Assessment of crystalline phase change and porosity by Rietveld refinement on lightweight cullet and paper ash glass-ceramic

Lightweight glass-ceramic from waste material consists of (x) paper ash- (80-x) cullet – 20 Kaolin clay where (10 ≤ x ≤ 30 weight %) are sintered at 900°C, 1000°C and 1100°C using conventional solid-state reaction technique. The influence of composition and sintering temperature on density, crystalline phase, porosity and surface pore morphology was studied. The crystal symmetry, space group and unit cell dimensions which are executed from XRD data are analyzed using SmartLab Studio II Powder XRD software. Meanwhile, the lattice parameter, cell volume, theoretical densities and porosity were estimated by Rietveld refinement method. The results reveal that all parameters exhibit a temperature-dependent character, as the temperature is increased, the density decreases and porosity increases due to bloating effects. It is also found out that the glass-ceramic compose of 25 paper ash −55 cullet-20 Kaolin clay, sintered at 900°C exhibits an optimum characteristic of the sample density reached optimum because of vitrification between cullet glass, paper ash and kaolin clay to form liquid phase which promotes adhesion and polymerization. It is observed that the surface morphology of the sample is affected by the crystallization process during sintering.