Ann Mary Jose no, the XRD intensity peak of magnesium-doped ZnO (MZO) is generally lower than that of undoped ZnO.Magnesium ions can lower the ZnO lattice's peak intensity. In addition, substitutional doping, Mg doping, grain sizes, surface roughness, and quantum confinement effects affect diffraction signals.
Al-Khalqi, E. M., Abdul Hamid, M. A., Al-Hardan, N. H., & Keng, L. K. (2021). Highly sensitive magnesium-doped ZnO nanorod pH sensors based on electrolyte–insulator–semiconductor (EIS) Sensors. Sensors, 21(6), 2110.
Kara, R., Mentar, L., & Azizi, A. (2020). Synthesis and characterization of Mg-doped ZnO thin-films electrochemically grown on FTO substrates for optoelectronic applications. RSC advances, 10(66), 40467-40479.
it is possible for the XRD intensity peak of magnesium-doped ZnO to be more than the undoped ZnO. The intensity of the peak can be affected by various factors such as the concentration of magnesium, the synthesis method, and the temperature.
in the case of preferred orientation/texture (such as in film samples), that might happen...
Which type of sample do you consider? Film or powder ?
But also crystallite sizes (and residual stress) affect the peak heights via the peak broadening... There is no guarantee that the crystallite sizes of both samples are identical.
In the case of thin films even the film thickness affects the (absolute) peak intensity.
You may show your XRD pattern and share some details about your sample(s)...
The XRD data was collected in the same measurement and with the same parameters and equipment/instrumentation?
Usually, the modification of the peaks by doping agents is a displacement in 2θ by the modification of the lattice parameters and the broadening induced by distortions in the lattice, new preferential orentation growth, sample presentation (powders or thin films) and so on, or as was said above the dopant concentration, may be a supersaturation of magnesium, since the scattering factor of Zn is higher that Mg. If you provide more details of your issue, we can help better.