Importing .crc data from AZtec with correct orientation - hexagonal system

[Emilia Jarochowska]

Hi everyone,

thank you for piles of useful information that had been posted in this group. I am afraid my problem is trivial, but I've combed related posts on the forum and still not sure about the solution.

I am importing AZtec data for which some pole figures had been produced for me, so I can compare if my orientation is correct. I also know sample coordinate system used for acquisition and it corresponds to option 1 in the import wizard

{

setMTEXpref('xAxisDirection','east');

setMTEXpref('zAxisDirection','outOfPlane');

}

The initial data contains:

{

crystalSymmetry('6/m', [9.5 9.5 6.9], 'X||a*', 'Y||b', 'Z||c*', 'mineral', 'Apatite', 'color', [0.53 0.81 0.98]),...

  crystalSymmetry('6/m', [9.4 9.4 6.9], 'X||a*', 'Y||b', 'Z||c*', 'mineral', 'Hydroxylapatite', 'color', [0.56 0.74 0.56])};

}

and after import and setting everything to apatite (for simplicity now), it is

{

 Phase   Orientations  Mineral         Color  Symmetry  Crystal reference frame

     1  343324 (100%)  Apatite  LightSkyBlue       6/m        X||a*, Y||b, Z||c

}

Which looks about right, but it still needs rotation by 180° around the z axis, as in this discussion: https://groups.google.com/d/msg/mtexmail/GOCWevnQLvQ/BglWiMBACAAJ

After this rotation, you can still see in the pole figures a rotation of ca. 30°, but I don't understand where this comes from. Should I just correct this rotation or how can I check whether my import was correct? I don't have access to AZtec at the moment.

Thank you and all the best,

Emilia

[Vivian Tong]

Hi Emilia, 

The coordinates in the Aztec program (Slide1.png) show the XY coordinates with the sample oriented in the SEM chamber. But setMTEXpref() is setting the coordinates in the SEM image.

Do you know how the sample relates to your SEM image coordinates? In some SEMs, the image is scanned 'bottom to top' up the tilt direction, which means that 'xAxisDirection' points west in the EBSD map (and Y points down, and Z still points out), because your SEM image scan starts at the top of your computer screen.

If that is the case, you should set 

{

setMTEXpref('xAxisDirection','west');

setMTEXpref('zAxisDirection','outOfPlane');

}

That is just my guess, it would be good to check this when you can. A complete calibration method can be found in this paper https://www.sciencedirect.com/science/article/pii/S1044580316300924. 

(A quick way to check ONLY the scan direction would be to image a tilted sample at very low mag, and see where the working distance is shorter or longer at the top/bottom of your image. Not doing the full calibration is a bit risky, as some sign errors cancel out!)

Since you are acquiring the dataset in Aztec (not EDAX), you shouldn't need the 180 degree rotation in the other discussion.

Vivian