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(Co, Nb, Sm)‐Doped Tin Dioxide Varistor Ceramics Sintered Using Nanopowders Prepared by Coprecipitation Method
Author(s) -
Bastami Hajieh,
TaheriNassaj Ehsan,
Smet Philippe F.,
Korthout Katleen,
Poelman Dirk
Publication year - 2011
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.1551-2916.2011.04467.x
Subject(s) - coprecipitation , materials science , varistor , microstructure , sintering , doping , tin dioxide , grain boundary , ceramic , scanning electron microscope , tin , metallurgy , analytical chemistry (journal) , mineralogy , chemical engineering , composite material , chemistry , physics , optoelectronics , chromatography , quantum mechanics , voltage , engineering
(Co, Nb, Sm)‐doped SnO 2 ‐based ceramic with varistor characteristics was successfully fabricated by a conventional sintering of nanosized (Co, Nb, Sm)‐doped SnO 2 powders prepared by coprecipitation method. Values of α∼38 and E B =1430 V/mm were obtained for the varistor doped with 0.05 mol % Sm 2 O 3 , sintered at 1200°C for 1 h. Microstructure development was studied by scanning and transmission electron microscopy, elemental analysis, and X‐ray diffraction. The mean grain size of the SnO 2 ‐based varistor was 1.75 μm. No other phase besides SnO 2 was observed in the varistor doped with 0.05 mol % Sm 2 O 3 . The presence of Nb, Co, and Sm inside the SnO 2 grains confirmed the formation of solid solution. No segregation of Nb was observed and Nb atoms were homogeneously distributed. The excess amounts of Co were segregated at triple‐junctions between SnO 2 grains. A Sm‐rich region with a typical thickness of 65 nm was observed at the grain boundary of the varistor.