It could also be that you are forming an amorphous hydroxide.  A number of the very insoluble hydroxides (i.e. aluminum and iron) form amorphous solids when they precipitate from solution, copper could as well.  If I remember correctly, amorphous aluminum  hydroxide will form an amorphous 'hump' centered somewhere between 20-30 degrees 2theta.  I don't remember the 'hump' being as prominent as an amorphous glassy material.

Hi Ahmad,

Not sure about XRD but i suggest if you can perform EDAX and/or XRF just to confirm amount of Cu present in the precipitate . you may want to do single crystal XRD .   

Often the simplest answer is the correct one. In this case that would suggest that you didn't form any (or enough to be detectible) Cu precipitate. What did you form? Seeing the diffraction pattern would be helpful, just to be sure that the SN is sufficient to see Cu if it is indeed there.

It could also be that you are forming an amorphous hydroxide.  A number of the very insoluble hydroxides (i.e. aluminum and iron) form amorphous solids when they precipitate from solution, copper could as well.  If I remember correctly, amorphous aluminum  hydroxide will form an amorphous 'hump' centered somewhere between 20-30 degrees 2theta.  I don't remember the 'hump' being as prominent as an amorphous glassy material.

As said above, if you don't have the XRD signal whether you don't have enough amount of Cu giving a signal, or the sample is amorphous

By 'nothing' I assume you mean no relatively sharp diffraction reflections in the XRD. I assume 'something' is present - an amorphous background signal perhaps. This can still tell you valuable information or at least give indication to other characterisation techniques that may assist.

Amorphous Cu(OH)2 was formed. What is the color of your ppt ? Light blue ? If yes, that means the presence of Cu in that.   Droppjng some aq. NH3 to your ppt., if  a dark blue solution foms, that definitely  gives evidence about presence of copper (ammine complex of Cu will be formed and that has intesive dark blue color) in your sample.

Cu(OH)2 is definitely formed and the size of the colloids depends on many factors including temperature, but youre most likely getting some sort of statistical distribution of particle sizes.  Also it is my understanding, that Cu(OH)2 is not a very stable molecule when isolated to dryness and decomposes.  My guess is that Cu(OH)2 cannot be prepared to get colloids of uniform size for XRD, and if you are isolating the ppt to dryness then it is most likely decomposing.