Abstract
The effect of exposure to HCOOH and CH3COOH vapours on the dielectric behaviour of hot pressed AlN ceramic having different volume percentages of porosity is studied. Dielectric constant and dissipation factor both increase after exposure to acid vapours at humidity levels greater than atmospheric. The results indicate that the porosity plays an important role in the change of dielectric parameters on exposure to acid vapours. The exposure effects are found to be completely reversible as, after annealing, the exposed samples show behaviour similar to that of unexposed samples. The results are explained in terms of ionic conduction due to dissociation of these vapours in the presence of moisture.
MST/1137
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