Study on the measurement method for resistivity of mineral powder — Taking micro-crystal muscovite for example

There has been no an effective method to measure resistivity of mineral powder and other powder materials until now. According to the national standards GB/T1410-2006, the method to measure resistivity of mineral powder and other powder materials was studied by using the digital high resistance meter and a small measurement electrode which is adequate for the measurement of flat specimen whose diameter is 18 mm. A formula to calculate resistivity of mineral powder by the testing data of its powder compacts was derived according to the compacts characteristics and the generalized effective medium equation (GEM). Then, taking micro-crystal muscovite for example, the experimental results proves that the measurement method is effective and feasible because the resistivity data of mineral powders are the same as that of their dense blocky samples. Further experimental results show that the volume resistivity and surface resistivity of mineral powder are not influenced by mineral particle size. And the upper and lower faces of powder compacts do not affect the volume resistivity of mineral powder, but affect the surface resistivity obviously. So, it is necessary to characterize the surface resistivity of mineral powder by the testing data of the upper face (punch face) of powder compacts. Moreover, the resistivity of mineral powder is greatly influenced by both the drying time and standing time in air. Therefore, in order to obtain correct result, the samples should be dried to constant weight before testing, isolated from air during cooling and measured immediately when exposed to air, and the testing time should be as short as possible.