@article{jmpc2021914,
author={{Muvaka, Patrick and Mugo, Waweru and Ongeri, Richard and Ngaruiya, Mbiyu},
title={Thermochromic Properties of VO<SUB>2</SUB> Thin Films Derived from Thermal Reduction of Sol-Gel Deposited V<SUB>2</SUB>O<SUB>5</SUB>},
journal={Journal of Materials Physics and Chemistry},
volume={9},
number={1},
pages={20--25},
year={2021},
url={http://pubs.sciepub.com/jmpc/9/1/4},
issn={2333-4444},
abstract={Vanadium dioxide (VO<SUB>2</SUB>) thin films were prepared by thermal reduction of vanadium pentoxide (V<SUB>2</SUB>O<SUB>5</SUB>) films and thermochromic properties of the films were investigated. V<SUB>2</SUB>O<SUB>5</SUB> films were prepared by dip-coating glass substrates at different withdrawal speeds of 5, 10, 15, and 20 mm/min. The as-deposited V<SUB>2</SUB>O<SUB>5</SUB> films were annealed at different temperatures of 450, 500, 550 and 600ˇăC in an inert environment of flowing argon gas under normal atmospheric pressure. The as-deposited V<SUB>2</SUB>O<SUB>5</SUB> films were gray in color and the films changed color to golden yellow after annealing. UV-VIS-NIR spectrophotometry and sheet resistance probe were used to evaluate performance of the films. The result shows that a withdrawal speed of 5mm/min and annealing temperature of 500ˇăC produced homogeneous VO<SUB>2</SUB> films with luminous transmittance close to the desired transmittance threshold for day-lighting. This was attributed to reduced thickness and crystallization resulting to low absorption by VO<SUB>2</SUB>. Results showed that 500ˇăC was threshold for obtaining crystalline VO<SUB>2</SUB> films. UV-VIS-NIR analysis revealed solar modulation ability of 5.2%, large transmittance change of over 35ˇăC in the IR region and hysteresis loop of 6.0ˇăC when going through phase transition between 25ˇăC and 90ˇăC. Temperature dependence of sheet resistance revealed semiconductor to metal transition behavior change of 2 orders of magnitude across transition temperature. The film showed semiconductor to metal transition temperature of 61.2ˇăC lower than the classical value of 68ˇăC and was attributed to crystalline structure of the films. This simple solution process followed by thermal reduction makes the VO<SUB>2</SUB> potentially useful in smart window application.},
doi={10.12691/jmpc-9-1-4}
publisher={Science and Education Publishing}
}