characterization of the material  EDS spectrum of the material was taken using JOEL Model JED-2300. X-ray diffractogram (2ș   10 - 90q)  was  obtained  on  XPERT-PRO  powder  diffractometer with Cu-KĮ radiation. The FTIR spectrum was recorded using KBr wafer on the Thermo Nicolet FTIR model AVATAR 370 DTGS.SEM was taken from BJOEL Model JSM-6390LV.PHILIPS Model CM 200 was used to take the HRTEM. The absorption spectra were recorded at room temperature using SHIMADSU UV-2550 UV Visible spectrophoto-meter.  2.3 Results and Discussion  EDS spectrum shows the presence of zirconium and tungsten in the stichiometric proportion. The empirical formula calculated is Zr2W3O13. The EDS  spectrum  is  shown  in  figure  1.  The  X-ray  diffractions  of  the  nanoparticles of zirconium (IV) tungstate consist (figure 2) of cubic phases of ZrW2O8, agreeing with the JCPDS file No.89-6670 with small amount of isolated cubic zirconia (JCPDS file No.89-9069) and hexagonal tungsten oxide (JCPDS file No.82-2459).     Fig. 1 – EDS of zirconium (IV) tungstate      SYNTHESIS AND CHARACTERIZATION OF NOVEL… 181    Fig. 2 – XRD of zirconium (IV) tungstate   FTIR spectrum (figure 3) shows bands due to water molecules/surface hydroxyl groups (~ 3415 cm – 1, 1637 cm – 1, 1380 cm – 1). Band in the region 837  cm  is  due  to  24WO  species  and  at  711  cm – 1 is  due  to  W-O  stretching  vibration. Band in the region 493 cm – 1 is due to Zr-O vibration [7, 8].  SEM and HRTEM shown in figure 4 and figure 5 are used to examine the morphology of the nanomaterial. The spherical nature of the particles is revealed from both the SEM and HRTEM. Further from HRTEM it is seen that the particles are less than 50 nm in size.  UV Spectrum shown in figure 6 gives information about excitonic or interband transition of nanocrystalline material. It shows absorption at 260 nm which corresponds to an energy gap of 4.77 eV. The fundamental absorption which corresponds to electron excitation from the valence band to the conduction band is used to determine the nature and the value of optical band gap. The relation between absoption coefficient (D) and incident photon energy (hQ) is given by the Tauc relation,   (DhQ)1/n   A(hQ – Eg),   where A is  a  constant,  Eg is the band gap of the material, D, is the absorption coefficient and the exponent ‘n’ depends on the type of transition [9]. The value of band gap can be determined by plotting (DhQ)1/n versus hȞ (figure 7) and extrapolating the straight line portion of the graph to hȞ axis. The direct allowed band gap calculated is 4.48 eV. A more straight forward method of determining an approximate value of band gap regardless of band structure is by plotting the absorbance versus energy, and extrapolating to zero  absorbance  which  in  this  case  gives  a  band  gap  of  4.49  eV.  Bulk  ZrW2O8 is an insulating dielectric ceramic and the calculated band gap for D-phase is 2.81 eV and for Ȗ-phase is 1.74 eV [10]. The increase in the band gap  to  4.48  eV  of  this  material  is  due  to  small  size  and  the  quantum  confinement limiting. The quantum confinement effect is expected for semiconducting nanoparticles and the absorption edge will be shifted to high energy with decrease in particle size [11].    182 S. MANOJ, B. BEENA      Fig. 3 – FTIR of zirconium (IV) tungstate     Fig. 4 – SEM of zirconium (IV) tungstate     SYNTHESIS AND CHARACTERIZATION OF NOVEL… 183     Fig. 5 – HRTEM of zirconium (IV) tungstate  Fig. 6 – UV of zirconium (IV) tungstate     Fig. 7 – Plot of (DhQ)2 versus hȞ  Fig. 8 – Absorbance versus energy spectrum   A band gap of 4.48 eV for nanocrystalline zirconium tungstate is due to ligand to metal charge transfer transition. The band gap also depends on the zirconia and tungstate content in the sample [12]. Also the energy gap is sensitive to particle size in 1 - 10 nm range for many semiconductors including zirconia and WO3.  In  this  size  range,  a  large  fraction  of  atoms  residing at the surface alters the cluster electronic properties and hence the band  gap  value.  Thus  materials  of  desired  band  gap  can  be  designed  by  changing the stoichiometry of Zr to W and thereby varying the particle size.  3. CONCLUSIONS  Zirconium (IV) tungstate is prepared in the nanoform by chemical coprecipitation method with high purity and homogeneity. XRD confirms the crystalline nature of the material. HRTEM and SEM reveal the spherical nature of the particles. Particle size is found to be < 50 nm from HRTEM. The energy gap determined by Tauc relation is 4.48 eV suggesting that it is a n-type semiconductor suitable for device applications which use metal oxide semiconductor such as gas sensors, UV sensors, etc.       184 S. MANOJ, B. BEENA    REFERENCES 1. Y.D. Wang, Z.X. Chen, Y.F. Li, Z.L. Zhou, and X.H. Wu, Solid State Electron. 45, 639 (2001). 2. K. Huang, Q. Pan, F. Yang, S. Ni and D. He, Physica E 39, 219 (2007).  3. S.M. Kanan, C.P. Tripp, Curr. Opin. Solid St. M. 11, 19 (2007). 4. P.Z. Si, C.J. Choi, E. Bruck, J.C.P. Klaasse, D.Y. Geng, and Z.D. Zhang, Physica B 392, 154 (2007). 5. E.B. Franke, C.L. Trimble, J.S. Hale, M. Schubert, and J.A. Woollam, J. Appl. Phys. 88, 5777 (2000). 6. L.C. Chen and K.C. Ho, Electrochim. Acta 46, 2151 (2001). 7. X. Liu, A. Huang, C. Ding and P.K. Chu, Biomaterials 27, 3904 (2006). 8. K.N. Rao, A. Sridhar, A.F. Lee, S.J. Taveneer, N.A. Young and K. Wilson, Green Chem. 8, 790 (2006). 9. I.K. Ghosh, M.K. Mitra and K.K. Chattopadhyay, Nanotechnology 16, 107 (2005). 10. M.M. Bagheri-Mohagheghi, N. Shahtahmasebi, M.R. Alinejad, A. Youssefi and M. Shokooh- Saremi, Physica B 403, 2431 (2008). 11. J.S.O. Evans, T.A. Mary and T. Voget, Chem. Mater. 8, 2809 (1996). 12. H. Zhu, D. Yang, G. Yu, H. Zhang, and K. Yao, Nanotechnology 17, 2386 (2006). 13. D.G. Barton, S.L. Soled, and E. Iglesia, Top. Catal. 6, 87 (1998). 

