Material characterization methods lattice parameter determination

X-Ray and electron diffraction measurements have been most usually used to characterize the phases present in any reactant mixture, and provide a means of identification of solid reactants, intermediates and products. In addition to such qualitative analyses, the method can also be used quantitatively, with suitable systems, to determine the amounts of particular solids present [111], changes in lattice parameters during reaction, topotactical relationships between reactants and products, the presence of finely divided or strained material, crystallographic transformations, etc. 

The lattice parameters are the averages of millions of unit cell dimensions in the specimen and are important in characterizing materials. A precision of 1-0.1 % can be obtained rapidly using routine methods. Higher precision measurements of the order of 0.01 % or better are required to determine the coefficients of thermal expansion and in a variety of other studies. The indexing of complex powder patterns requires precise measurements of many reflections in the low-angle region. 

Since there is usually a fairly simple relationship (approaching linearity) between lattice parameter and composition of solid or crystalline solutions, precision measurements of the separation and relative intensities of the lines provide an important and widely used method of materials study and characterization. If proper precautions are observed, one can determine chemical compositions from these structural data sensitivities of 0.1 cases. 

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