Electrical and Crystallographic Studies of the System CuxNi1-xMn2O4

Electrical and crystallographic properties of the system Cu x Ni 1- x Mn 2 O 4 have been studied. The negative deviation of lattice parameters from Vegard's linearity rule indicates that CuMn 2 O 4 is a normal cubic spinel. The electrical resistivity temperature-behaviour obeys the relation \(ρ{=}ρ₀exp{·}(+ E/kT)\), and the value of activation energy ( Δ E ) for conduction in NiMn 2 O 4 remains constant even after addition of 50 mole percent CuMn 2 O 4 . The thermoelectric power of NiMn 2 O 4 changes sign from negative to positive by an addition of 20 mole percent CuMn 2 O 4 . It is concluded that in CuMn 2 O 4 the Cu is present predominantly in Cu 2+ valence state along with a small number of Cu 1+ ions at tetrahedral sites. The electrical conduction in this system seems to take place through hopping of charge carriers between Mn 3+ and Mn 4+ ions at octahedral sites. A contribution to electrical conduction from tetrahedrally located Cu 2+ and Cu 1+ ions has also been considered.