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Electronic Conduction Mechanisms in BaTiO 3 –Ni Composites with Ultrafine Microstructure Obtained by Spark Plasma Sintering
Author(s) -
Yoon Songhak,
Pithan Christian,
Waser Rainer,
Dornseiffer Jürgen,
Xiong Yan,
Grüner Daniel,
Shen Zhijian,
Iwaya Shoichi
Publication year - 2010
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.04011.x
Subject(s) - materials science , spark plasma sintering , microstructure , composite material , relative density , sintering , ceramic , barium titanate , grain size , composite number
Spark plasma sintering (SPS) was used to densify BaTiO 3 –Ni composite powders to relative densities above 92.8%. With the increasing Ni content, a decrease in relative density is observed, suggesting that Ni hampers the consolidation process. The microstructures of the BaTiO 3 –Ni composites were of duplex character. The crystallite size of the BaTiO 3 ‐grains was around 100 nm in average. The ceramic matrix phase of BaTiO 3 surrounded Ni inclusions of approximately 1 μm in diameter that were completely incorporated without the formation of any elongated metallic filaments. The ac conductivity of these BaTiO 3 –Ni composites increased with increasing Ni content and with temperature. The dominant conduction mechanisms in SPSed BaTiO 3 –Ni composites showed quite a complicated behavior. A gradual change from band conduction of trapped electrons in oxygen vacancies to a hopping‐type motion of small polarons between Ti 4+ and Ti 3+ is suggested to occur, when the Ni content increases. The influence of oxygen vacancies and other lattice defects on the electrical properties of BaTiO 3 –Ni composites is discussed.