Positron annihilation and correlated dielectric property studies of a transition metal oxide-modified quaternary nanocomposite 0.1P2O5–0.4ZnO–0.5(xV2O5–(1−x)MoO3)

Abstract

The intrinsic defect properties and dielectric characteristics of the metal oxide nanocomposite 0.1P2O5–0.4ZnO–0.5(xV2O5–(1−x)MoO3) for x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 have been studied in this work. The samples were prepared through the process of melt quenching and the existence of different functional groups or chemical bonds were studied by Fourier transform infrared spectroscopy. X-ray diffraction patterns and transmission electron microscopic images were used to determine the size, shape, distribution and morphology of the different nanocrystallites, which were found being formed at particular stages of modification. The presence of defects and the development of amorphous glassy networks were verified from positron annihilation measurements. The newly formed nanocrystallites were superimposed over the amorphous glassy matrices and the small intensities of orthopositronium lifetimes indicated the free volume defects developing at the glass-nanocrystallite interfaces. The positron annihilation trapping rates and the trapped positron fraction confirmed that defects appeared mainly as the outcome of the deficiency of cations at the respective sites and vacancy clusters were formed through the process of agglomeration. The porosity, which is a specific feature of the glassy amorphous matrix or network being formed, was evidently reflected by the positron lifetime parameters in the intermediate (x = 0.4–0.6) stages of modification. The dielectric properties of the nanocomposites were measured at various temperatures and frequencies and the dielectric constant (ε/) and dielectric loss (ε//) were found to decrease with rising frequency and increase with the rise in temperature. The investigation of the scaling property of electric modulus revealed temperature independent and composition dependent conductivity or dielectric relaxation mechanism. The correlation among the various measured parameters and the implications are discussed.