I have an alloy sample and the selected area diffraction pattern of this alloy is showing polycrystalline rings. How do I calculate planes from those rings?
Dear Dinesh,
the inverse diameter or radius of the diffraction rings is directly proportional to the corresponding interplanar spacing. To determine the d_hkl you need to calibrate your diffraction pattern. The calibration can be in terms of the diffraction angle theta, then you can apply the Bragg equation to calculate the d_hkl. This approach is similar to XRD. For TEM it is more common to scale in reciprocal units e.g. the lenght of your diffraction vectors [1/nm]. The inverse length of the measured distance corresponds to the d_hkl.
However, for both approaches you will need a calibration standard. That means a sample where the d_hkl and their corresponding diffraction rings are well known. Please ask the operator or your supervisor if already done.
I appended a slide from my lecture visualising my explaination including a formula that approximates the relation - it is reallly basic. You will also find this in each Textbook about TEM.
Cheers
Martin
Dear Dinesh,
the inverse diameter or radius of the diffraction rings is directly proportional to the corresponding interplanar spacing. To determine the d_hkl you need to calibrate your diffraction pattern. The calibration can be in terms of the diffraction angle theta, then you can apply the Bragg equation to calculate the d_hkl. This approach is similar to XRD. For TEM it is more common to scale in reciprocal units e.g. the lenght of your diffraction vectors [1/nm]. The inverse length of the measured distance corresponds to the d_hkl.
However, for both approaches you will need a calibration standard. That means a sample where the d_hkl and their corresponding diffraction rings are well known. Please ask the operator or your supervisor if already done.
I appended a slide from my lecture visualising my explaination including a formula that approximates the relation - it is reallly basic. You will also find this in each Textbook about TEM.
Cheers
Martin
You might need to know the camera length of your TEM. This is the constant used to calculate the real space-d based on the recriprocal space where you can measure the ring diameter. They have an inverse relationship,i.e. the larger the ring, the smaller distance it correspond to in the real space.
You can follow these steps:
1. Download Fiji
2. Help-> Update-> TEM suite
4. Restart Fiji
3. Draw the concentric ovals to the 0 point and press m after.
4. Go to the TEM option that appears and select Calc d Space.
5. The D spacing will be provided in Amstrongs, you can go to your reference to know the diffraction points.
https://imagej.net/Calc_dSpace
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