Hi Samira Barouni, thanks for arising this discussion.
Do you mean your pellet crack after sintering process? In a ceramic sample, part of sample fly away can be described in the shrinkage of the ceramic due to high sintering temperature. The mass loss might be the chemical decomposition of certain compounds and formation of new phase. Perhaps you can read my previous article which might help you in developing your fundamental knowledge for dielectric measurements:
Article Impact Factor(JCC): 1.4507 - EVOLUTION OF DIELECTRIC CERAMIC...
Article Complex dielectric modulus and relaxation response at low mi...