Microstructural development of tin-doped ZnO bulk ceramics

The recent interest in room temperature ferromagnetic semiconductors has led to an intense research in ZnO-based ceramics doped with different magnetic elements such as Mn, Co, Ni, etc. An improvement of the semiconductor behaviour of ZnO is also necessary to obtain good electrical properties and in this way tin oxide is expected to increase the electrical conductivity of bulk ZnO, as it is assumed to act as a doubly ionized donor. However, the range of solid solution of tin into ZnO lattice is found to be limited as it rapidly segregates to form secondary phases. Concentrations as low as 0.1 mol% of SnO2 lead to the formation of a spinel-type phase whose presence yields a non-linear electrical response that hinders the donor effect of tin oxide.