This paper deals with the application of ZnO varistors—an area which has not been treated in a systematic way in the literature. The paper starts with a brief description of the fundamental properties comprising the electrical behavior as well as the physics, chemistry, and microstructure of the varistor. These properties then form the basis for defining the application parameters that are directly related to the nonlinear current-voltage characteristics of the varistor. This paper provides a detailed description of these parameters and their relation to microstructure and the processing of the varistor. Finally, a discussion is presented on the reliability of the varistor by considering a grain-boundary defect model which explains both the instability and the stability under use conditions.

Application of Zinc Oxide Varistors

Using the self-consistent orthogonalized linear-combination-of-atomic-orbitals method in the local-density approximation, the electronic structure and the optical properties of three phases of titanium dioxide have been studied. For rutile, the calculated band structure, equilibrium lattice constant, and bulk modulus are in good agreement with other recent calculations and with experimental data. The results on the ground-state properties of anatase and brookite are reported. Compared with the rutile phase, anatase has similar ground-state properties except for a larger band gap, whereas brookite has relatively smaller bulk modulus. The optical properties of these three phases are also calculated using the band-structure results and compared with the available measurements. For the rutile phase, the anisotropic properties of the dielectric function are in good agreement with the reflectance spectroscopy. For the anatase phase, there are very limited experimental optical data for comparison. For the brookite phase, no experimental data are available. Our calculations show subtle differences in the optical properties of these three phases.

Electronic and optical properties of three phases of titanium dioxide: Rutile, anatase, and brookite

A defect model for the grain-boundary barrier has been proposed to explain the phenomena of voltage instability/stability of the ZnO varistor. The key element of the proposed model is the zinc interstitials which are present in the depletion layer as excess zinc, arising from the non-stoichiometric nature of ZnO. Both instability and stability have been described in terms of diffusion of these interstitials in the depletion layer, followed by chemical interactions with defects at the grain-boundary interface. Finally, a large body of experimental data is presented to indirectly validate the proposed defect model.

A Grain-boundary Defect Model for Instability/stability of a ZnO Varistor

The transport of majority carriers through an electrically active grain boundary is treated for the situation where deep traps are an essential feature of the bulk semiconductor. Electrons trapped at the interface are screened by the ionized defect states within the depletion regions and thereby a double Schottky potential barrier is formed. The leakage and nonlinearity of the steady-state current across such a grain boundary depend strongly on the distribution of interface states and on the density of the available screening charge. The ac small-signal conductance and capacitance are governed by both the finite response time of the interface and the deep bulk traps. From measurements of the static and dynamic quantities it is then possible to determine the microscopic parameters of the grain boundary.

Carrier transport through grain boundaries in semiconductors

The high-temperature behavior of both a high-angle twist grain boundary and a free surface on the (110) plane of silicon are investigated using molecular dynamics and the Stillinger-Weber potential. It is found that, above the thermodynamic melting point, melting is nucleated at the grain boundary or surface and propagates through the system with a velocity that increases with temperature. We conclude that, due to the relatively fast nucleation times, melting in real crystals should be initiated at grain boundaries and surfaces, a conclusion that is entirely in accord with experiment.

Molecular-dynamics study of lattice-defect-nucleated melting in silicon.

Grain boundaries in semiconductors

Grain boundaries in semiconductors : proceedings of the Materials Research Society annual meeting, November 1981, Boston Park Plaza Hotel, Boston, Massachusetts, U.S.A.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

G. E. Pike

Author Tools

Chat about Author

Papers

Grain boundaries in semiconductors

Grain boundaries in semiconductors : proceedings of the Materials Research Society annual meeting, November 1981, Boston Park Plaza Hotel, Boston, Massachusetts, U.S.A.