Structural and electrical properties of geopolymer materials based on different precursors (kaolin, bentonite and diatomite)

Abstract

Geopolymers (GP) were successfully synthesized from metabentonite (MB), metadiatomite (MD) and metakaolinite (MK). Characterization of their phase structure and microstructure was performed by XRD, FTIR, SEM/EDX methods. A SEM micrograph of GPMD shows a homogeneous surface with some longitudinal cavities in the gel, and it is significantly different from the micrographs of the other two geopolymer samples, GPMB and GPMK. A considerable amount of unreacted particles, as well as the presence of pores in the geopolymer matrix of GPMK and GPMD, indicate an incomplete reaction in the system. Aluminosilicate inorganic polymers, geopolymers, are quasi solid electrolytes which possess a high electrical conductivity at room temperature in relation to materials of similar chemical composition. The highest conductivity was found for the sample obtained from GPMK, amounting to 2.14 × 10–2 Ω–1cm–1at 700 ºC. The corresponding activation energies of conductivity for this sample amounted to 0.33 eV in the temperature range of 500–700 ºC. The geopolymer synthesized from metakaolin has good ionic conductivity values, which recommends it for use as an alternative material for an SOFC (Solid Oxide Fuel Cell).