Sorry, but certainly. The morphology of grains, crystals, aggregates in SEM and powder diffraction are completely independent things. For example, such pyrite. Cubic, octahedral crystals, as well as recrystallized bacterial precipitates, etc., have the same atomic arrangement and therefore the same diffraction pattern, but are morphologically different.
Alimohammad Dehghan Manshady be careful not to confuse concepts like crystallite size (determined by XRD) and grain size (determined by SEM).
Sample roughness may influence some Rietveld results (e.g., thermal parameters); see [Powder Diffraction, 8(2), 74-83].
Particle size may affect the XRD pattern, for instance by inducing preferred orientation if you have large particles.
Anyway, SEM (without EDS) basically gives you information about the morphology of the particles, besides analyzing the material on a scale several orders of magnitude greater than XRD.
In [1] you can stand on a good example for reference:
Figure 2 shows the diffraction peaks indexed according to JCPDS N° 45-0937, indicating that the monoclinic CuO phase was obtained for both two samples CuNH05 and CuNH05..
The SEM images for both samples present plate-like particles morphology, but the difference between the two samples is in the agglomeration.
Figure 4 of CuNH05 sample: the agglomerates present quasi spherical form. For the CuNa05 sample figure 5: the small plates above large plates resulting in the interconnected channels.
With these results it is evident that the agglomeration´s morphologies of the copper oxide CuO synthesized was differentiated as a function of the mineralizing agent used in the synthesis methodology.
For that you can say yes, it is possible to have same XRD pattern but different SEM morphology.
Yes, you may obtain the same XRD pattern of the material prepared by different methods. But there should not be any additional phase present. However, the morphology obtained from SEM differs as the morphology of the sample depends on the preparation method adopted.
Now, come to your next question: could it be concluded that just the XRD pattern itself would specify the synthesized material? Yes, the XRD pattern itself specifies the synthesized material e.g. formation of the sample, crystallite size, lattice parameter etc. However, if you are interested in morphology, microstructure etc. we can go for SEM, HR-TEM etc.
Now, come to your next question: we should pay attention to also FTIR or Raman or ....If your sample contains different types of functional groups and modes of vibrations, you can also adopt techniques like FT-IR, RAMAN, etc.