Citation & Copyright (to be inserted by the publisher) Quantitative Phase Analysis of Ceramic Raw Materials Using a Nonnegative Least Squares Routine C. Coelho 1,2 , N. Roqueiro 3 , D. Hotza 2,3 coelho@unisul.br 1 University of the South of Santa Catarina (UNISUL), Campus Pedra Branca, 88130-000 Palhoça, SC, Brazil hotza@materiais.ufsc.br 2 Graduation Program in Materials Science and Engineering (PGMAT), Federal University of Santa Catarina (UFSC), P.O. Box 476, 88040-900 Florianópolis, SC, Brazil nestor@enq.ufsc.br 3 Department of Chemical Engineering (EQA), Federal University of Santa Catarina (UFSC), P.O. Box 476, 88040-900 Florianópolis, SC, Brazil Keywords : Ceramic raw materials, phase composition, quantitative mineralogical analysis, rational analysis, nonnegative least squares routine Abstract. Combining quantitative chemical composition and qualitative mineralogical analysis, information enough can be obtained to solve the problem of quantitative determination of mineralogical phases. This concept is usually known as Rational Mineralogical Analysis. In this paper, a method using the nonnegative least squares routine for solving a system of linear equations is proposed, as a fast and reliable alternative to the quantitative analysis by X-ray diffraction. Introduction Reformulation techniques for ceramic bodies have been developed to permit varying the body composition to change physical properties, substitute raw materials, or to reduce batch cost. The linear programming can be used to reformulate an existing body rather than to develop a totally new body, reducing the amount of experimentation required by conventional methods [1,2]. The quality of ceramic bodies can be improved if the relationships between the characterizing parameters of raw materials and the physical properties of products are known. Two important but not exclusive parameters in order to describe either a constituent material or a ceramic body made up of a number of materials are chemical analysis (weight or mole percent) and mineral phase (weight percent). For using such techniques, which can be computadorized [3], quantitative input is necessary. This is no problem, for example to chemical analysis or particle mean size, but can be critical when no quantitative phase analysis is available. In the analysis of a multicomponent material by chemical and spectroscopic methods elemental composition can be obtained, but usually great difficulties are faced in distinguishing the chemical identity of the various components-phases present in the material and in determining the amounts of particular phases. X-Ray powder Diffraction (XRD) seems to be a good technique for the analysis of a multicomponent material. Each crystalline component of the material gives its characteristic diffraction pattern independently of the others, making it possible to identify the components of interest. The intensities of diffraction lines of each component are proportional to its amount, except for the absorption correction, so that an appropriate quantitative analysis can be performed.