The dielectric constant of my samples show a sudden drop at around 60degree, whereas they are heat stable and shows no change in phase in DSC TGA. What can be the possible reasons for such change?
Initially increasing temperature free electron/hole pairs which are atrracted towards corresponding electrodes as a result charge accumulation increases. This continues with increasing temperature and the separation(width) between charges on respective elctrode sides gradually decreases and corresponding to a particular temperature, the the separation starts merging and dielectric constant decreases abruptly with further increase in temperature
This happened due to the moisture effect. Hygroscopic NPs absorbs moisture from its environment. This moisture released during the temperature variation measurements.
Dry your sample at around 70deg C to eliminate this effect.
More details are needed such as:
What is your sample?
Is it ceramic, polymer, or composite?
Also, please attache the TGA and DSC thermographs.
My samples are ceramic based with phase change beyond 1100degree and hydrophobic.
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