Study of second-phases in Ba(Mg_1/3Ta_2/3) O₃ materials by microwave near-field microscopy

A three-dimensional (3D) finite element simulation was performed to model the behavior of the measuring resonator in an evanescent microwave probe (EMP). A calibration curve was derived using the frequency shift data as standards. The EMP measuring techniques was applied to measure the dielectric properties of Ba(Mg_1/3 Ta_2/3)O₃, BMT, materials. The average dielectric constants for these BMT materials (ε _r=26-30) are consistent with the dielectric properties measured by conventional cavity method. The EMP mapping indicates clearly the presence of higher or lower dielectric constant inclusions in the one-step processed BMT materials, which contain a large proportion of secondary phases. The measurements demonstrate that the EMP method is capable of mapping the distribution of dielectric constant at very high spatial resolution.