Calculated Curves for Quantitative Powder Diffraction Analysis in Binary Mixtures, Based on Calculated Diffractograms by the Rietveld Method

摘要

Reference curves for certain binary mixtures were calculated, based on calculated diffractograms, by the Whole-Pattern fitting- and the Rietveld- method. The Instrumental depending parameters were determined using least square techniques by the Whole-Pattern fitting- and the Rietveld- method, from experimental data deriving from standard crystalline phases, like Lab_6 and the minerals used in the binary mixtures, with D500 Siemens diffractometer. For the calculation of a theoretical diffractogram, the crystal structure of the crystalline phases in the binary mixture and the scale factors were used. The scale factor for each phase was calculated using density and mass absorption coefficient of a certain binary mixture. For the quantitative analysis the calculated diffractograms were treated in the same way as the measured experimental raw data. Characteristic reflections were chosen for each phase without overlapping of the reflections of the second phase, and the integral intensities were calculated. Reference curves were calculated for some common binary mixtures in mineralogy, like: Calcite-dolomite, calcite-aragonite, quartz-calcite, hematite-boehmite, hematite-diaspore, boehmite-diaspore, calcite-gypsum, calcite-portlandite, portlandite-lime. The quantitative analysis of the above binary systems was tested by artificial mixtures with known proportions. The accuracy in the quantitative determination was less than 5% relative error. The quantitative analysis by this method gives satisfactory results and is suitable for a quick quantitative estimation of the crystalline phases.