A.A.Hanna
,
M.Sh.Khalil
,
H.I.Saleh
,
A.F.Ali
材料科学技术（英文）
A series of chemical compositions based on Cr, Fe and O with Zn as a partially substituting ion has been prepared in the general formula ZnxCr1-xFe2O by coprecipitation method using NH4OH as the precipitating agent at pH=10.3. The prepared samples were identified by both thermal analysis (DTA and TGA) and X-ray diffraction (XRD). It was found that no single phase was obtained for any of the studied compositions but a mixture of different phases was observed, depending on the molar percentage of zinc ion substitution as well as on the sintering temperature. The temperature dependence of the electrical conductivity, σ, of the prepared samples was plotted between 25 and 680℃. It was observed that the electrical conductivity increased with temperature for both samples with x=0.00 and 0.80 Zn ion content while it was nearly temperature independent for samples with intermediate Zn concentration x=0.2 and 0.5 mol fraction. The activation energy, Ea, calculated from the linear relation, lgσ-1000/T for the final mixtures (sintered at 1300℃) was calculated.
关键词:
F.F.Hammad
,
M.Sh.Khalil
,
A. H. Salama
材料科学技术（英文）
The electrical conductivity of pure CaTiO3 and that containing 0.5 similar to5.0 mole fraction CuO as dopant were measured in the temperature range 291 similar to 773 K. The conductivity values varied as a function of temperature and dopant concentration. The activation energy in the lower temperature range depended on the impurity content while in the high temperature range it indicated a value of energy gap width. The infrared absorption spectra in the range of 100 similar to 4000 cm(-1) revealed the presence of two main bands at 340 and 570 cm(-1) which were assigned to TiO6 octahedral normal mode. Bands in the range of 106 similar to 270 cm(-1) were due to the vibration of anion TiO3-2. Some bands were observed at higher values due to the presence of lattice imperfections. There was a slight shift in band position with increasing dopant concentration which favors the formation of orthorhombic modification.
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