کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1332232 | 979034 | 2011 | 10 صفحه PDF | دانلود رایگان |
Calcination behavior of nano-crystalline lanthanum chromites doped with calcium and strontium has been probed by Fourier transform infrared spectroscopy, X-ray diffraction and small-angle neutron scattering as a function of temperature. Infrared spectroscopic results imply that over a range of temperatures, some intermediate phase of dopant chromates evolve and then dissolve back, which has also been confirmed by the XRD. Neutron scattering data reveal a fractal type correlation of building blocks in virgin powders. Increase in fractal dimension and reduction in upper cutoff vis-à-vis the densification of agglomerates were found with increasing calcination temperature. Calcination, beyond 900 °C, results in breaking down of the fractal morphology almost completely. Such shrinkage event also results in a modification of the microscopic structure. These changes have been attributed to the compaction of agglomerates of both Ca- and Sr-doped lanthanum chromites, assisted via liquid state sintering by the melting of the intermediate phases at intermediate calcination stages.
Graphical AbstractDopant chromates evolve as intermediate phases during calcination of Ca- and Sr-doped nano-crystalline lanthanum chromites at intermediate temperatures, around 900 °C, evident from infrared spectroscopy. Such an event results in a modification of the microscopic and mesoscopic structures.Figure optionsDownload as PowerPoint slideResearch highlights
► Meso/microscopic structures of La0.7Ca0.3CrO3 and La0.8Sr0.2CrO3 modify during calcination.
► Transient phases CaCrO4 and SrCrO4 appear at intermediate temperatures.
► Bond length, unit cell volume, etc. modify as intermediate phases evolve and extinct.
► Compaction of the agglomerates takes place due to liquid state assisted sintering.
Journal: Journal of Solid State Chemistry - Volume 184, Issue 1, January 2011, Pages 204–213