Microstrain in nanostructured nickel oxide studied using isotropic and anisotropic models

X-ray diffraction line profile analysis of nanostructured nickel oxide: Shape factor and convolution of crystallite size and microstrain contributions

“…Two types of lattice strains are associated with nanocrystalline materials [4,5]. First kind extends over the entire lattice and is manifested as a shift in the position of the XRD peaks while the second kind extends only over a few lattice spacings and is often referred to as 'microstrain' or 'localized lattice strain' [6]. Microstrain originates due to the presence of defects such as vacancies or cores of vacancies in the lattice, excess fraction of grain boundaries, etc., and causes broadening of the XRD peaks [2,[5][6][7].…”

“…Thus microstrain is a measure of the concentration of defects in the sample. In the case of systems such as nanostructured transition metal oxides where the presence, concentration and distribution of cation/anion vacancies could precipitously affect the physical and chemical properties, microstrain could be used as an indirect measure of the concentration of defects in the sample and hence could be a useful structural parameter for structure-property correlation [2,6].…”

“…Also, the anisotropic nature of the elastic constants of the crystal can be incorporated in the Williamson-Hall analysis by using uniform deformation stress (UDSM) or uniform deformation energy density (UDEDM) models [8,12,13]. A number of reports on the Williamson-Hall analysis of nanostructured samples of different kinds have appeared in the literature in the recent past [6,[12][13][14][15][16][17][18][19][20][21][22][23]. A perusal of these reports reveals that models which take into account the anisotropic nature of the crystal, viz., UDSM and UDEDM often more correctly model the system than the one which does not take the anisotropy into account viz., UDM [6,[13][14][15][16][17]20].…”

“…A number of reports on the Williamson-Hall analysis of nanostructured samples of different kinds have appeared in the literature in the recent past [6,[12][13][14][15][16][17][18][19][20][21][22][23]. A perusal of these reports reveals that models which take into account the anisotropic nature of the crystal, viz., UDSM and UDEDM often more correctly model the system than the one which does not take the anisotropy into account viz., UDM [6,[13][14][15][16][17]20]. Further, it was also noted that in the case of samples with smaller crystallite sizes, less than $ 10 nm, the scattering of the points about the linear fit was markedly more, implying low value for correlation coefficient [3,19,20].…”

“…Further, it was also noted that in the case of samples with smaller crystallite sizes, less than $ 10 nm, the scattering of the points about the linear fit was markedly more, implying low value for correlation coefficient [3,19,20]. For samples with larger average crystallite sizes the correlation is usually very high [6,12].…”