Effect of calcium bromide hydrate on the structural and optical properties of polyethylene glycol/niobium pentoxide polymer layers

The blend polymer layers of polyethylene glycol with various Nb2O5 and CaBr2⋅xH2O concentrations were synthesized using the solution-dropping process. X-ray diffraction spectra revealed polyethylene glycol peaks, which could be attributed to the polymers' inherent semi-crystalline phase. The Raman spectra revealed stretching Nb–O bonds and confirmed the Nb2O5 phase. The stretching modes of the CH, CH2, and CH3 groups are presented for polyethylene glycol. Adding more CaBr2⋅xH2O (0–3 wt%) increases the transmittance values to about 0.64 %, 1.18 %, 2.79 %, and 6.29 %. At the same time, the band gap values of the polymer layers go down from 3.0 eV to 2.06 eV. The refractive index values increased from 6.16 (0 wt% CaBr2⋅xH2O) to 7.46 (3 wt% CaBr2⋅xH2O). The low Urbach energy of 837.26 meV for the 2 g polyethylene glycol/4 wt% Nb2O5/1 wt% CaBr2⋅xH2O sample confirms the appropriate concentration of less disorder in the polymer layer.