Tuning of crystal phase structure in hydrated WO₃ nanoparticles under wet chemical conditions and studies on their photochromic properties

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• 作者：Sandhya Songara ; Vatsana Gupta ; Manoj Kumar Patra ; Jitendra Singh ; Lokesh Saini ; Genekehal Siddaramana Gowd ; Sampat Raj Vadera ; Narendra Kumar ; ^{nkjainjd@yahoo.com}
• 关键词：A. Oxides ; B. Chemical synthesis ; C. X-ray diffraction ; D. Crystal structure ; D. Optical properties
• 刊名：Journal of Physics and Chemistry of Solids
• 出版年：2012
• 出版时间：July, 2012
• 年：2012
• 卷：73
• 期：7
• 页码：851-857
• 全文大小：739 K

文摘

Hydrated tungsten oxide nanoparticles have been synthesized using a simple wet chemical method while varying the concentration of HCl. XRD studies show that the variation in HCl concentration from 1 M to 6 M in the reaction results into gradual change in crystal structure of hydrated WO₃ from hexagonal (WO₃¡¤0.33H₂O) to pure orthorhombic (WO₃¡¤H₂O), through a series of samples with mixed phase of the two indifferent ratios. The similar variations in the degree of hydration and phase variations have also been observed from Raman, FTIR and TGA studies. The average crystallite size of the hydrated WO₃ particles was estimated to be ?6 nm from XRD line broadening and AFM studies showed the formation of spherical shaped particles for all the samples. The photochromic studies were carried out on the composite films of these materials in the polymeric matrix of polyvinyl alcohol (PVA) while exposing to UV light. The composite films show interesting variations in the photochromic behavior depending on the crystal structure of hydrated WO₃ filler. The photochromic behavior has been explained on the basis of EPR spectra of hydrated WO₃.