Size Effects in Zinc-Kaolin Composite Resistors

Zinc-kaolin composite resistors have been produced from naturally occurring materials such as zinc and kaolin. The composite resistors were produced with zinc powder content varying from 0, 20, 50, 70 and 90 %(vol.). Composite rods of dimension 65 mm x 6.5 mm x 3.2 mm were produced in a mould using a compaction method with a constant pressure of about (6.35 ±0.02) x 10⁸ N/m². The rods were subjected to varying annealing temperatures ranging between 300°C and 1000°C for a duration of one hour with an electric furnace in increasing steps of 100°C. Results showed that inverse size effect namely, shorter resistors having higher resistance dominate the zinc-kaolin composite resistance at all filler concentrations considered. Inverse effect is highest in resistors annealed at 600°C and lowest for resistors annealed at 300°C. Observation showed that the magnitude of the inverse size effect is a function of the difference between the channel resistance of the rods and the resistance of its end-terminals.