Optical transmission and reflection measurements of highly oriented nanocrystalline K x V 2 O 5 ÁnH 2 O films (0 B x \ 0.01) were studied. The optical constants such as, refractive index, the extinction coefficient, absorption coefficient, optical band gap have been calculated. The optical spectra of all samples exhibited two distinct regions of optical gap, E op1 suggesting a direct allowed transition with optical gap ranging from 0.37 up to 0.42 eV and E op2 suggesting a direct forbidden transition with optical gap ranging from 2.02 up to 2.23 eV. This indicates that K x V 2 O 5 ÁnH 2 O films have more than one type of conduction mechanism.

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For energy storage applications, a material that has high dielectric permittivity, low loss factor, strong thermal resistance, easy processability, and low cost are highly desirable. In the present study, PVA/xNiO nanocomposite films with different NiO contents of (0, 10, 50 and 100) wt% were prepared by casting technology. The PVA/xNiO of 50 wt% NiO has been irradiated with 3 MeV electron beam at a dose of 50 kGy at room temperature in order to investigate the modifications induced in its dielectric properties. The results show that the NiO nanoparticles are well incorporated inside the PVA matrix and the crystallite size of NiO has been decreased upon doping by 50 wt% NiO from 15.45 to 11.44 nm. Also, PVA/(50%)NiO nanocomposite show indirect allowed optical transition (3.43 eV) with relatively high dielectric constant (7.60 to 9.55) and low loss factor (< 0.1) at high frequency (1 MHz) and the entire indicated range of temperature which proposes to use this material in energy storage applications. The electron beam radiation has increased the dielectric constant (10.52 to 13.94) which is preferable. However, a slight increase is observed in the loss factor (< 0.109).

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