All Solid-State Electrode With Low Contact Resistance and Low Polarization for Measuring the Electrical Properties of Rocks

Accurate measurement of rock electrical properties plays a crucial role in resource exploration and geological exploration. But there are kinds of problems with traditional rock measuring electrodes including high contact resistance, high electrode polarization, low stability and so on. To solve these problems, we designed and fabricated an all solid-state electrode with low contact resistance, low polarizability and high stability. The electrode consists of silver (Ag) and silver chloride (AgCl). To reduce the contact resistance between the electrode and rocks, the electrode was fabricated by powder sintering and repressing, and a scanning electron microscope (SEM) showed that the surface of the electrodes was multi-holes and coarse which is beneficial to reduce contact resistance. In addition, the Ag and AgCl mixture was prepared in the polyvinyl pyrrolidone (PVP) gel, which reduced the particle size of the AgCl and led to a low polarization degree of the electrode. An experimental system for evaluation and characterization was designed to measure the basic characteristics, stability, contact resistance and polarization of the electrodes, which are essential features and will affect the accuracy of electrical measurement. And the copper (Cu) electrode is the reference electrode. The results showed that the maximum resistance of the electrode pair is lower than 0.13 Ω. Through the measurements of core samples with different moisture content, contact resistances are lower than the Cu electrodes by at least 74%, and the accuracy of resistivity measurement is increased by more than 25%. The polarization degree of the electrode is reduced by more than 65%. After multiple measurements, the electrodes still maintain great performance and the uncertainty in measurement keeps at a low level. These characteristics will improve the measuring accuracy of the core electrical properties remarkably. Therefore, this research will promote the study of petrophysical and the exploration of mineral resources.