Dear Rafael Spaziani ,

your samples have different types of crystal structure.

The selection rules (allowed or forbidden reflections) are due to the property of the structure factor.

See for example:

http://groups.mrl.uiuc.edu/chiang/czoschke/diffraction-selection-rules.html

or

https://en.wikipedia.org/wiki/Structure_factor

or

https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Introduction_to_Solid_State_Chemistry/06%3A_Recitations/6.16%3A_X-ray_Diffraction_and_Selection_Rules

So for example you will have for the FCC lattice (111) as well as (222) peaks present in your pattern (h, k, l all even or all odd),

but for the BCC lattice you will only have (222) peak but no (111) peak;

(h+k+l) = even -> allowed reflection; (h+k+l) = odd -> vorbidden reflection

Please see also the case for FCC Diamond:

here you have (111) allowed [(h, k, l) all odd]; but (222) forbidden [(h+k+l) not equal to 4n]

Best regards

G.M.