Cerium (III) doping effects on optical and thermal properties of PVA films

摘要

Cerium chloride (CeCl_3) doped polyvinyl alcohol (PVA)films were prepared by casting technique. The effect o fCeCl_3 concentrations on the structural, optical and thermal properties of the PVA films was studied by X-ray diffraction (XRD), FT-IR, UV-visible, transmittance (T), reflectance (R), differential scanning calorimetry (DSC) and thermogravimetry (TG). Both of the XRD and the DSC results affirm the increase in amorphousity. Absorption spectra of the doped films have shown an absorption band at 260 nm assigned to the trivalent state of cerium ions. Absorption, transmittance and reflectance spectra were used for the determination of the optical constants. The results indicate that the optical band gap (E_g) was derived from Tauc's extrapolation and decreases with the cerium content. The refractive index increases with monotonic behavior has the cerium content increases. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple-DiDomernico model for obtaining the dispersion parameters. The obtained optical parameters were found to be strongly affected by CeCl_3 dopant. Thermal analysis showed that the thermal parameters of PVA are enhanced by CeCl_3. The dependence of the activation energy of the decomposition temperature on doping level was estimated.