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

Polymer rare-earth composite films PVA/PVP –x La 3+ ( x wt%; 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 La 3+ 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 La 3+ 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 La 3+ ions content, whereas the refractive indices show a slight increase. High values of the dielectric parameter ε ′ and dielectric loss ε ″ were produced in pure PVA/PVP composite polymer films, and they tend to decrease by increasing La 3+ ions content in the PVA/PVP composite films due to decreasing directional polarization and ionic polarization in the films with increasing La 3+ 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.