A new microwave cavity resonator for determining molecular orientation and dielectric anisotropy of sheet materials

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Abstract
A new type of microwave instrument is developed for quick determination of the molecular orientation and dielectric anisotropy in sheet materials. Its cavity resonator differs from the conventional one in that the waveguide is separated by a narrow gap. Thus, it consists of a pair of rectangular waveguides, each partitioned by an iris plate. A given sheet is inserted into the gap, and can be rotated around the axis normal to its plane. The iris diameter and gap width are determined so as to meet the requirement that the transmitted microwave power and the Q value may not drop markedly after insertion of thick films into the gap. Polarized microwaves are irradiated perpendicularly to the sheet, and the transmitted wave intensity is measured at every 1° of rotation angle as the sheet is rotated at a speed of 6.0 s per turn. This operation quickly gives information related to the molecular orientation in the given sample. Dielectric measurements can be made at any rotation angles, allowing the angular dependence of the real and imaginary parts of the complex dielectric constant and, thus, the dielectric anisotropy of the sheet to be determined in a few minutes.

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