Currently i am doing some research on optical properties of a oxide material and for that purpose i have done some photoluminescence study on it. Because this is an ongoing research i cant divulge much information here. I have used "$Ex$" excitation wavelength for getting emission spectra for my oxide sample. I have prepared two types of oxide samples one is heat treated and the other not heat treated. After taking emission spectra data for both the samples I got peaks similar to this
Samples Peak wavelength (nm) Non Heat treated a, b Heat treated b,c,d,e
*a,b,c,d & e are wavelength where emission peaks detected
Both samples (heat treated and non heat treated) has same chemical composition which i confirmed using powder XRD. As you can see from the data the heat treated sample has more emission peaks comparing to non heated samples. I can understand from this data that heat treatment to the sample causes increased defects in the sample. what i thought was that after heat treating a crystalline material; the defect in that material should decrease and not the other way round? Is my rationale wrong. Why heat treated sample has more defects?