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

Abstract Phosphoric acid-based geopolymers were synthesized using metakaolin (Al 2 O 3 –2SiO 2 ) and different amounts of phosphoric acid (H 3 PO 4 ) at an ambient temperature. Structural and thermal properties of geopolymers with different molar ratios SiO 2 /H 3 PO 4 (Si/P =1.25, 1.5 and 1.75) were investigated to study the effect of the molar ratio SiO 2 /H 3 PO 4 (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 1–10 6 Hz revealed that the permittivity, the dielectric loss and the electrical conductivity of geopolymers at room temperature were found to be strongly dependent on the H 3 PO 4 concentration. In fact, the addition of phosphoric acid improved the ionic conduction resulting in a great change in the dielectric properties.