Reformed dielectric features in single phase orthorhombic nickel vanadate complex oxides and the significance of the lattice dynamics in the optoelectrical features

Abstract

V(1-x)2Ni3xO5-δ compounds are prepared by high-temperature solid-state reactions for mole fractions x = 0.04, 0.05, and 0.06. Micro-Raman spectrum with an excitation wavelength of 540 nm reveals 12 well-resolved phonon modes corresponding to the orthorhombic alpha-polymorphic phase of Vanadium Pentoxide and an extra vibrational mode excited by the tetravalent vanadium cation. A sharp absorption edge is observed from 500 nm to 650 nm in the diffuse reflectance spectrum with the rate of absorption increasing slightly, directly proportional to the x value. Kubelka-Munk plots reveal band gap reduction due to the negative Moss-Burstein shift that is attributed to the Ni2+ occupancy at the lattice sites creating electron deficiency. Frequency-dependent AC conductivity, studied in the frequency range 1 KHz to 1 MHz at room temperature exhibited DC-like conductivity in the low-frequency region, and the Jonsher Power Law fit gives the σdc values increasing with Ni ion concentration. AC conductivity at 1MHZ shows an elevation from 1.6 × 10−03 Sm−1 through 4.8 × 10−03 Sm−1 reaching 13.6 × 10−03 Sm−1 by increasing the concentration of Ni2+ ions. The dielectric constant at 250 °C, is observed to increase from 395, through 1447 to 2614, for mole fractions 0.04,0.05 and 0.06 respectively making this multivalent vanadate system a potential candidate for optoelectric and solid oxide fuel cell applications.