Synthesis And Characterization Of Novel Nanocrystalline Zirconium (IV) Tungstate Semiconductor

SocioEconomic Challenges Journal (Sumy State University)

 
 
 
J. Nano- Electron. Phys. 
3 (2011) No1, P.179-184 
 2011 SumDU 
(Sumy State University) 
 
 
179 
PACS numbers: 71.20.Be, 68.37.Og  
 
SYNTHESIS AND CHARACTERIZATION OF NOVEL 
NANOCRYSTALLINE ZIRCONIUM (IV) TUNGSTATE SEMICONDUCTOR  
 
S. Manoj, B. Beena 
 
 Department of Chemistry, D.B. College,  
 Sasthamcotta, Kollam, Kerala, India 690 521 
 E-mail: beenadbc@gmail.com 
 
Nanocrystalline zirconium (IV) tungstate is prepared by chemical coprecipitation 
method using ethylene diamine tetra acetic acid as the templating agent. Elemental 
composition is determined by EDS. The characteristic bonding position is identified 
using FTIR.XRD is used to find the theoritical value of size and phase identification 
using  JCPDS.  Morphology  is  examined  using  SEM and  HRTEM.  UV  absorption  at  
260 nm corresponds to an energy gap of 4.48 eV, characteristic of semiconducting 
nanoparticles.  
 
Keywords: ZIRCONIUM (IV) TUNGSTATE, SEMICONDUCTOR, BAND GAP, EDS, 
HRTEM, ZIRCONIA, TUNGSTEN OXIDE 
 
(Received 04 February 2011, in final form 20 March 2011) 
 
