Comparison of the morphology and structure of WO₃ nanomaterials synthesized by a sol-gel method followed by calcination or hydrothermal treatment

Abstract

Tungsten (VI) oxide (WO₃) nanomaterials were synthesized by a sol-gel method using WCl₆ and C₂H₅OH as precursors followed by calcination or hydrothermal treatment. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) equipped with energy dispersive X-ray spectroscopy (EDX) were used to characterize the structure and morphology of the materials. There were significant differences between the WO₃ materials that were calcinated and those that were subjected to a hydrothermal process. The XRD results revealed that calcination temperatures of 300°C and 400°C gave hexagonal structures and temperatures of 500°C and 600°C gave monoclinic structures. The SEM images showed that an increase in calcination temperature led to a decrease in the WO₃ powder particle size. The TEM analysis showed that several nanoparticles agglomerated to form bigger clusters. The hydrothermal process produced hexagonal structures for holding times of 12, 16, and 20 h and monoclinic structures for a holding time of 24 h. The SEM results showed transparent rectangular particles which according to the TEM results originated from the aggregation of several nanotubes.

Key words： WO₃ nanomaterial; sol-gel method; calcination; hydrothermal

Acknowledgments

The authors gratefully acknowledge the financial and facility support from the Ministry of Research and Technology, Republic of Indonesia through Applied Research Incentive 2011(No. RT-2011-3832) and Sepuluh Nopember Institute of Technology (ITS)-Surabaya Indonesia through International Collaboration Research Grant 2011(No. 0750.042/I2.7/PM/2011).

References

1 JCPDS Card No. 41–1230

2 Gillet M, Masek K, Gillet E.Structure of tungsten oxide nanoclusters. Surface Science , 2004, 566-568: 383–389

3 Boulova M, Gaskov A, Lucazeau G. Tungsten oxide reactivity versus CH₄, CO and NO₂ molecules studied by Raman spectroscopy. Sensors and Actuators B, Chemical, 2001, 81(1): 99–106

4 Kanan S M, Tripp C P. Synthesis, FTIR studies and sensor properties of WO₃ powders. Current Opinion in Solid State and Materials Science, 2007, 11(1-2): 19–27

5 Liu Z, Miyauchi M, Yamazaki T, Shen Y. Facile synthesis and NO₂ gas sensing of tungsten oxide nanorods assembled microspheres. Sensors and Actuators B, Chemical, 2009, 140(2): 514–519

6 Wang S H, Chou T C, Liu C C. Nano-crystalline tungsten oxide NO₂ sensor. Sensors and Actuators. B, Chemical, 2003, 94(3): 343–351

7 Yan A, Xie C, Zeng D, Cai S, Hu M. Synthesis, formation mechanism and sensing properties of WO₃ hydrate nanowire netted-spheres. Materials Research Bulletin, 2010, 45(10): 1541–1547

8 Su X, Li Y, Jian J, Wang J. In situ etching WO₃ nanoplates: hydrothermal synthesis, photoluminescence and gas sensor properties. Materials Research Bulletin, 2010, 45(12): 1960–1963

9 Deepa M, Singh P, Sharma S N, Agnihotry S A. Effect of humidity on structure and electrochromic properties of sol-gel-derived tungsten oxide films. Solar Energy Materials and Solar Cells, 2006, 90(16): 2665–2682

10 Chang K H, Hu C C, Huang C M, Liu Y L, Chang C I. Microwave-assisted hydrothermal synthesis of crystalline WO₃-WO₃·0.5H₂O mixtures for pseudocapacitors of the asymmetric type. Journal of Power Sources, 2011, 196(4): 2387–2392

11 Sun Y, Murphy C J, Reyes-Gil K R, Reyes-Garcia E A, Thornton J M, Morris N A, Raftery D. Photochemical and structural characterization of carbon-doped WO₃ films prepared via spray pyrolysis. International Journal of Hydrogen Energy, 2009, 34(20): 8476–8484

