Dear Manikandan,

do you observed only one peak or the pattern of a single phase? Do you have observed the particle morphology? Platelet-shaped particle could give a preferential orientation responsible of the observation of a restricted number of diffraction peaks. Mixed cobalt aluminum oxide exist (for instance the spinel CoAl2O4). For this reason, only one pattern of peak could be observed.

Best regards.

Philippe.

Dear Manikandan Venkatraman

When the volume fraction of cobalt is lower than a certain value, the cobalt is almost completely dispersed as ions in the amorphous aluminum oxide matrix. For that the amorphous aluminum hybrids oxide changes to semi-crystalline form upon cobalt doping. Thus at higher doping volume fraction, the cobalt is dispersed as particles. Hope this explanation is helpful.

Best regards

Maybe the concentration or volume of the respective particle is low to measure the shape by XRD and it has become amorphous in the final result. You can use TEM, SEM, and DLS for your reference with XRD result