we obtained two different particle size using XRD and SEM
XRD shows particle size of 40 nm
while SEM reveals particle size of 20 nm
is it reasonable to find such differences in particle diameters? if so please refer me corresponding references
Thank you
XRD method used for obtaining the crystal size and SEM have been used to obtain particle size. We cannot compare the crystal size measurement from XRD with the particle size measurement from SEM. Therefore result obtained of SEM is true.
XRD method also dependent on particle shape. If there is a difference in particle shape size through SEM and XRD then its not a big issue. SEM and TEM Analysis are more appropriate methods for the estimation of particle size. XRD can only estimate. A more better XRD methods can be be William Hallson Method. Advancements in Scherrer Models have also been devised in literature.
Comparison of crystallite size using XRD would mostly be different from particle size obtained using other techniques. For particle size TEM or AFM would also be useful.
Totally agree with Prof. Findik above.
They have talked a lot on XRD's problems, but SEM also have a edge effect, caused by loss of the SE signals. These SE could easily be sheltered by up-and-down micro-structure around the particle. So the edge we see in a SEM image is sometimes not the real boundary of the particle. This kind of edge effect could not be waived if the particle size went down to nano scale.
TEM and the direction Z of AFM do not have this kind of problem, so they could be the best reliable answer for
Agreed with previous answers that its better to use TEM than SEM. Because your results shows that the size from XRD is higher than from SEM. Crstallite size not particle size from XRD in the best case can be equal to the particle size from microscopic measurements (when the nanoparticles are very small) but can never be higher. So i guess there is some error in the observations from SEM as suggested by others.
So you should go with TEM for the exact particle size.
Using the Sherrer Equation, XRD data can be used to estimate the crystal size of a nano particle. Although, this method is only used in absence of electron micrographs (TEM or SEM) as the precision of this method is low. Furthermore, the method only works for nano crystals but not for micro crystals, as its results are mainly in nano range. SEM on the other hand gives higher precision of particle size of a material while the TEM gives high precision crystal size of the material, irrespective whether it is nano or micro particle.
There are some problems here.
You cannot measure particle size by XRD only the mean scattering domain size (which has annoyingly been called 'crystallite' size - and this creates a LOT of misunderstanding that been discussed on these pages ad nauseam).
You should never to be able to obtain a size from XRD that is larger than that measured by EM. We need to find the source of your errors.
Please post your images of the particle size measurements, and then also post the XRD data and your working that has generated this value. Please give as much information as you can and we may be able to help.
`Dear Foad
The crystallite size by XRD must always be less than the particle size by SEM. There is some errors in your calculations.
The particle tested by XRD is crystallize size, or named primary particle, which is a single crystal particle. The particle tested by SEM usually is a particle consisted of one or two, even more primary particles.
You can estimate the diameter of the particle by the Scherrer equation than you compare it with TEM.
Sorry, I just read your message today.. Here are some publications
Williamson-Hall analysis in estimation of lattice strain in nanometer-sized ZnO particles
A comparison between TEM measurements and XRD Measurements have been provided here. Its an open access paper.
As stated by several scientists, the problem with your findings is that the "particle size" is less than the "crystallite size". In the question, I did not find enough information regarding how the "crystallite size" was evaluated. If for example Scherrer equation was used with the constant K = 0.94 (which is usually adopted by various workers), Then one must be careful that the analysis in deriving such a constant was based on the assumption that the contributions of coherent scattering from the three crystal-axis directions to the integrated intensity had a Gaussian shape. Therefore, if the reflection was fitted with a different line-shape, a significantly different result would be obtained. Lorentzian line-shape for example would give a mean structural coherence length of about 35% smaller. Further, the size obtained from (hkl) reflection is a measure of the mean structural coherence length along the direction. If the "particle" is not spherically symmetric in physical shape (Platelet for example) then the evaluated "size" would depend on the (hkl) reflection used for the calculation. The mean structural coherence length in the plane of the plate could, in principle, be larger than the physical thickness (measured by SEM for example) of the "particle". It all depends on how and what you had measured using the different techniques.
I believe that this discrepancy is due to nano-particle distribution. The mean size is defined as Lm=ΣLj/N, where Lj is the size of the "j" particle. In SEM micrograph, I assume that you observe numerous particles of smaller size and a few of larger. When you make the particle distribution, you observe a peak at some value Lp. When the distribution is purely normal (Gaussian), the two values (Lm & Lp) coincide. However, this is not the case, when the distribution is not symmetrical, with long left or right tails. The larger value of skewness, the larger the deviation between Lm and Lp.
In your message, you do not give any details on how nano-particles are formed. If you are using ball-milling, the nano-particle distribution is more likely log-normal, which means that it has a long right-tail. The mean size value is not the same with (so called) "mode" value, which corresponds to the point of maximum (see picture in https://en.m.wikipedia.org/wiki/Log-normal_distribution#/media/File%3AComparison_mean_median_mode.svg).
Similar findings (XRD-determined mean size is larger than TEM-determined one) was observed in the Fabrication of nanocrystalline Mg2Si via ball milling process: structural studies (M Ioannou et.al, Powder Technology 217, 523-532, 2012). At extended ball milling, when distribution becomes more symmetrical and more Gaussian-like, the two values tend to coincide.
I hope that this helps.
Dear
XRD is used to identify crystal size and SEM is used to identify particle size.....................
I do not understand the question. Because crystallite size is completely different than the particle size. Unless the particle is a single crystal. You write the crystallite size is larger than the particles. Please note that a XRD is a method for indirect and direct SEM. XRD provides information of the volume and SEM of the surface. It may therefore find that you have a mixture of particles of various sizes but that's just a guess.
"XRD shows particle size of 40 nm" - Share your computations and assumptions for best feedback. What method did you use?
XRD starting with SAXS and then WAXS may be used to precisely estimate various correlation lengths and distributions in situ in the sample.
https://www.flickr.com/photos/85210325@N04/10221065324/in/album-72157645018820696/
https://www.flickr.com/photos/85210325@N04/10515372183/in/album-72157645018820696/
"It is better to use AFM and TEM instead of using XRD and SEM."
This topic & related issues have many active & interesting discussion on RG. In my opinion, there is value in each method and they help in combination to unlock the various Nano structural secrets in materials. Conventional XRD methods may qualify for your antagonism but modern 2D real time XRD microscopic methods will certainly change your mind. The significant difference between XRD and all other methods is the in situ NDE nature of the XRD techniques.
Dear colleague Buazar,
Crystallite Size is Different than Particle Size. A particle may be made up of several different crystallites or just one crystallite so in this case (particle size = crystallite size)
Crystallite size often matches grain size, but there are exceptions
Crystallites are coherent diffraction domains in X-ray diffraction.
Particles are chunks/pieces (usually very small, below 1 mm) of solid matter, ensembles of atoms. Particles can be as small as two atoms (the nitrogen particle for example, N2)
Grains are volumes, inside crystalline materials, with a specific orientation.
Particles can be polycrystalline, single crystal or amorphous. A 100 nanometer particle of gold, for instance, can be made of:
a single gold crystal,
many grains with a grain size
Dear sir,
How we can calculate particle size from SEM.. and in TEM they given Bar scale on the image it is a particle size ...??
I think this link can help
http://www.instanano.com/characterization/theoretical/xrd-size-calculation/
No they can not provide same size.
The sherer formula used for xrd crystalline will surely be different from the absolute measured SEM.
XRD shows the crystal size, but SEM shows the particle size,
So you can not compare them together.
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography
- X-ray Diffraction
- XRD Analysis