PREPARATION, SINTERING AND ELECTRICAL BEHAVIOR OF COBALT, NICKEL AND ZINC GERMANATE

Cobalt, nickel and zinc germanate were prepared by solid state reactio ns between the relevant oxides in air. Ceramics with monophase structu res could be obtained by adopting the optimum temperature and time. Th e as-fired ceramics exhibited insulating properties; however, by an ad ditional heat treatment under reducing conditions, variable electrical conductivity could be induced in the ceramic bodies. Temperature/resi stivity characteristics of these materials showed typical semiconducti ng behaviour. X-ray studies showed that despite the changes in electri cal behaviour, and apparent changes in colour after annealing, the str uctures remained unaltered. Microstructural studies using scanning ele ctron microscopy also showed that there were no substantial changes du e to the reductive annealing processes.