BROWSE

Related Researcher

Author's Photo

Jung, Jae-Il
Nano Energy Storage Materials Lab
Research Interests

ITEM VIEW & DOWNLOAD

Thermal runaway, flash sintering and asymmetrical microstructural development of ZnO and ZnO-Bi2O3 under direct currents

Cited 1 times inthomson ciCited 0 times inthomson ci
Title
Thermal runaway, flash sintering and asymmetrical microstructural development of ZnO and ZnO-Bi2O3 under direct currents
Author
Zhang, YuanyaoJung, Jae-IlLuo, Jian
Issue Date
2015-08
Publisher
PERGAMON-ELSEVIER SCIENCE LTD
Citation
ACTA MATERIALIA, v.94, pp.87 - 100
Abstract
DC flash sintering of both pure and 0.5 mol.% Bi2O3-doped ZnO at a relatively high activating field of 300 V/cm has been investigated. It is demonstrated that even high-purity ZnO single crystals can "flash" at similar to 870 degrees C. In comparison, flash sintering occurs at a substantially lower onset temperature of similar to 550 degrees C in ZnO powder specimens, indicating the important roles of surfaces and/or grain boundaries. A model has been developed to forecast the thermal runaway conditions and the predictions are in excellent agreements with the observed onset flash temperatures, attesting that the flash starts as a thermal runaway in at least these ZnO based systems. Interestingly, enhanced grain growth is observed at the anode side of the pure ZnO specimens with an abrupt change in the grain sizes, indicating the occurrence of electric-potential-induced abnormal grain growth. With a large current density, the growth of aligned hexagonal single-crystalline rods toward the anode direction is evident in the ZnO powder specimen. Moreover, Bi2O3 doping defers the onset of flash sintering, which can be explained from the formation of space charges at grain boundaries, and it homogenizes the microstructure due to a liquid-phase sintering effect. The key scientific contributions of this study include the development of a model to predict the thermal runaway conditions that are coincident with the observed onset flash sintering temperatures, the clarification of how flash starts in ZnO based specimens, and the observation and explanation of diversifying phenomena of sintering and microstructural development under applied electric currents. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
URI
https://scholarworks.unist.ac.kr/handle/201301/17004
URL
http://www.sciencedirect.com/science/article/pii/S1359645415002608
DOI
10.1016/j.actamat.2015.04.018
ISSN
1359-6454
Appears in Collections:
ECHE_Journal Papers
Files in This Item:
There are no files associated with this item.

find_unist can give you direct access to the published full text of this article. (UNISTARs only)

Show full item record

qrcode

  • mendeley

    citeulike

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

MENU