Electric field emission and anomalies of electrical conductivity above room temperature in heterogeneous NiO-SnO2 nano-ceramic composites

Abstract

Microstructural NiO–SnO2 nano-ceramic matrix was synthesized via a solgel auto-combustion technique with a perspective to investigate its noteworthy electric field emission and temperature-induced conduction anomaly. Exceptional field emission performance of nickel-tin oxide composites was discovered with a low turn-on field of 3.9 V/μm and a threshold field of 5.30 V/μm with a good field emission current density of 110.44 μA/cm2 and current stability. Density functional theory was employed to estimate its local work function (Φ) 3.365 eV, and the field enhancement factor (β) was obtained as 1570 by Fowler–Nordheim plot. The anomalies in conductivity spectra at 523 K were detected by a number of physical properties measurement including impedance, conductivity, dielectric, and differential scanning calorimetry with thermal expansion. These phenomena can be rationalized in terms strain-dependent thermal hysteresis effects and localized/delocalized eg electron with a transition from inferior conductive linkage [Ni2+–O2−–Ni2+] and [Sn2+/Sn4+–O2−–Sn2+/Sn4+] to higher conductive linkage [Ni2+–Ni3+] and [Sn2+–Sn4+] of coupled NiO–SnO2 matrix. The temperature dependence frequency exponent (n), ln τ, Rg, Rgb, Cg, and Cgb support additionally the conduction anomaly behavior, and the variation of dielectric constant (ɛr) and loss (tan δ) with temperature around 523 K has been explained in terms of the reduction of space charge layers due to reversal movement of delocalized eg electrons from the grain boundary limit. The frequency dispersing impedance, conductivity, and dielectric spectra with elevated temperature were also demonstrated to comprehend its conduction mechanism with theoretical correlation.

Molecular dynamics and conduction mechanism of poly(vinyl chloride‐co‐vinyl acetate‐co‐2‐hydroxypropyl acrylate) terpolymer containing ionic liquid

“…The change of conduction mechanism from OLPT to SPT with increasing temperature was reported for ceramics, [77][78][79] glasses, 80 organicinorganic hybrids, 81,82 and polymers. 83,84 The real part of AC-conductivity (σ') can also be described by the random free-energy barrier model proposed by Dyre.…”

Low-Temperature Spin-Canted Magnetism and Bipolaron Freezing Electrical Transition in Potential Electron Field Emitter NdNiO3

“…The ac conductivity exhibits three regions near, below, and above MIT transition temperature ∼178 K. The frequency dependence ac conductivity below T c ∼178 K between 80 and 150 K exhibits some intriguing properties in low-frequency regions than high-frequency regions. The conductivity dispersion phenomena in these regions are analyzed by , where σ s and σ ∞ are the estimated conductivity in low- and high-frequency regions, respectively. The term ω (=2πν) and τ represent the angular frequency and characteristics of relaxation time, respectively.…”

“…The frequency dependence ac conductivity below T c ∼178 K between 80 and 150 K exhibits some intriguing properties in low-frequency regions than high-frequency regions. The conductivity dispersion phenomena in these regions are analyzed by , …”

“…The HRTEM micrographs were collected from the FEI MODEL-TECNAI-TF-30-G2 transmission electron microscope. Magnetic measurement of NdNiO 3 powder samples was performed on a SQUID-VSM, Quantum Design Inc. with external magnetic fields up to 3 T in the temperature range of 10–350 K. The low and high-temperature electrical conductivity of a thin circular pellet was measured by a HIOKI-IM 3570 LCR meter cum impedance analyzer within the frequency range 100 Hz to 1 MHz and within the temperature range 80–400 K. The complete electric field emission set up is described in our previous paper …”

“…Magnetic measurement of NdNiO 3 powder samples was performed on a SQUID-VSM, Quantum Design Inc. with external magnetic fields up to 3 T in the temperature range of 10−350 K. The low and high-temperature electrical conductivity of a thin circular pellet was measured by a HIOKI-IM 3570 LCR meter cum impedance analyzer within the frequency range 100 Hz to 1 MHz and within the temperature range 80−400 K. The complete electric field emission set up is described in our previous paper. 28 Computational Details. We performed the first principles-based calculation using density functional theory (DFT) executed in Quantum Espresso code.…”