On the structural and electrical properties of MgFe(2)O(4), MgMn(0.2)Fe(1.8)O(4), and Mn(3)O(4)

Charge carrier transport via donor/acceptor pairs of similar elements is dominant in n-type MgFe(2)O(4) and p-type Mn(3)O(4) spinels. The temperature-independent activation energy in the form of the nearest neighbor hopping model is applied for Fe(2+)/Fe(3+) pairs of cubic MgFe(2)O(4) spinel in the temperature range of 423–523 K (150–250 °C). At such high temperatures, even for this relatively narrow temperature range, the constant energy barrier deviates to a variable range hopping energy barrier in the case of Mn(3)O(4), due to Jahn-Teller active octahedral sites. Replacing 10 mol% of Fe at octahedral sites with Mn has significantly increased the electron hopping energy barrier and electrical conductivity of MgFe(2)O(4), while keeping the nearest neighbor hopping model dominant. The observed high energy barrier is due to donor/acceptor pairs of different elements (Mn/Fe). Due to a lack of structural distortion, deviation from the nearest neighbor hopping mechanism with temperature-independent activation energy was not observed. Rietveld refined XRD patterns and FT-IR spectra are utilized to support the argument on electrical conductivity mechanisms.