Structural, Optical, and Dielectric Properties of BaTiO₃/Graphene/PVA Hybrid Composite Films

BaTiO₃/graphene/PVA hybrid composite films were fabricated by a solution-casting approach and systematically investigated to establish crystal–polymer interface effects on their structural and functional behavior. X-ray diffraction confirmed the presence of tetragonal BaTiO₃ (P4mm) nanocrystallites with sizes of 13.4–17.0 nm and microstrain ε ≈ 0.114%, embedded within an amorphous PVA matrix and accompanied by a weak graphene (002) reflection. Semi-quantitative RIR evaluation revealed a three-phase composition of BaTiO₃ ≈ 20.7 wt%, graphene ≈ 17.5 wt%, and PVA ≈ 61.8 wt%. SEM imaging showed a heterogeneous layered morphology with platelet-like regions (23–42 μm) and localized agglomerates, indicating non-uniform filler dispersion and high interfacial area density. FTIR and Raman spectra confirmed the coexistence of PVA vibrational modes, graphene domains, and BaTiO₃ lattice vibrations, evidencing strong interactions at phase boundaries.

Optical measurements demonstrated wide band-gap behavior with direct and indirect transitions at 6.38 eV and 6.06 eV, respectively, and ~50% visible-range transparency. Dielectric spectroscopy revealed pronounced Maxwell–Wagner–Sillars interfacial polarization at low frequencies, decreasing dielectric losses with increasing frequency, and AC conductivity transitioning from quasi-DC behavior to dispersive hopping at high frequencies. Temperature-dependent permittivity and conductivity further confirmed thermally activated interfacial and carrier-transport processes.

These results show that crystallite size, phase distribution, and interfacial heterogeneity dominate the functional response of the BaTiO₃/graphene/PVA hybrid, demonstrating its potential for transparent dielectric layers and UV-optoelectronic components within advanced composite crystalline material platforms.