Lennard-Jones Centre for Computational Materials Science

The effects of doping a grain boundary in ZnO with various concentrations of Bi

Carlsson, JM and Hellsing, B and Domingos, HS and Bristowe, PD (2003) The effects of doping a grain boundary in ZnO with various concentrations of Bi. In: UNSPECIFIED.

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Abstract

We have made a systematic study of the Bi-decoration process in a Sigma = 13 [0 0 0 1] tilt grain boundary in ZnO by first-principles calculations. This grain boundary is taken as a in model system for studying the microscopic properties of commercial Bi-doped ZnO-varistors. The calculations show that the decoration process is strongly site dependent and that there is a considerable segregation energy for the Bi-atoms at low concentration. Increasing the concentration lowers the segregation energy which sets an upper limit of approximately 32% for the Bi-concentration in this grain boundary. This implies that the Bi-atoms stay in the grain boundary region rather than diffusing into the ZnO grains during the manufacturing process, but the maximum Bi-concentration is limited which is consistent with the experimental observations. Bi-impurities in ZnO act as donors at low impurity concentration, but a localized Bi-Bi-bond is formed at higher Bi-concentration in the grain boundary. This Bi-state is located in the band gap of ZnO and it may be responsible for the varistor effect observed in Bi-decorated grain boundaries. (C) 2003 Elsevier Science B.V. All rights reserved.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Uncontrolled Keywords: phase ceramics grain boundaries density functional calculations exchange interface states varistor zinc oxide
Subjects: UNSPECIFIED
Divisions: UNSPECIFIED
Depositing User: Unnamed user with email sms67@eng.cam.ac.uk
Date Deposited: 05 Mar 2014 14:37
Last Modified: 17 Jun 2021 15:40
DOI: 10.1016/S0039-6028(03)00193-6

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