Variation of temperature dependence of electrical resistivity with crystal structure of artificial graphite products

Electrical resistivity of 12 artificial graphite products was measured by 4-pin probe constant current method in argon atmosphere in a furnace, in the temperature range from ambient to 1200 °C. In order to study the effects of crystal structure of the graphite products on their electric properties, X-ray diffraction (XRD) structural parameters, such as, average interlayer spacing (d002), crystallite sizes (Lc and La) and graphitization degree (P1), were measured by the methodology as outlined in JIS R7651. For the temperature dependence of resistivity of these products, it was observed that the minimum resistivity was located at the temperature ranges from 450 to 700 °C. From the relationship between the temperature dependence of resistivity and XRD structural parameters of the graphite products, some control factors of electrical properties at high temperature was discussed. Between the electrical resistivity at ambient temperature and P1, a mutual relationship could be observed. It was seen that the normalized value of the minimum from the ambient resistivity was related with d002. The temperature showing the minimum resistivity was lowered with enlargement of crystallite size along the a-axis, La. The slope of temperature dependence of resistivity at 1000 °C showed a correlation with La.