Hi Shivesh,

There are a couple of potential reasons depending on why there are lower proportions of SiC in the sample. Generally, if the concentration is lower it is more likely that lower intensity reflections are become indistinguishable from noise. It may also be less crystalline due to a variety of reasons meaning that long range order for a specific set of indicies is lost. Alternatively, you may have a preferred orientation issue with your sample preparation, decreasing the intensity of some reflections relative to others.

This is almost definitely not an exhaustive list but covers most of the basic reasons for missing peaks.

Cheers,

Laurence

Dear Mr Sareen,

Besides the reasons pointed out by Mr Dyer, another one could be the higher background of your XRD pattern cause for example by fluorescence. You could cope with this problem by changing the X-ray emission.

Wish you good luck!

Best regards,

Maria

May be the sample is amorphous，you can smooth the XRD curve

The main compound (component) in your sample will appear in XRD if it is in crystalline phase. other minor components may appears as impurities (additional small peaks) (undefined peaks). most peaks of the comound usually appears in XRD not all the peaks even if it is in crystalline phase. Moreover, the compound not appear in the XRD if its percent is less than 3-5%

As point out by Eman Bayoumi, XRD peaks will not appear for SiC , if it is less than 5%. 

Other reason could be, the less intensity peaks  cannot be observed in the pattern if  the other compound is highly crystalline posses high intense  XRD peaks.  For example, if the other compound XRD peak intensity is 10,000 counts and SiC intensity count is  50 or less . Then SiC peaks will exist but due to high intensity of other compound, it cannot be observed.