Accuracy in Rietveld quantitative phase analysis: a comparative study of strictly monochromatic Mo and Cu radiations.
This study reports 78 Rietveld quantitative phase analyses using CuKα1, MoKα1and synchrotron radiations. Synchrotron powder diffraction has been used to validate the most challenging analyses. From the results for three series with increasing contents of an analyte (an inorganic crystalline phase, an organic crystalline phase and a glass), it is inferred that Rietveld analyses from high-energy MoKα1radiation have slightly better accuracies than those obtained from CuKα1radiation. This behaviour has been established from the results of the calibration graphics obtained through the spiking method and also from Kullback-Leibler distance statistic studies. This outcome is explained, in spite of the lower diffraction power for Mo radiation when compared to Cu radiation, as arising because of the larger volume tested with Mo and also because higher energy allows one to record patterns with fewer systematic errors. The limit of detection (LoD) and limit of quantification (LoQ) have also been established for the studied series. For similar recording times, the LoDs in Cu patterns, ∼0.2 wt%, are slightly lower than those derived from Mo patterns, ∼0.3 wt%. The LoQ for a well crystallized inorganic phase using laboratory powder diffraction was established to be close to 0.10 wt% in stable fits with good precision. However, the accuracy of these analyses was poor with relative errors near to 100%. Only contents higher than 1.0 wt% yielded analyses with relative errors lower than 20%.
Servicios Centrales de Apoyo a la Investigación, Universidad de Málaga , 29071-Málaga, Spain.
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León-Reina
Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071-Málaga, Spain; X-ray Data Services S.L., Edificio GREEN RAY, Primera Planta, Avenida Louis Pasteur 47 (Ampliación Campus Teatinos), 29010-Málaga, Spain.
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García-Maté
Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071-Málaga, Spain; X-ray Data Services S.L., Edificio GREEN RAY, Primera Planta, Avenida Louis Pasteur 47 (Ampliación Campus Teatinos), 29010-Málaga, Spain.
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Álvarez-Pinazo
Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga , 29071-Málaga, Spain.
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Santacruz
ALBA Synchrotron, Carrer de la Llum 2-26 , Barcelona, E-08290 Cerdanyola, Spain.
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Vallcorba
Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga , 29071-Málaga, Spain.
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De la Torre
Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071-Málaga, Spain; ALBA Synchrotron, Carrer de la Llum 2-26, Barcelona, E-08290 Cerdanyola, Spain.
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Aranda
high-energy laboratory X-ray powder diffraction; limit of quantification; spiking method