Differential scanning calorimetry and dielectric properties of methyl-2-hydroxyethyl cellulose doped with erbium nitrate salt

Cast technique was used to prepare thin films of pure methyl-2-hydroxyethyl cellulose (MHEC) and composite samples containing erbium trinitrate [Er(NO3)3] films with concentrations 0.5, 1, 2, 5, 7, and 10 wt%. Differential scanning calorimetry (DSC) was performed on pure materials [MHEC and Er(NO3)3] and their composites of 2 and 10 wt% Er(NO3)3. The new exothermic phase transitions induced in DSC thermograms may be attributed to structural phase transitions. The dielectric constant (ε′), dielectric loss (ε″), and ac-conductivity σac were studied for MHEC and Er(NO3)3 doped MHEC samples as a function of temperature and frequency. The activation energies for both α and σ-relaxation processes observed in ε′ and ε″ for the samples under investigation were calculated. It was found that the value of activation energy calculated for of σ-relaxation process is consistent with that of dc-conductivity for all doped samples in the same temperature range. In addition, the correlated barrier hopping mechanism of the electrons appeared to be the most suitable mechanism to describe the ac conduction behavior in different compositions of the present system.