Effect of doping of divalent and trivalent metal ions on the structural and electrical properties of magnesium aluminate

✍ Scribed by Muhammad Javed Iqbal; Saima Farooq

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 846 KB
• Volume: 136
• Category: Article
• ISSN: 0921-5107
• DOI: 10.1016/j.mseb.2006.09.009

✦ Synopsis

Nanosized magnesium aluminate materials doped by divalent cations (Ca 2+ , Ba 2+ , Sr 2+ ) and trivalent cations (Cr 3+ , Mn 3+ , Fe 3+ ) having nominal compositions Mg 1-x M x Al 2 O 4 and MgAl 2-x M x O 4 (x = 0.02-0.1), respectively, were synthesized by the sol-gel method. The samples were characterized by X-ray diffraction (XRD) and dc electrical resistivity measurements. The XRD data showed that all the samples were spinel single phase cubic closed packed crystalline materials having crystallite sizes between 6 and 35 nm. The lattice constant and X-ray density were found to be affected by the ionic radii of doped metal cations investigated here. Both the bulk density (d b ) and X-ray density (d x ) of doped materials increased whereas the porosity percentage (P) decreased with the increase in the contents of the substituents. The dc-electrical resistivity of all the samples was measured in temperature range 160-400 • C by a two-point probe method and was found to decrease with temperature as expected for semiconductors. It was observed that alkaline earth metal dopants increased the resistivity of MgAl 2 O 4 more than that by transition metal dopants. Arhenius activation energy of hopping of electron for all the samples was also calculated.