Enhanced dielectric performance of metakaolin-H3PO4 geopolymers

Phosphoric acid based geopolymers are a class of materials that present different properties compared with alkali-based ones. As an example, this kind of geopolymers are characterized by low dielectric properties so that they could be used as encapsulating materials. The objective of this study is to improve dielectric performance of phosphoric acid based geopolymers by reducing dielectric parameters such as dielectric permittivity and electrical conductivity. For this reason, dielectric properties of a geopolymer cured at 7 and 28 days, and then heated at different temperatures were investigated. Results showed a significant decrease in dielectric parameters for a geopolymer aged at 28 days and heated to high temperatures. This decline was attributed mainly to the consumption of free charges provided by phosphoric acid H3PO4 and ionized water. (C) 2015 Elsevier B.V. All rights reserved.