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Particle size, morphology and phase transitions in hydrothermally produced VO2(D).
- Source :
- New Journal of Chemistry; 9/7/2017, Vol. 41 Issue 17, p9216-9222, 7p
- Publication Year :
- 2017
-
Abstract
- Different morphologies and sizes of VO<subscript>2</subscript>(D) particles were synthesised via hydrothermal synthesis using ammonium metavanadate (NH<subscript>4</subscript>VO<subscript>3</subscript>) or vanadium pentoxide (V<subscript>2</subscript>O<subscript>5</subscript>) as a vanadium precursor. By adjusting the concentration of vanadium precursors and the pH of the starting solution, a variety of morphologies and sizes of VO<subscript>2</subscript>(D) particles from 20 nm to 3 μm could be produced. A flower-shape morphology was obtained under strongly acidic conditions, passing through star-shape particles of 1 μm at pH 2.5 and finally obtaining homogeneous round balls of around 3 μm at pH 6.9. Nanoparticles were produced hydrothermally using V<subscript>2</subscript>O<subscript>5</subscript> as a precursor and hydrazine as a reducing agent. The transition from VO<subscript>2</subscript>(D) to thermochromic VO<subscript>2</subscript>(R) in micron scale particles occurred at 350 °C under vacuum. However, the nanoparticles of VO<subscript>2</subscript>(D) had a significantly lower VO<subscript>2</subscript>(D) to thermochromic VO<subscript>2</subscript>(R) transition temperature of 165 °C after annealing for only a few minutes. This is, to our knowledge, the lowest annealing temperature and time reported in the literature in order to obtain a thermochromic VO<subscript>2</subscript> material via another VO<subscript>2</subscript> phase. After the conversion of VO<subscript>2</subscript>(D) microparticles to thermochromic VO<subscript>2</subscript>(R), the metal to insulator transition temperature is 61 ± 1 °C for the heating cycle and 53 ± 1 °C for the cooling cycle. However, VO<subscript>2</subscript>(R) nanoparticles showed a significantly reduced metal insulator transition temperature of 59 ± 1 °C and 42 ± 1 °C for the cooling cycle lower than that reported in the literature for bulk VO<subscript>2</subscript>. This is important due to the need for having a compound with a switching temperature closer to room temperature to be used in smart window devices for energy consumption. W-VO<subscript>2</subscript>(D) star shape microparticle samples were prepared using 2–7 at% of the dopant (using ammonium metavanadate as a precursor), although unexpectedly this does not seem to be a viable route to a reduced metal to insulator transition in this system. [ABSTRACT FROM AUTHOR]
- Subjects :
- HYDROTHERMAL synthesis
PARTICLES
AMMONIUM
Subjects
Details
- Language :
- English
- ISSN :
- 11440546
- Volume :
- 41
- Issue :
- 17
- Database :
- Complementary Index
- Journal :
- New Journal of Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 126779485
- Full Text :
- https://doi.org/10.1039/c7nj02165h