Kinetics of Formation and Crystal Structure Determination of Sr₄Al₆O₁₂SO₄

The sulphoaluminate of strontium, Sr₄Al₆O₁₂SO₄, was synthesized by solid state reaction from mixture of SrCO₃, Al₂O₃ and SrSO₄ (3:3:1 molar ratio) as pellets. The kinetics of formation has been studied in the range of temperature between 850ºC and 1100ºC using quantitative X-ray powder diffraction data (XRD) analysis. Likewise, at room temperature, the crystal structure was determined from conventional X-ray powder diffraction data using direct methods and it was refined by the Rietveld method. The kinetics mechanisms that showed the best fit, were identified as geometrical contraction at grain boundary (R_1.1) and nucleation and growing by energy law (P_1.1). The activation energy values obtained were 145.47KJmol^-1 (R_1.1) and 151.35KJmol^-1 (P_1.1), respectively. The resulting crystal structure was orthorhombic type (a: 13.32802Å, b: 13.34430Å and c: 9.38704Å). The observed adjustment parameters were R_B: 0.0985, R_wp: 0.137, R_p: 0.0925 and Chi²: 1.94.

Keywords:
Solid state reaction; Kinetic study; Crystal structure; Rietveld method