SEMICONDUCTING MATERIALS. PART III. AN INVESTIGATION OF THE DIELECTRIC PROPERTIES OF SINGLE-CRYSTAL VERSUS POLYCRYSTALLINE MATERIALS.
STATE UNIV OF NEW YORK ALFRED COLL OF CERAMICS
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Studies were conducted to determine the effect of grain boundaries upon polycrystalline ceramic dielectrics. For this purpose, dielectric measurements of polycrystalline samples were compared with measurements on single crystals. An attempt was made to analyze the results using Koops approach which satisfies the case of a stratified dielectric. However, this approach is shown to be invalid for the samples studied as might be suspected since the assumptions by Koops are not necessarily satisfied. The dielectric properties of MgO single crystals and polycrystalline samples, MgF2 polycrystalline samples and a ZnS sample are presented in graphic form. Activation energies are given for the loss mechanisms present. The effect of adsorbed moisture or gas on improperly prepared samples is demonstrated by comparing dielectric measurements with infrared transmission studies. It is concluded that the increased dielectric constant and dielectric loss in polycrystalline samples is due to a combination of conduction, probably ionic, and interfacial polarization with no unique relaxation time existing. Author