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http://dx.doi.org/10.4191/KCERS.2009.46.3.330

Effects of the Re-oxidation Temperature and Time on the PTC Properties of Sm-doped BaTiO3  

Chung, Yong-Keun (Division of Materials Science Engineering, Hanyang University)
Choi, Sung-Churl (Division of Materials Science Engineering, Hanyang University)
Publication Information
Journal of the Korean Ceramic Society / v.46, no.3, 2009 , pp. 330-335 More about this Journal
Abstract
We investigated the effects of the re-oxidation temperature and time on the positive temperature coefficient (PTC) of resistivity characteristics of Sm-doped $BaTiO_3$ sintered at $1200{\sim}1260^{\circ}C$ for 2 h in a reducing atmosphere (3% $H_2/N_2$), followed by re-oxidization processes in air, in which re-oxidization temperature and time were $600{\sim}1000^{\circ}C$ and $1{\sim}10$h, respectively. The result reveals that Smdoped (Ba,Ca)$TiO_3$ ceramics fired in a reducing atmosphere exhibit low PTC characteristics, whereas the sample re-oxidized at $800^{\circ}C$ for 1 h in air exhibit pronounced PTC characteristics. The room-temperature resistivity and jumping characteristics of resistivity (${\rho}_{max}/{\rho}25^{\circ}C$) decrease with Sm contents. The PTC characteristics with reoxidization time at $800^{\circ}C$ have improved about $2{\sim}3$ orders of magnitude whereas differed according to the sintering temperature. The 0.7 at% Sm-doped (Ba,Ca)$TiO_3$ samples reveal the best PTC characteristics in the present range of formula and processes.
Keywords
$BaTiO_3$; PTC thermistor; $Sm_2O_3$ contents; Reduced atmosphere; Re-oxidization;
Citations & Related Records

Times Cited By SCOPUS : 2
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