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ISSN : 1225-0562(Print)
ISSN : 2287-7258(Online)
Korean Journal of Materials Research Vol.30 No.7 pp.343-349

Comparison of Abnormal Grain Growth Behavior of Lead-Free (Na,K)NbO3-M(Cu,Nb)O3, (M = Ca, Sr, Ba) Piezoelectric Ceramics

Seungwoon Jung,Ji-Ho Lim,Han-Bo Jung,Sung-Yub Ji,Seunggon Choi,Dae-Yong Jeong
Department of Materials Science and Engineering, Inha University, 100 Inha-ro, Incheon 22212, Republic of Korea
Corresponding author E-Mail : (D.-Y. Jeong, Inha Uviv.)


NKN [(Na,K)NbO3] is a candidate lead-free piezoelectric material to replace PZT [Pb(Zr,Ti)O3]. A single crystal has excellent piezoelectric-properties and its properties are dependent of the crystal orientation direction. However, it is hard to fabricate a single crystal with stoichiometrically stable composition due to volatilization of sodium during the growth process. To solve this problem, a solid solution composition is designed (Na,K)NbO3-Ba(Cu,Nb)O3 and solid state grain growth is studied for a sizable single crystal. Ceramic powders of (Na,K)NbO3-M(Cu,Nb)O3 (M = Ca, Sr, Ba) are synthesized and grain growth behavior is investigated for different temperatures and times. Average normal grain sizes of individual specimens, which are heat-treated at 1,125 oC for 10 h, are 6.9, 2.8, and 1.6 m for M = Ca, Sr, and Ba, respectively. Depending on M, the distortion of NKN structure can be altered. XRD results show that (NKN-CaCuN: shrunken orthorhombic; NKN-SrCuN: orthorhombic; NKN-BaCuN: cubic). For the sample heat-treated at 1,125 oC for 10 h, the maximum grain sizes of individual specimens are measured as 40, 5, and 4,000 m for M = Ca, Sr, and Ba, respectively. This abnormal grain size is related to the partial melting temperature (NKN-CaCuN: 960 oC; NKN-SrCuN: 971 oC; NKN-BaCuN: 945 oC).

비납계 (Na,K)NbO3-M(Cu,Nb)O3, (M = Ca, Sr, Ba) 압전 세라믹의 비정상 결정 성장 거동 비교

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