12 Ozkan E, Lee S H, Liu P, Tracy C E, Tepehan F Z, Pitts J R, Deb S K. Electrochromic and optical properties of mesoporous tungsten oxide films. Solid State Ionics, 2002, 149(1-2): 139–146

13 Su L, Lu Z. All solid-state smart window of electrodeposited WO₃ and TiO₂ particulate film with PTREFG gel electrolyte. Journal of Physics and Chemistry of Solids, 1998, 59(8): 1175–1180

14 Ha J H, Muralidharan P, Kim D K. Hydrothermal synthesis and characterization of self-assembled h-WO₃ nanowires/nanorods using EDTA salts. Journal of Alloys and Compounds, 2009, 475(1-2): 446–451

15 Pyper O, Schollhorn R, Donkers J J T M, Krings L H M. Nanocrystalline structure of WO₃ thin films prepared by the sol-gel technique. Materials Research Bulletin, 1998, 33(7): 1095–1101

16 Yous B, Robin S, Donnadieu A. Chemical vapor deposition of tungsten oxides: a comparative study by XPS, XRD and RHEED. Materials Research Bulletin, 1984, 19(10): 1349–1354

17 Pyun S I, Kim D J, Bae J S. Hydrogen transport through r.f. magnetron sputtered amorphous and crystalline WO₃ films. Journal of Alloys and Compounds, 1996, 244(1-2): 16–22

18 Abdullah S F, Radiman S, Hamid M A A, Ibrahim N B. Effect of calcinations temperature on the surface morphology and crystallinity of tungsten (VI) oxide nanorods prepared using colloidal gas aphrons method. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006, 280: 88–94

19 Hidayat D, Purwanto A, Wang W N, Okuyama K. Preparation of size-controlled tungsten oxide nanoparticles and evaluation of their adsorption performance. Materials Research Bulletin, 2010, 45(2): 165–173

20 Deki S, Beleke A B, Kotani Y, Mizuhata M. Synthesis of tungsten oxide thin film by liquid phase deposition. Materials Chemistry and Physics, 2010, 123(2-3): 614–619

21 Houx N L, Pourroy G, Camerel F, Comet M, Spitzer D. WO₃ nanoparticles in the 5-30 nm range by solvothermal synthesis under microwave or resistive heating. Journal of Physical Chemistry B, 2010, 114(1): 155–161

22 Brinker C J, Scherer G W. Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing. London: Academic Press Inc, 1990, 2: 47–49

23 Chai F, Tan R, Cao F, Zhai F, Wang X, Shao C, Liu Y. Dendritic and tubular tungsten oxide by surface sol-gel mineralisation of cellulosic substance. Materials Letters, 2007, 61(18): 3939–3941

24 Huirache-Acuña R, Paraguay-Delgado F, Albiter M A, Lara-Romero J, Martínez-Sánchez R. Synthesis and characterization of WO₃ nanostructures prepared by an aged-hydrothermal method. Materials Characterization, 2009, 60(9): 932–937

25 JCPDS Card No. 85–2459

26 JCPDS Card No. 83–0950

27 Cullity B D, Stock S R. Elements of X-ray Diffraction. 3rd ed. London: Prentice Hall, 2001, 170

28 Ramana C V, Utsunomiya S, Ewing R C, Julien C M, Becker U. Structural stability and phase transitions in WO₃ thin films. Journal of Physical Chemistry B, 2006, 110(21): 10430–10435

29 Chatten R, Chadwick A V, Rougier A, Lindan P J D. The oxygen vacancy in crystal phases of WO₃. Journal of Physical Chemistry B, 2005, 109(8): 3146–3156

30 Szilágyi I M, Madarász J, Pokol G, Király P. Tárkányi, Saukko S, Mizsei J, Tòth A L, Szabò A, Varga-Josepovits K. Stability and controlled composition of hexagonal WO₃. Chemistry of Materials, 2008, 20(12): 4116–4125