1. INTRODUCTION 
 
Metal oxide semiconductor nanomaterials are usable as semiconducting gas 
sensors  because they have many advantage such as  small  diamensions,  low 
cost, low power consumption, on-line operation and high compatibility with 
microelectronic processing. These include SnO2, WO3, ZrO2, WO3, etc. These 
materials have non-stoichiometric structures, so free electrons orginating 
from oxygen vacancies contribute to electronic conductivity [1]. Tungsten 
oxide  is  an  n-type  semiconductor  with  energy  gap  in  the  range  of   
5.59 - 5.7 eV. Therefore, it is suitable for applications such as 
electrochromic, optochromic and gasochromic coatings for smart windows, 
information display and various sensors [2]. Many researchers have studied 
the sensor, magnetic and electric properties of WO3 prepared by heat 
treatment,  arc  discharge,  sol  gel  etc  with  different  morphology  and  
structure. These materals are studied in different forms such as nanowires, 
nanorods, dopped with transition metal, etc [3, 4, 5, 6] which are either in 
the isolated form or in mixed oxide form. These mixed oxide forms are non-
stoichiometric forms with varying metal concentration. 
 In the present work, nanoform of zirconium (IV) tungstate is prepared in 
the stoichiometric form by chemical coprecipitation method. The material is 
well characterized using EDS, XRD, FTIR, SEM and HRTEM. UV spectrum 
is used to find the optical band gap. 
 
 
 
180 S. MANOJ, B. BEENA  
 
 
2. EXPERIMENTAL  
 
2.1 Preparation of zirconium (IV) tungstate in the nanoform 
 
The  nanoform  of  zirconium  (IV)  tungstate  is  synthesized  by  chemical  
coprecipitation method. In this, equimolar aqueous solutions of zirconium 
oxychloride  and  sodium  tungstate  in  the  volume  ratio  1:2  is  added  to  
ethylene diamine tetra acetic acid template at a pH ~ 1.5 with constant 
stirring using a magnetic stirrer. The precipitate of zirconium (IV) 
tungstate is separated by filtration and washed with distilled water. It is 
then converted to the hydrogen form by immersing in 1M HCl.  
 
2.2 Characterization of the material 
 
EDS spectrum of the material was taken using JOEL Model JED-2300. X-ray 
diffractogram (2ș   10 - 90q)  was  obtained  on  XPERT-PRO  powder  
diffractometer with Cu-KĮ radiation. The FTIR spectrum was recorded using 
KBr wafer on the Thermo Nicolet FTIR model AVATAR 370 DTGS.SEM was 
taken from BJOEL Model JSM-6390LV.PHILIPS Model CM 200 was used to 
take the HRTEM. The absorption spectra were recorded at room temperature 
using SHIMADSU UV-2550 UV Visible spectrophoto-meter. 
 
2.3 Results and Discussion 
 
EDS spectrum shows the presence of zirconium and tungsten in the 
stichiometric proportion. The empirical formula calculated is Zr2W3O13. The 
EDS  spectrum  is  shown  in  figure  1.  The  X-ray  diffractions  of  the  
nanoparticles of zirconium (IV) tungstate consist (figure 2) of cubic phases 
of ZrW2O8, agreeing with the JCPDS file No.89-6670 with small amount of 
isolated cubic zirconia (JCPDS file No.89-9069) and hexagonal tungsten 
oxide (JCPDS file No.82-2459).  
 
 
 
Fig. 1 – EDS of zirconium (IV) tungstate 
 
 
 
 
 SYNTHESIS AND CHARACTERIZATION OF NOVEL… 181 
 
 
 
Fig. 2 – XRD of zirconium (IV) tungstate 
 
 FTIR spectrum (figure 3) shows bands due to water molecules/surface 
hydroxyl groups (~ 3415 cm – 1, 1637 cm – 1, 1380 cm – 1). Band in the region 
837  cm  is  due  to  24WO  species  and  at  711  cm
 – 1 is  due  to  W-O  stretching  
vibration. Band in the region 493 cm – 1 is due to Zr-O vibration [7, 8]. 
 SEM and HRTEM shown in figure 4 and figure 5 are used to examine the 
morphology of the nanomaterial. The spherical nature of the particles is 
revealed from both the SEM and HRTEM. Further from HRTEM it is seen 
that the particles are less than 50 nm in size. 
 UV Spectrum shown in figure 6 gives information about excitonic or 
interband transition of nanocrystalline material. It shows absorption at 
260 nm which corresponds to an energy gap of 4.77 eV. The fundamental 
absorption which corresponds to electron excitation from the valence band to 
the conduction band is used to determine the nature and the value of optical 
band gap. The relation between absoption coefficient (D) and incident photon 
energy (hQ) is given by the Tauc relation, 
 
