Hi XRD and TEM experts
It doesn't make sense to me but I still wanted to see if it's possible to have XRD crystallite size bigger than TEM particle diameter. I'm talking about high BET oxide nanoparticles. XRD Rietveld refinement using the integral breath CS in Topas for a few samples gives CS 6-8 nm, while TEM for the same samples gives 4-5.5 nm.
The other way around is expected: XRD CS's should be smaller (or maybe equal) than TEM diameter. The particle size distribution seems pretty big but I think that will equally affect XRD and TEM (if adequate particle statistics is used).
Please educate me on this.
Is using Scherrer CS worth trying if I'm dealing with a material which has index-dependent FWHM due to planar defects?
What do you think is the estimated error in crystallite size for your XRD-derived answer? Given what I know about this, I suggest your XRD results are in excellent agreement with the TEM result.
Hi Edward Andrew Payzant,
The error for the XRD-derived values are between 3 and 8%, so the TEM-derived values still fall outside (and below) the XRD error ranges.
Why would you confidently suggest there is excellent agreement?
Jamal Nasir yes I would still confidently suggest there is excellent agreement. This is for several reasons (including more than 3 decades of experience), the main ones being that (1) we are comparing apples and oranges here - the TEM samples a relatively small number of grains, whereas XRD averages a huge number, and most important (2) the XRD-derived crystallite size is a simple calculation based on a simple model that rarely applies to real materials, and so I would suggest that if you think your XRD size error is "between 3 and 8%", then you need to think again - that would imply that the "error" for your examples, i.e., 6-8nm crystallite size, is +/- 0.2nm, which is a statistical error based on least-squares fitting parameters and is not actually the probable error in crystallite size, which is almost certainly an order of magnitude larger, i.e. +/- a few nm.
Steven Van Petegem great suggestion - that paper by Matteo Leoni et al. is particularly good.
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