It depends on the thickness of desired pellets. Please specify that first.

Dear Jadoon,

pellets of carbon particles are understood, but you are saying graphene, which is only called for a single layer of carbon, if you make pellet that becomes bulk...do you mean incorporating graphene in carbon particle for the conductivity study???

The size does not really matter. Smaller will make the measurement a bit less accurate, that's all, but referring to a conductivity, you are supposed to measure an intrinsic property independent from sample size and shape. More important is the pressure. Higher pressure means less porosity and far better electrical contacts between the grains, hence the much high conductivity. So pressure needs to be carefully controlled, otherwise the results will be totally irreproducible, and comparison with other materials will be meaningless. This is a complex matter.

Alain

thanks Alain Celzard,Dillip Kumar Mishra and Ayush Khare for kind suggestion. Dear Mishra I am using corbon and graphene composite for conductivity measurements...so how much sample I need for these pellets..

Dear Mr. Shahid, 

For making 13 mm diameter and approx 2 mm thickness pellet, I have used about 10 g of the sample for ZnO.

I sincerely hope, it will be more or less same in your case also.

All the best.

thanks Dear Arindam Ghosh,,, but I am working with corbon and graphene for which this much amount (10g) is not possible...I hardly prepared 1 g in so many reactions...by the way thanks for kind information...

thanks Dear Astro Karthik for valuable coment...

Dear Shahid,

I hope the answer is not too late for you but in my opinion if you want to make a composite of graphene and carbon for electrical measurements the best way is to make a suspension of them followed by a filtration process to make a sheet-like composite. The thickness of the film can be modifiy by changing the amount of the filtered solution (best to keep the solution with low concentration as it is much better for the mechanical resistance of the final film). Such composite can be pelled-off from the filter for subsequence fourth-points measurements.

Best wishes

Cuong