Evaluation of Non Crystalline Phase in AZS Refractories by XRD Methods

Abstract

The relation between the atomic structure and the macroscopic properties and behaviors of a material constitute one of the objectives of the materials science, particularly in the design and development of ceramic materials.Crystalline and non crystalline phases together with pores, grain boundaries, etc. affect mechanical and fracture properties as well as chemical resistance and electric properties. These aspects will be bonded to the raw materials chosen and the whole processing route.In glass industry, although there are other electrofused refractories such as the alumina ones used in the feeding of the fusion kilns, probably the most used refractories in contact with the melted glass are electrofused materials that belong to the Al₂O₃-SiO₂-ZrO₂ system commonly named AZS.Exceptionally for refractory materials the amount of the glassy phase in a AZS material is important and appreciable; and makes them particularly adequate for containing fussed glass. The glass proportion will define much of their properties and behaviors.In the present work the results of the non crystalline phase quantification of two samples of commercial AZS materials are presented and compared. These were obtained by three different methods using in the X ray powder diffraction (XRD) techniques. The first method consists in the linear interpolation of the base lines of the diffractograms compared to the amorphous silica and the fully crystalline quartz. The other two methods are based in the application of the Rietveld method. One is the internal standard method with quartz as fully crystalline standard and the other one consist in the inclusion of the glassy phase to the refinement with a structural model that can be understood as the widening of the peaks consequence of an extreme decrease in the crystallite size of a quartz phase.The three methods showed equivalent results (with differences less than 3%) for the two samples and demonstrated that are adequate for the quantification of the non crystalline phase in this kind of materials.