Synthesis and characterization of La3+ ions incorporated (PVA/PVP) polymer composite films for optoelectronics devices

Polymer rare-earth composite films PVA/PVP-xLa(3+) (xwt%; x = 0, 3, 5, 10, and 15) were fabricated by the solution casting method. The structural parameters of these films were determined from X-ray diffraction (XRD) pattern analysis, and the complexation of La3+ ions with the polymer composite films was studied by Fourier transform infrared (FT-IR) spectroscopy. The optical energy gap (E-opt.) and the high-frequency refractive index (n) were determined from UV-Vis transmission spectra analysis. AC electrical conductivity and dielectric characterization of the polymer composite films have been investigated. The structural parameters of the inter-planar (d) spacing, crystallite length (D), and the average crystallite separation (R) and the FT-IR spectra indicate strong bonding of La3+ ions with the carbonyl groups of the polymer composite chains. The optical gaps of the films determined by Tauc's relation and optical absorption fitting (ASF) exhibit a slight decrease by increasing La3+ ions content, whereas the refractive indices show a slight increase. High values of the dielectric parameter epsilon ' and dielectric loss epsilon '' were produced in pure PVA/PVP composite polymer films, and they tend to decrease by increasing La3+ ions content in the PVA/PVP composite films due to decreasing directional polarization and ionic polarization in the films with increasing La3+ ions content. The minimum energy loss occurred at 70 kHz and these materials may be selected to be used in energy applications. I-V characteristics show a linear-like ohmic behavior because La ions are bonded well in the structure of polymers and became part of it.