Modification of the physical properties of semiconducting MgAl(2)O(4) by doping with a binary mixture of Co and Zn ions
- Author(s)
- Muhammad Javed Iqbal, Bushra Ismail, Christian Rentenberger, Herbert Ipser
- Abstract
The effects of doping of MgAl(2)O(4) by a binary mixture of Co and Zn ions on the absorbance, electrical resistivity, capacitance, thermal conductivity, heat capacity and thermal diffusivity are reported in this paper. The materials with the nominal composition Mg(1-2x)(Co,Zn)(x)Al(2)O(4) (x = 0.0-0.5) are synthesized by solution combustion synthesis assisted by microwave irradiation. The substituted spinels are produced with a Scherrer crystallite size of 18-23 nm, as opposed to 45 nm for undoped samples, indicated by X-ray diffraction and confirmed by transmission electron microscopy. These materials also show better thermal stability in the temperature range of 298-1773 K. Three strong absorption bands at 536, 577 and 630 nm are observed for the doped samples which are attributed to the three spin allowed ((4)A(2) (F) -> (4)T(1) (P)) electronic transitions of Co(2+) at tetrahedral lattice sites while pure magnesium aluminate remains transparent in the whole spectral range. The semiconducting behavior of the materials is evident from the temperature dependence of the electrical resistivity. Resistivity and activation energy are higher for the substituted samples. Fitting of the resistivity data is achieved according to the hopping polaron model of solids. Both dielectric constant and loss increase on account of doping. The dielectric data are explained on the basis of space charge polarization. The thermal conductivity and diffusivity are lowered and the heat capacity is increased in the doped materials. Wiedemann-Franz's law is used to compute the electronic and lattice contributions towards the total thermal conductivity.
- Organisation(s)
- Physics of Nanostructured Materials, Department of Functional Materials and Catalysis
- External organisation(s)
- Quaid-i-Azam University
- Journal
- Materials Research Bulletin
- Volume
- 46
- Pages
- 2271-2277
- No. of pages
- 7
- ISSN
- 0025-5408
- DOI
- https://doi.org/10.1016/j.materresbull.2011.08.061
- Publication date
- 2011
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 104003 Inorganic chemistry, 104011 Materials chemistry
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/7d540e8f-8af2-4879-bfe4-5b0667e7fcbb