The electrical and luminescent properties of a series of ZnO pellets doped with 0.1% Mn, sintered at 1100, 1200, 1300 and 1400 degreesC and furnace cooled have been studied. The impedance spectra of the pellets can result from a grain boundary capacitance. The conductivity of the material increases with increasing sintering temperature. The electrical properties agree with the brick layer-grain boundary model put forward for ZnO-based varistors. All the pellets are photoluminescent with both an identical photoluminescence spectrum and an identical photoluminescence yield. Unlike the pellets sintered at 1100, 1200 and 1400 degreesC, the pellet sintered at 1300 degreesC is electroluminescent. This electroluminescence, which is observed at a voltage lower than the breakdown voltage, evidences the presence of field inhomogeneities and hot electrons inside the pellet. (C) 2004 Elsevier B.V. All rights reserved.