Polaron assisted electrical transport and fertile field emission response in polycrystalline LiNi0.33Co0.33Mn0.33O2 with theoretical insight by density functional theory

• Published in: Journal of alloys and compounds 2022-01, Vol.891, p.162056, Article 162056
• Main Authors: Karmakar, Subrata, Mane, Pratap, Mistari, Chetan D., More, Mahendra A., Chakraborty, Brahmananda, Behera, Dhrubananda
• Format: Article
• Language: English
• Subjects: Combustion synthesis; Current carriers; Density functional theory; Electric fields; Electrode polarization; Electrodes; Electron spin; Electronic properties; Elementary excitations; Emitters; Field emission; Field enhancement factor; Grain boundaries; High temperature; Li-ion nanostructured electrode; Maxwell-Wagner polarization; Nyquist plots; Orbital interaction; Polarization (spin alignment); Polaron transport; Polarons; Polycrystals; Sol-gel processes; Thermal evolution; Work functions; X ray photoelectron spectroscopy
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.162056

•Polycrystalline LiCo0.33Ni0.33Mn0.33O2 is synthesized for electrical transport and field emission study.•Indication of polaron delocalization and Maxwell-Wagner effect is explained from conductivity and dielectric plots.•Intriguing low turn-on field~2.75 V/µm and field enhancement factor (β)~4251 is measured from field emission study.•Strong spin polarization of the O-2p with more contribution from Mn-3d states is confirmed from DFT study. [Display omitted] Polycrystalline LiCo0.33Ni0.33Mn0.33O2 compounds were prepared via a sol-gel auto combustion synthesis route to examine its conduction mechanism with thermal assessment and a new window of its application as a field emitter is explored. The structural modules and molecular footmarks have been confirmed by XRD, Raman, FTIR, XPS and FESEM techniques. The Nyquist plots (Z′vs.Z′′) exhibits significant contribution of electrode solid interface effect with compared to intra and inter granular contribution. The variation of real and imaginary impedance, modulus, and conductivity spectra with thermal evolution is attributed with the creation of a quasi-particle called “polaron” and the migration of small polaron by tunneling/hopping creates localized state in high temperature. However, a weak crossover between small polaron hopping (SPH) and Mott’s variable range hopping (VRH) is observed near 323 K. The colossal dielectric permittivity (ɛr′)~5 × 106 is originated from inhomogeneous electronic conduction process in LiNi0.33Co0.33Mn0.33O2 due to the creation of absorption current in the flimsy grain boundary which leads to the stockpile of charge carriers in the external-electrode sample interface and induces Maxwell-Wagner electrode interfacial polarization. The exquisite field emission properties were discovered in LiNi0.33Co0.33Mn0.33O2 with low turn-on field@ 1 µA/cm2~2.75 V/µm and threshold field@ 10 µA/cm2~4.39 V/µm with field enhancement factor (β)~4251. The structural and electronic properties of LiNi0.33Co0.33Mn0.33O2 and the local work function (φ)~4.94 eV is computed employing the Density functional theory (DFT). It further supports the conduction mechanism due to self-trapping electrons and strong spin polarization of the O-2p state under applied electric field.