Material characterization methods quantitative phase analysis

Quantification of the relative abundance of crystalline phases in a multiphase mixture is an everyday problem in a wide range of applications. Common examples are evaluation of the yield in inorganic synthesis and catalytic processes, characterization of raw mineral materials for industrial processes, quality check of fired ceramic products, and many more. While in most cases the required accuracy level of the analysis is a few percent at best, in particular cases such as in the quantification of phase contaminants in technologically important materials, or of hazardous and toxic phases in environmentally dispersed aerosols, the required level of accuracy must be substantially lower than 1 wt% relative abundance. Accuracy levels of 2-3 wt% are commonly reached if standard procedures of quantitative phase analysis by diffraction data are properly performed. Generally employed analytical methods include the internal or external standard method, the matrix flushing method, and the reference intensity ratio method. Very recently, the availability of analysis techniques of powder diffraction data based on full-profile (Rietveld method), originally developed... 

Infrared spectra are now widely used in the examination of pharmaceuticals. The sixteenth revision of The Pharmacopoeia of the United States (U.S.P.) and the eleventh edition of the National Formulary (N.F.) have presented identification tests which used infrared spectroscopy, whereas no infrared tests were used in U.S.P. XV or N.F. X. Infrared spectra have attained acceptance in legal considerations and are now given in patent applications as characteristics of antibiotics of unknown structure. In the pharmaceutical industry there are many applications for quantitative infrared analyses in research and development work, pharmacy research, and in various phases of pharmaceutical production. For example, infrared data are used to characterize reaction conditions and yields, to assay the purity of intermediate products, to examine such problems as the stability of a drug in the material in which it is suspended, and to maintain quality control in the chemical production of bulk drugs. A recent review (Papendick et al, 1969) has given many references to fractionation and isolation methods for pharmaceutical analysis, such as the various types of chromatography, electrophoresis, countercurrent distribution, and extraction. The authors presented many references to infrared analyses for a wide variety of compounds (Table 16.1). 

X-ray powder diffraction is a nondestructive technique widely used for the characterization of micro-crystalline materials. The method has been traditionally applied for phase identification, quantitative analysis and the determination of structure imperfections. In recent years, applications have been extended to new areas, such as the determination of... 

Recent developments and prospects of these methods have been discussed in a chapter by Schneider et al. (2001). It was underlined that these methods are widely applied for the characterization of crystalline materials (phase identification, quantitative analysis, determination of structure imperfections, crystal structure determination and analysis of 3D microstructural properties). Phase identification was traditionally based on a comparison of observed data with interplanar spacings and relative intensities (d and T) listed for crystalline materials. More recent search-match procedures, based on digitized patterns, and Powder Diffraction File (International Centre for Diffraction Data, USA.) containing powder data for hundreds of thousands substances may result in a fast efficient qualitative analysis. The determination of the amounts of different phases present in a multi-component sample (quantitative analysis) is based on the so-called Rietveld method. Procedures for pattern indexing, structure solution and refinement of structure model are based on the same method. 

Wet chemical analysis is used, for example, to characterize the incorporation of foreign elements into the anode or cathode structure. Its advantage is that quantitative amounts can be analyzed, but the method is (i) destructive, (ii) cannot locally resolve the analysis, such as characterization of the cathode but not whether the foreign element is in the cathode, at a phase boundary, or in the current collector, and (iii) complex because it has to be discovered what sample preconditioning is necessary, for example, what acid leaching works, what acid or acid mixture dissolves all the material, and whether other components that should not be dissolved are also in the solution for example, if the cathode material is dissolved, Ni may also be partly dissolved. 

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