 (DhQ)1/n   A(hQ – Eg),  
 
where A is  a  constant,  Eg is the band gap of the material, D, is the 
absorption coefficient and the exponent ‘n’ depends on the type of transition 
[9]. The value of band gap can be determined by plotting (DhQ)1/n versus hȞ 
(figure 7) and extrapolating the straight line portion of the graph to hȞ axis. 
The direct allowed band gap calculated is 4.48 eV. A more straight forward 
method of determining an approximate value of band gap regardless of band 
structure is by plotting the absorbance versus energy, and extrapolating to 
zero  absorbance  which  in  this  case  gives  a  band  gap  of  4.49  eV.  Bulk  
ZrW2O8 is an insulating dielectric ceramic and the calculated band gap for 
D-phase is 2.81 eV and for Ȗ-phase is 1.74 eV [10]. The increase in the band 
gap  to  4.48  eV  of  this  material  is  due  to  small  size  and  the  quantum  
confinement limiting. The quantum confinement effect is expected for 
semiconducting nanoparticles and the absorption edge will be shifted to high 
energy with decrease in particle size [11]. 
 
 
 
182 S. MANOJ, B. BEENA  
 
 
 
 
Fig. 3 – FTIR of zirconium (IV) tungstate 
 
 
 
 
Fig. 4 – SEM of zirconium (IV) tungstate 
 
 
 
 SYNTHESIS AND CHARACTERIZATION OF NOVEL… 183 
 
 
 
 
Fig. 5 – HRTEM of zirconium (IV) 
tungstate 
 
Fig. 6 – UV of zirconium (IV) 
tungstate 
 
  
 
Fig. 7 – Plot of (DhQ)2 versus hȞ 
 
Fig. 8 – Absorbance versus energy 
spectrum 
 
 A band gap of 4.48 eV for nanocrystalline zirconium tungstate is due to 
ligand to metal charge transfer transition. The band gap also depends on the 
zirconia and tungstate content in the sample [12]. Also the energy gap is 
sensitive to particle size in 1 - 10 nm range for many semiconductors 
including zirconia and WO3.  In  this  size  range,  a  large  fraction  of  atoms  
residing at the surface alters the cluster electronic properties and hence the 
band  gap  value.  Thus  materials  of  desired  band  gap  can  be  designed  by  
changing the stoichiometry of Zr to W and thereby varying the particle size. 
 
3. CONCLUSIONS 
 
Zirconium (IV) tungstate is prepared in the nanoform by chemical 
coprecipitation method with high purity and homogeneity. XRD confirms 
the crystalline nature of the material. HRTEM and SEM reveal the spherical 
nature of the particles. Particle size is found to be < 50 nm from HRTEM. 
The energy gap determined by Tauc relation is 4.48 eV suggesting that it is 
a n-type semiconductor suitable for device applications which use metal 
oxide semiconductor such as gas sensors, UV sensors, etc.  
  
 
 
 
184 S. MANOJ, B. BEENA  
 
 
REFERENCES 
1. Y.D. Wang, Z.X. Chen, Y.F. Li, Z.L. Zhou, and X.H. Wu, Solid State Electron. 
45, 639 (2001). 
2. K. Huang, Q. Pan, F. Yang, S. Ni and D. He, Physica E 39, 219 (2007).  
3. S.M. Kanan, C.P. Tripp, Curr. Opin. Solid St. M. 11, 19 (2007). 
4. P.Z. Si, C.J. Choi, E. Bruck, J.C.P. Klaasse, D.Y. Geng, and Z.D. Zhang, Physica B 
392, 154 (2007). 
5. E.B. Franke, C.L. Trimble, J.S. Hale, M. Schubert, and J.A. Woollam, J. Appl. Phys. 
88, 5777 (2000). 
6. L.C. Chen and K.C. Ho, Electrochim. Acta 46, 2151 (2001). 
7. X. Liu, A. Huang, C. Ding and P.K. Chu, Biomaterials 27, 3904 (2006). 
8. K.N. Rao, A. Sridhar, A.F. Lee, S.J. Taveneer, N.A. Young and K. Wilson, Green 
Chem. 8, 790 (2006). 
9. I.K. Ghosh, M.K. Mitra and K.K. Chattopadhyay, Nanotechnology 16, 107 (2005). 
10. M.M. Bagheri-Mohagheghi, N. Shahtahmasebi, M.R. Alinejad, A. Youssefi and 
M. Shokooh- Saremi, Physica B 403, 2431 (2008). 
11. J.S.O. Evans, T.A. Mary and T. Voget, Chem. Mater. 8, 2809 (1996). 
12. H. Zhu, D. Yang, G. Yu, H. Zhang, and K. Yao, Nanotechnology 17, 2386 (2006). 
13. D.G. Barton, S.L. Soled, and E. Iglesia, Top. Catal. 6, 87 (1998). 


Synthesis And Characterization Of Novel Nanocrystalline Zirconium (IV) Tungstate Semiconductor

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