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Water-based sol-gel nanocrystalline barium titanate: Controlling the crystal structure and phase transformation by Ba:Ti atomic ratio

Mohammadi, M. R ; Sharif University of Technology | 2009

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  1. Type of Document: Article
  2. DOI: 10.1007/s10853-009-3758-3
  3. Publisher: 2009
  4. Abstract:
  5. Highly stable, water-based barium titanate (BaTiO3) sols were developed by a low cost and straightforward sol-gel process. Nanocrystalline barium titanate thin films and powders with various Ba:Ti atomic ratios were produced from the aqueous sols. The prepared sols had a narrow particle size distribution in the range 21-23 nm and they were stable over 5 months. X-ray diffraction pattern revealed that powders contained mixture of hexagonal- or perovskite-BaTiO3 as well as a trace of Ba2Ti 13O22 and Ba4Ti2O27 phases, depending on annealing temperature and Ba:Ti atomic ratio. Highly pure barium titanate with cubic perovskite structure achieved with Ba:Ti = 50:50 atomic ratio at the high temperature of 800 °C, whereas pure barium titanate with hexagonal structure obtained for the same atomic ratio at the low temperature of 500 °C. Transmission electron microscope revealed that the crystallite size of both hexagonal- and perovskite-BaTiO3 phases reduced with increasing the Ba:Ti atomic ratio, being in the range 2-3 nm. Scanning electron microscope analysis revealed that the average grain size of barium titanate thin films decreased with an increase in the Ba:Ti atomic ratio, being in the range 28-35 nm. Moreover, based on atomic force microscope images, BaTiO3 thin films had a columnar-like morphology with high roughness. One of the highest specific surface area reported in the literature was obtained for annealed powders at 550 °C in the range 257-353 m 2g-1. © 2009 Springer Science+Business Media, LLC
  6. Keywords:
  7. Annealed powders ; Annealing temperatures ; Aqueous sols ; Atomic force microscope images ; Atomic ratio ; Average grain size ; Barium titanate thin films ; Cubic perovskite ; Hexagonal structures ; High temperature ; Low costs ; Low temperatures ; Nanocrystalline barium titanate ; Phase transformation ; Scanning Electron Microscope ; Transmission electron microscope ; Water based ; Atoms ; Barium ; Crystal atomic structure ; Crystallite size ; Diffraction ; Gelation ; Gels ; Holographic interferometry ; Microscopes ; Nanocrystalline powders ; Oxide minerals ; Perovskite ; Powders ; Scanning electron microscopy ; Sol-gel process ; Sol-gels ; Sols ; Thin films ; Transmission electron microscopy ; X ray powder diffraction ; Barium titanate
  8. Source: Journal of Materials Science ; Volume 44, Issue 18 , 2009 , Pages 4959-4968 ; 00222461 (ISSN)
  9. URL: https://link.springer.com/article/10.1007/s10853-009-3758-3