A Substantial Red and Blue Shift in the Band Gap of Gamma Alumina Through Controlling the OH/Al and Concentration of Sulfate Precursor

Ghamari, M.; Ghasemifard, M.

doi:10.22068/ijmse.17.2.85

Volume 17, Issue 2 (June 2020) IJMSE 2020, 17(2): 27-33 | Back to browse issues page

‎ 10.22068/ijmse.17.2.85

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Ghamari M, Ghasemifard M. A Substantial Red and Blue Shift in the Band Gap of Gamma Alumina Through Controlling the OH/Al and Concentration of Sulfate Precursor. IJMSE 2020; 17 (2) :27-33
URL: http://ijmse.iust.ac.ir/article-1-1478-en.html

A Substantial Red and Blue Shift in the Band Gap of Gamma Alumina Through Controlling the OH/Al and Concentration of Sulfate Precursor

M. Ghamari

, M. Ghasemifard

Abstract: (10506 Views)

In this research, the dependence of the optical band gap of nano gamma alumina on the OH/Al ratio and concentration of aluminum sulfate is measured through diffuse reflectance spectroscopy (DRS) in the range of 900-1100nm. The samples were prepared via sol-gel method. The results showed that the band gap is pH and concentration-dependent but in a different way. The direct band gap of alumina was determined to be 3.40, 4.37, 3.90, and 3.65 eV for samples prepared at pH 6, 7, 8, and 9, respectively. A decreasing trend was observed with increasing pH (except for pH6). The lowering of the band gap may be associated with the variations in particles size during synthesis due to the quantum size effect. The values of the band gap increased significantly through increasing concentration from 3.90 to 5.65 eV for 0.1M to 0.3M. The role of concentration in band gap control is remarkably more than pH.

Keywords: alumina, band gap, concentration, DRS, Tauc relation