Sintering behaviour of magnetite (Fe₃O₄) under magnetic field heating of 2.45 GHz microwave

The wavelength is much larger than the dimensions of heated objects in GHz range. It suggests that vectors of magnetic or electric field are equal all over in atomic, molecules and crystal in the materials. As the photon energy is very low, the energy carried by each cycle of the wave is only a few Gauss in the wave propagating with 100 watts/cm³ at 2.45 GHz. The two characters of field uniformity and low energy in the wave vectors suggest that small collective electron motions generate coupled with the wave. If the ordered motions were scattered by some mechanism, the collective (kinetic) motions of electrons would dissipate and accumulate into the materials. On the other, the sintering materials become un-uniformity like uneven crystal orientation and/or heterogeneous as multicomponent. Therefore, each powder in sintering materials has different sensitivity for the collective motions of microwave. For inspecting the interaction between collective motion and un-uniform materials, the Fe₃O₄ were heated by magnetic field of microwave and by conventional heating. As results, sintered sample heated by magnetic field was observed the local abnormal grain growth.