Structural, thermal and dielectric properties of phosphoric acid-based geopolymers with different amounts of H3PO4

Abstract

Phosphoric acid-based geopolymers were synthesized using metakaolin (Al2O3–2SiO2) and different amounts of phosphoric acid (H3PO4) at an ambient temperature. Structural and thermal properties of geopolymers with different molar ratios SiO2/H3PO4 (Si/P =1.25, 1.5 and 1.75) were investigated to study the effect of the molar ratio SiO2/H3PO4 (Si/P=1.25, 1.5 and 1.75). The results showed that an increase in the amount of phosphoric acid leads to an augment in the amorphous nature of samples and to a change in their thermal behaviors. Dielectric measurements at a range frequency of 1–106Hz revealed that the permittivity, the dielectric loss and the electrical conductivity of geopolymers at room temperature were found to be strongly dependent on the H3PO4 concentration. In fact, the addition of phosphoric acid improved the ionic conduction resulting in a great change in the dielectric properties.