Microwave Dielectric Mechanism Studied by Microwave Near-Field Microscopy and Raman Spectroscopy

Abstract

Microwave dielectric ceramics such as Ba(Mg 1/3 Ta 2/3 )O 3 and Ba 2 Ti 9 O 20 possess high dielectric constant and low dielectric loss in microwave frequency regime and have tremendous potential for device applications. In these materials, the presence of extrinsic defects, such as secondary phases, usually altered the microwave dielectric properties of the materials markedly, but the correlation of the microwave dielectric response of the materials with their microstructure has not been fully understood due to the lack of dielectric response in the local area. In this article, microwave near-field microscopy and Raman spectroscopy were used to investigate the microwave dielectric mechanism, viz. we measured the microwave dielectric properties of the materials in micron region by using a evanescent microwave probe (EMP) and, at the same time, examined the lattice vibration characteristics of the region by using a micro-Raman spectrum. How the presence of the secondary phase affects the microwave dielectric properties of the materials is thus systematically investigated. The causes of intrinsic or extrinsic dielectric loss were explored by comparing the dielectric images in SEMP at microwave frequencies and the corresponding Raman Spectra.

Improvement on the characteristic of Ba2Ti9O20 microwave dielectric materials prepared by modified co-precipitation method

“…It is known that sharper lattice vibration modes for the materials usually lead to higher (Q × f)-value. 15,16 Meanwhile, the inferior lattice vibration characteristics for the air-sintered samples can be ascribed to the incompletely developed grains for the materials, which is implied by the roundish-rod geometry of the grains in these materials.…”

Milling effect on the microwave properties of Ba2Ti9O20 investigated by EMP technique

“…The effect of SiO 2 -contamination induced in the milling process is investigated. Moreover, to directly examine the connection between the dielectric properties and the microstructure of Ba 2 Ti 9 O 20 ceramics, we use the evanescent microwave probe (EMP) technique [7][8][9] to locally image the microwave response.…”