Minimization of absorption contrast for accurate amorphous phase quantification: application to ZrO2 nanoparticles
Résumé
Monoclinic and tetragonal zirconia samples were characterized by X-ray diffraction, pycnometry, thermogravimetric analysis (TGA), Fourier transform (FT) IR and mass (MS) spectroscopies, and scanning and transmission electron (TEM) microscopies. The results show, for the particular case of a tetragonal zirconia sample, an X-ray-undetected subproduct identified as an amorphous organic phase by FTIR-ATR (attenuated total reflection) and TGA-MS. The observations by TEM allowed this amorphous phase to be localized on the surface as a shell coating the nanoparticles. Moreover, this amorphous phase was quantified by Rietveld refinement via the addition of an internal silicon standard. Because zirconia and silicon have different linear absorption coefficients, the microabsorption effect was minimized by using small particle sizes. The amorphous phase was calculated to constitute 11.4 (30)% of the initial mass before Brindley correction and 10.6 (30)% of the initial mass after Brindley correction. The closeness of these values shows that the contribution of the Brindley correction can be neglected if precautions are taken on the microabsorption effect. This work has also highlighted the importance of thoroughly characterizing commercial products, which are not necessarily pure. Indeed, the presence of impurities could become a non-negligible parameter for physical and chemical properties studies related to commercial materials.