Structural, thermal and dielectric properties of phosphoric acid-based geopolymers with different amounts of H_3PO_4

摘要

Phosphoric acid-based geopolymers were synthesized using metakaolin (Al_2O_3-2SiO_2) and different amounts of phosphoric acid (H_3PO_4) at an ambient temperature. Structural and thermal properties of geopolymers with different molar ratios SiO_2/H_3PO_4 (Si/P = 1.25, 1.5 and 1.75) were investigated to study the effect of the molar ratio SiO_2/H_3PO_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_3PO_4 concentration. In fact, the addition of phosphoric acid improved the ionic conduction resulting in a great change in the dielectric properties.