Kinetics of Formation and Crystal Structure Determination of Sr4Al6O12SO4

José Amparo Rodríguez,Jesús Torres,Enrique Rocha Rangel,Estrella Guadalupe Ríos Rodríguez,José Manuel Almanza Robles,Elizabeth Refugio García

doi:10.1590/1980-5373-mr-2016-0639

Abstract

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 (R1.1) and nucleation and growing by energy law (P1.1). The activation energy values obtained were 145.47KJmol-1 (R1.1) and 151.35KJmol-1 (P1.1), respectively. The resulting crystal structure was orthorhombic type (a: 13.32802A, b: 13.34430A and c: 9.38704A). The observed adjustment parameters were RB: 0.0985, Rwp: 0.137, Rp: 0.0925 and Chi2: 1.94.

Highlights

Reactions between solids are diverse, determinants being i) the thermodynamic conditions, ii) structural conditions and iii) reaction mechanisms governing the process
Due to the above and knowing that the information about the compounds formed within the system SrO–Al2O3–SrSO4 is low[6,7,8,9,10] as an integral part of the synthesis and characterization of strontium sulfoaluminate, Sr4Al6O12SO4, this paper presents i) the kinetic study of the formation from quantitative data best fit against kinetic models by solid state reaction and ii)
The research was conducted in three stages; in the first stage the preparation and characterization of the samples are presented, in the second stage a study was performed to establish the kinetic of formation of Sr4Al6O12SO4 in the SrO–Al2O3–SrSO4 system and the third stage the crystal structure of the same strontium compound was determined

Summary

Introduction

Reactions between solids are diverse, determinants being i) the thermodynamic conditions, ii) structural conditions and iii) reaction mechanisms governing the process. The Knowledge of the kinetic mechanisms that characterize a solid state reaction is essential for the control of a process, critical issue in the development of new products[1]. Knowledge of the crystal structure of any material is a fundamental requirement to understand and control the properties[2]. In recent decades they have seen a considerable increase in the development of the structure determination from powder diffraction data[3,4,5]. Due to the above and knowing that the information about the compounds formed within the system SrO–Al2O3–SrSO4 is low (only synthesis at high temperature, some physical and chemical properties of Sr4Al6O12SO4 were reported)[6,7,8,9,10] as an integral part of the synthesis and characterization of strontium sulfoaluminate, Sr4Al6O12SO4, this paper presents i) the kinetic study of the formation from quantitative data best fit against kinetic models by solid state reaction and ii)

Experimental Procedure

Preparation and characterization of samples

Kinetic study

Crystalline structure determination

Crystal structure

Conclusions