Determination of the band-gap energy of ceramic ZnO doped with MnO by Photopyroelectric technique
Azmi Zakaria, Zahid Rizwan, Mansor Hashim, Abdul Halim Shaari,
W. Mohmood Mat Yunus, Elias Saion.
Department of Physics,
Faculty of Science, Universiti Putra
43400 Serdang, Selangor.
Photopyroelectric spectroscopy (PPES) is used to study the band-gap energy (Eg) of ZnO doped with MnO of 0.1 to 2.0 Mol % and sintered at various isothermal sintering temperature ranged from 850oC to 1300oC. The wavelength of incident light is kept in the range from 300 nm to 800 nm at a modulation frequency of 9 Hz. The photopyroelectric spectrum with reference to the doping level and sintering temperature is discussed. Eg is estimated from the plot vs h and is about 3.0 eV for samples with 850oC sintering temperature at all doping levels. At higher sintering temperatures the value of Eg decreases with the MnO mol %; beyond 1 mol % Eg becomes constant at about 2.0 eV. The x-ray diffractrometry shows that the crystal structure of ZnO doped with different mol % of MnO at all sintering temperatures remains to be of hexagonal type but a small peak is found related to the new phase ZnMn2O4 only at 1050oC sintering temperature at 2 mol % of MnO doping level. Density is decreased from 95.5% to 87% with the increase in sintering temperature and doping level.
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