Abstract
Defect simulation procedures have been carried out in doped MgAl2O4 spinels. Intrinsic defects which originate from cation antisite disorder, due to the partial interchange of the positions of the divalent and trivalent cations have been studied. It was found that the probability of AI3+ replacing Mg2+ is higher than the inverse process. The results of the simulation studies indicate that the configuration energy is lower for AI3+ being replaced by trivalent impurities (Cr3+, Mn3+ and Co3+) than for the replacement of AI3+ and Mg2+ by divalent impurities (Cr2+, Mn2+ and Co2+) compromising the existence of impurity-vacancy dipoles. Thermally stimulated depolarisation currents (TSDC) spectra of MgAl2O4 spinels show four bands at 120, 160, 250 and 300 K. The presence of these four bands varies from sample to sample. Several crystals simply do not show anyone of these bands. The 160 and 250 K bands are probably of dipolar origin and γ-irradiation up to 1.5 kGy enhances the 250 K peak in the samples that already show this peak and creates the 250 K peak in the samples that did not present it before irradiation.
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