Evolution of Intrinsic and Extrinsic Electron Traps at Grain Boundary during Sintering ZnO Based Varistor Ceramics

Abstract

In this paper, evolution of microstructures, electrical properties and defects of the double Schottky barrier during the sintering process were investigated by quenching ZnO varistor ceramics at different sintering stages. It was found that morphology of the samples changed little when the temperature was below 800 °C. Remarkable enhancement of the Schottky barrier height and electrical properties took place in the temperature range between 600 °C and 800 °C. The Bi-rich intergranular layer changed from β phase to α phase. The interfacial relaxation at depletion/intergranular layers became detectable in the samples. Meanwhile, a distinct relaxation loss peak from electron trapping of interface states was observed instead of two dispersed ones. It indicated that the differences among the Schottky barriers in ZnO varistor ceramics became smaller with the process of sintering, which was also supported by the admittance spectra. In addition, oxygen vacancy was found more sensitive to the sintering process than zinc interstitial. The results could provide guidance for fine manipulating the Schottky barrier and its underlying defect structures by optimizing sintering process.

Effects of Dopants and Processing Parameters on the Properties of ZnO-V2O5-Based Varistors Prepared by Powder Metallurgy: A Review

“…Sintering below 1100 °C can lead to MOVs with an inhomogeneous microstructure, reduced and irregular grain growth of ZnO, a high breakdown field, low nonlinearity, and unsatisfactory repeatability of electrical characteristics, as reported in [ 113 ]. The non-ohmic behavior of MOVs is conferred by the electrostatic potential barriers, known as double Schottky barriers (DSBs), which are created during cooling at the GBs of ZnO [ 114 , 115 , 116 , 117 ].…”

Defect Engineering through Field-Effect-Induced Sensitization of Surface-Confined Grain Coalescence: A Route to Enhanced Electron Mobility in Li-Doped ZnO

“…Recent studies have delved into the role of grain boundaries as potential repositories for defects, emphasizing the microstructural influence on the overall defect architecture in ZnO. 2,12,13 Charge transfer and transport are at the heart of many energy storage and conversion systems, such as batteries, supercapacitors, and photoelectrochemical cells. 14 interstitials, or extrinsic, arising from dopants or impurities, play a paramount role in this.…”

“…Annealing in different environments (oxygen-rich, inert, or hydrogen atmospheres) has been a recurrent theme in the literature, aimed at understanding and controlling the defect states in ZnO. , With the advent of advanced characterization techniques, research trended toward direct imaging and identification of defects, enabling researchers to spatially correlate defect presence with electronic properties of ZnO. Recent studies have delved into the role of grain boundaries as potential repositories for defects, emphasizing the microstructural influence on the overall defect architecture in ZnO. ,, …”

Hydrothermal Synthesis of Zinc Oxide Nanoparticles Using Different Chemical Reaction Stimulation Methods and Their Influence on Process Kinetics

“…Zinc oxide nanoparticles are used as a catalyst in organic synthesis. In the electronics industry, ZnONPs are used to produce semiconductors [ 1 , 2 , 3 , 4 , 5 ], varistors [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ], sensors [ 13 , 14 , 15 , 16 , 17 , 18 ] and transistors [ 19 , 20 , 21 , 22 , 23 , 24 ]. Due to the wide energy gap, 3.37 eV zinc oxide is used as a luminescent material in optoelectronics [ 25 , 26 , 27 , 28 , 29 , 30 ].…”