Na2Ti6O13를 도핑한 0.94BaTiO3-0.06(Bi0.5Na0.5)TiO3 세라믹스의 미세구조와 Positive Temperature Coefficient of Resistivity 특성

차유정; 정영훈; 이영진; 백종후; 이우영; 김대준; Yu-Joung Cha; Young-Hun Jeong; Young-Jin Lee; Jong-Hoo Paik; Wu-Young Lee; Dae-Joon Kim

Korean Journal of Materials Research, Vol.20, No.11, 575-580, November, 2010

DOI10.3740/MRSK.2010.20.11.575 Export Citation

Na2Ti6O13를 도핑한 0.94BaTiO3-0.06(Bi0.5Na0.5)TiO3 세라믹스의 미세구조와 Positive Temperature Coefficient of Resistivity 특성

Microstructure and Positive Temperature Coefficient of Resistivity Characteristics of Na2Ti6O13-Doped 0.94BaTiO3-0.06(Bi0.5Na0.5)TiO3 Ceramics

차유정, 정영훈^†, 이영진, 백종후, 이우영¹, 김대준¹

한국세라믹기술원
¹㈜하이엘

Yu-Joung Cha, Young-Hun Jeong^†, Young-Jin Lee, Jong-Hoo Paik, Wu-Young Lee¹, and Dae-Joon Kim¹

Electronic Components Lab., Korea Institute of Ceramic Eng. & Tech., Seoul 153-801, Korea
¹Hiel Corporation, 396-1 Haewol-Li, Soyang-Myeon, Wanju-Kun, Jeonbuk 565-840, Korea

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The microstructure and positive temperature coefficient of resistivity (PTCR) characteristics of 0.1 mol%Na2Ti6O13 doped 0.94BaTiO3-0.06(Bi0.5Na0.5)TiO3 (BBNT-NT001) ceramics sintered at various temperatures from 1200oC to 1350oC were investigated in order to develop eco-friendly PTCR thermistors with a high Curie temperature (TC). Resulting thermistors showed a perovskite structure with a tetragonal symmetry. When sintered at 1200oC, the specimen had a uniform microstructure with small grains. However, abnormally grown grains started to appear at 1250oC and a homogeneous microstructure with large grains was exhibited when the sintering temperature reached 1325oC. When the temperature exceeded 1325oC, the grain growth was inhibited due to the numerous nucleation sites generated at the extremely high temperature. It is considered that Na2Ti6O13 is responsible for the grain growth of the 0.94BaTiO3-0.06(Bi0.5Na0.5)TiO3 ceramics by forming a liquid phase during the sintering at around 1300oC. The grain growth of the BBNT-NT001 ceramics was significantly correlated with a decrease of resistivity. All the specimens were observed to have PTCR characteristics except for the sample sintered at 1200oC. The BBNT-NT001 ceramics had significantly decreased nrt and increased resistivity jump with increasing sintering temperature at from 1200oC to 1325oC. Especially, the BBNT-NT001 ceramics sintered at 1325oC exhibited superior PTCR characteristics of low resistivity at room temperature (122 Ω·cm), high resistivity jump (1.28 × 104), high resistivity temperature factor (20.4%/oC), and a high Tc of 157.9oC.

Keywords:PTCR;Na2Ti6O13;(Bi0.5Na0.5)TiO3;liquid phase;sintering temperature

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