Sintering and deformation properties of forsterite + diopside aggregates in an electrical field

Abstract

A new technique called “flash sintering” has been proposed in the field of materials science. When a compact powder of oxide material is sintered in an electrical field, densification accelerates at a certain temperature, and the sintering is completed in a shorter time at a lower temperature as compared with conventional sintering experiments. In addition, tensile deformation experiments conducted on a dense oxide body in an electrical field have shown that plastic deformation can be enhanced at lower temperatures with lower stresses, as compared with conventional deformation experiments. Fluctuations in the magnetic and electrical fields derived from outside Earth, such as solar activity, induce an electrical field inside Earth. The strength of the electrical field in Earth's mantle is still debated, but it could be up to 10−6 V/cm. Although electrical fields inside Earth may affect the deformation behavior of rocks, no experimental studies have been conducted on geomaterials to assess this effect. Therefore, based on these recent findings in materials science, we conducted sintering and deformation experiments to examine the effects of an electrical field on high-temperature mass transport. We used forsterite + diopside crystal aggregates, which are good analogs for Earth's mantle. The sintering experiments demonstrated that the relative density increases with an increasing electrical field at a constant temperature. In the deformation experiment with a constant displacement rate, the samples in an electrical field of 1000 V/cm were deformed by 4.4× lower stress than for samples not in an electrical field. These features suggest that diffusional mass transport is enhanced in an electrical field. We propose that the presence of an electrical field within Earth may accelerate the deformation of mantle materials.