In case of my XRD characterization, the bulk density and X-ray density decreased while porosity increased after substitution of Manganese in Cr2O3. So, how can i justify these results?
Dear Dr. Rishabh Sharma
Regards
The volume-mass density is a powerful tool used to characterize any material (of any form bulk, thin films or powder) and its ability also to explore any changes in the crystal structure of the crystalline material. It can be calculated theoretically from X-ray diffractograms using the following equation:
ρx = n.Mw / (NA.V)
where n is the number of atoms per unit cell, Mw is the molecular weight, V is the volume of the unit cell and NA is Avogadro's number.
Please go to this link to read more about this issue.
This equation can be used to calculate the density of any material of any form, bulk, thin films or even if it is a powder.
For more details , please go to this paper:
Article Improving microstructural properties and minimizing crystal ...
https://www.researchgate.net/publication/320934775_Improving_microstructural_properties_and_minimizing_crystal_imperfections_of_nanocrystalline_Cu2O_thin_films_of_different_solution_molarities_for_solar_cell_applications [accessed Jun 03 2018].
Good luck
Dear Adnan Afzal
Have a nice day and good times
X-ray density ρx of thin film samples can be estimated by using the following relation that suggested by Smith and Wijn:
ρx = C.M / (NA.a3)
where M is the molecular weight, NA is Avogadro’s number C is constant dependent on the crystal structureof the sample and it is equal to the number of the lattice points per unit cell while (a) is the lattice constant. . As evidence, the ρx is inversely proportional to the cubic power of the lattice constant, so the X-ray density can be changed where (a) may be changed by affecting the preparative conditions.
Good luck
when you determine the crystal structure by XRD analysis, you also determine the cell volume (from cell parameters) and its mass (given by the cell content, that is the type and numebr of atoms within the cell). So you can calculate the density of your compound. Nonethelss, different samples with a same composition can be characterized by a different bulk density, on account of a different porosity. Likely in your XRD density case, the substituting Mn (characterized by a larger ionic radius than Cr) increases much more the volume (I guess on account of structural distortion) than the mass
Hi Adnan, do you replace a) a large amount of Cr by Mn or b) only a little fraction?
In case a) I would assume increasing x-ray density (increase of opaqueness) combined with a little increase of density. In case b) I think that due to the larger Mn ionic radius (see Alberto above) a lot of lattice defects will show up, which can end up in marcoscopic porisosity and thus reducing the overall density and x-ray density. The expected increase of x-ray attenuation by the subsitution of Cr atoms probably is competed by the upcomming poriosity of the sample.
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