Solid State Science and Technology, Vol. 15, No 2 (2007) 34-43
PHOTOTHERMAL STUDY OF ZnO CERAMIC DOPED WITH TiO2
A. Zakaria, Z. Rizwan, S.A. Halim,
W.M.M. Yunus, M. Hashim
Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
Photopyroelectric spectroscopy (PPES) is a useful tool for examining non-radiative de-excitation in semiconductor materials. The ceramic (ZnO-x, x = 0.4 - 2.7 mol % of TiO2) was sintered at isothermal temperature, 1270 for 1, and 2 hours to investigate its optical properties. The PPES is used to study the energy band gap of this ZnO system with reference to TiOCo2 doping level. The energy band-gap obtained from photopyroelectric spectrum is about constant at 2.82 eV for the samples sintered for 2 hour at all TiO2 doping levels except at 0.4 mol % which is 2.78 eV. The energy band gap decreases with the decrease of sintering time from 2 to 1 hour at all doping levels and is about constant at 2.79 eV for the sintering time of 1 hour except that at 0.6 mol % level which is 2.84 eV. The steepness factors σA and σB which characterize the slop of exponential optical absorption are discussed with reference to the TiO2 doping level. The X-ray diffractrometry shows that the crystal structure of ZnO doped with different TiO2 mol% remains to be of hexagonal type. Microstructure and compositional analysis of the selected areas are analyzed using SEM and EDAX. The maximum relative density 95.16 % is obtained for the ceramic. The grain size is about constant at 26.8 – 311.6 μm up to 1 mol % of TiO2 and then decreases with the increase of TiO2 mol % indicating the excess TiO2 suppresses the grain growth.
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